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Age-related changes in word retrieval: Role of bilateral frontal and subcortical networks
Abstract
Healthy older adults frequently report word-finding difficulties, yet the underlying cause of these problems is not well understood. This study examined whether age-related changes in word retrieval are related to changes in areas of the frontal lobes thought to subserve word retrieval or changes in areas of the inferior temporal lobes thought to be involved in semantic knowledge. Twenty younger and 20 older healthy adults named aloud photographs during event-related fMRI. Results showed that in the face of equivalent naming accuracy, older adults activated a larger frontal network than younger adults during word retrieval, but there were no activity differences between groups in the fusiform gyrus, suggesting that the substrates for word retrieval but not for semantic knowledge change with aging. Additionally, correlations between BOLD response and naming accuracy and response latency were found in several frontal and subcortical regions in older adults. Findings are discussed in the context of possible compensatory mechanisms invoked to maintain performance in healthy aging, and suggest that increased involvement of the right hemisphere is not universally beneficial to performance.
... Compared with attention or memory, the relative preservation of language throughout the lifetime [9] may be justified by the need to maintain successful communication, resulting in compensatory, flexible or atypical recruitment of neural resources [1]. Accuracy in semantic tasks is generally well maintained in older adults given their more extensive experience with word use and larger vocabulary than younger adults [1,5,8,[10][11][12][13]. Response times (RTs), however, are often longer than in younger adults [10], possibly because older adults are slower at accessing and retrieving conceptual representations from their semantic store [14][15][16], engaging the required executive function resources [17], and making the necessary motor responses [18]. Aside from behavioral performance, findings reported in the literature about the neural correlates sustaining older adults' versus younger adults' semantic memory are often conflicting, depending on the task used, interindividual variability and the specific age group. ...
... The neural correlates sustaining semantic memory are thought to be largely age-invariant, with only small differences in neural recruitment as a function of age [16,22,[63][64][65][66]. In a recent meta-analysis of 47 neuroimaging studies comparing younger and older people, more activation in semantic control regions was reported in older adults than in younger ones, while accuracy was found to be equal between the two groups [22]. ...
... In a picture-naming task, older adults recruited larger frontal areas than younger ones in both hemispheres. Although recruitment of the IFG bilaterally-and not solely in the left hemisphere-was beneficial to older participants' performance, the recruitment of other right-hemisphere regions was negatively correlated with accuracy [16]. These authors provided support for the claim that the neural substrates of semantic memory representations are intact in older adults, whereas it is the executive aspects of language functions, including accessing and manipulating verbal information, that are most affected by aging [16]. ...
Semantic memory representations are generally well maintained in aging, whereas semantic control is thought to be more affected. To explain this phenomenon, this study tested the predictions of the Compensation-Related Utilization of Neural Circuits Hypothesis (CRUNCH), focusing on task demands in aging as a possible framework. The CRUNCH effect would manifest itself in semantic tasks through a compensatory increase in neural activation in semantic control network regions but only up to a certain threshold of task demands. This study compares 39 younger (20–35 years old) with 39 older participants (60–75 years old) in a triad-based semantic judgment task performed in an fMRI scanner while manipulating task demand levels (low versus high) through semantic distance. In line with the CRUNCH predictions, differences in neurofunctional activation and behavioral performance (accuracy and response times) were expected in younger versus older participants in the low- versus high-demand conditions, which should be manifested in semantic control Regions of Interest (ROIs). Our older participants had intact behavioral performance, as proposed in the literature for semantic memory tasks (maintained accuracy and slower response times (RTs)). Age-invariant behavioral performance in the older group compared to the younger one is necessary to test the CRUNCH predictions. The older adults were also characterized by high cognitive reserve, as our neuropsychological tests showed. Our behavioral results confirmed that our task successfully manipulated task demands: error rates, RTs and perceived difficulty increased with increasing task demands in both age groups. We did not find an interaction between age group and task demand, or a statistically significant difference in activation between the low- and high-demand conditions for either RTs or accuracy. As for brain activation, we did not find the expected age group by task demand interaction, or a significant main effect of task demand. Overall, our results are compatible with some neural activation in the semantic network and the semantic control network, largely in frontotemporoparietal regions. ROI analyses demonstrated significant effects (but no interactions) of task demand in the left and right inferior frontal gyrus, the left posterior middle temporal gyrus, the posterior inferior temporal gyrus and the prefrontal gyrus. Overall, our test did not confirm the CRUNCH predictions.
... vocabulary, word retrieval) are among the most stable cognitive domains throughout the lifespan, remaining better preserved with aging (e.g. Wierenga et al. 2008;Kahlaoui et al. 2012;Hartshorne and Germine 2015). While verbal f luency shows early age-related changes in performance, starting from the age of 50 (e.g. ...
... Research sought to relate these age-related behavioral changes to anatomical and functional neural changes. Age-related changes in both brain structure (Raz 2005;Raz et al. 2005Raz et al. , 2010 Wierenga et al. (2008) and Hoyau et al. (2017) showed larger activation of the frontal network in older adults (starting from around 70 years old) during word retrieval. These findings suggest that substrates involved in word retrieval decline with aging, and must be compensated with additional neural recruitment. ...
... In addition, several fMRI studies reported significant differences between the brain activations of young and older adults in language production tasks, even when behavioral performance was equivalent across age groups (e.g. Wierenga et al. 2008;Meinzer et al. 2009;Diaz et al. 2014;Hoyau et al. 2017;Methqal et al. 2019). Generally, increased and/or more widespread brain activations in older adults (around 70 years old), compared to young adults (around 25 years old), are interpreted as compensatory activity when it is associated with better performance (Cabeza 2002;Reuter-Lorenz 2002) and simply as dedifferentiation when associated with worse performance (Bernard and Seidler 2012). ...
Behavioral and brain-related changes in word production have been claimed to predominantly occur after 70 years of age. Most studies investigating age-related changes in adulthood only compared young to older adults, failing to determine whether neural processes underlying word production change at an earlier age than observed in behavior. This study aims to fill this gap by investigating whether changes in neurophysiological processes underlying word production are aligned with behavioral changes. Behavior and the electrophysiological event-related potential patterns of word production were assessed during a picture naming task in 95 participants across five adult lifespan age groups (ranging from 16 to 80 years old). While behavioral performance decreased starting from 70 years of age, significant neurophysiological changes were present at the age of 40 years old, in a time window (between 150 and 220 ms) likely associated with lexical-semantic processes underlying referential word production. These results show that neurophysiological modifications precede the behavioral changes in language production; they can be interpreted in line with the suggestion that the lexical-semantic reorganization in mid-adulthood influences the maintenance of language skills longer than for other cognitive functions.
... Language production, in particular, is characterized by a left-lateralized frontal-temporal brain network (Hickok & Poeppel, 2007;Indefrey & Levelt, 2004;Price, 2010). However, older adults often show broader patterns of activation, particularly in prefrontal regions, with decreased lateralization (Destrieux et al., 2012;Diaz et al., 2014;Diaz et al., 2019;Diaz et al., 2016;Nagels et al., 2012;Rizio et al., 2017;Wierenga et al., 2008;Zhang et al., 2019). For instance, older adults often show increased involvement of domain-general frontal-parietal regions that belong to the multiple-demand network (Grady et al., 2010;Hoffman & Morcom, 2018). ...
... Compensatory accounts generally argue that age-related increases in activation, via the recruitment of additional regions, serve to compensate for neural declines elsewhere. For example, some evidence suggests that increased activation in right inferior frontal gyrus, which has been associated with executive function, helps older adults maintain performance during language processing (e.g., Baciu et al., 2016;Davis et al., 2014;Persson et al., 2004;Wierenga et al., 2008). Dedifferentiation accounts, on the other hand, argue that the aging brain becomes less efficient and organized, and age-related increases in activation reflect lower levels of inhibition and contribute to a noisier signal overall. ...
... Language production often involves not only the language network, but also regions in the MD networkone of the key reasons that we examined both of these networks. Moreover, in fMRI studies with explicit language tasks, older adults often engage MD network regions to a greater extent than younger adults (Destrieux et al., 2012;Diaz et al., 2014;Diaz et al., 2019;Diaz et al., 2016;Nagels et al., 2012;Rizio et al., 2017;Wierenga et al., 2008;Zhang et al., 2019). Hence, age differences in the MD network were expected to be at least as salient as in the language network. ...
Older adults typically report increased difficulty with language production, while its neural bases are less clear. The current study investigated the neural bases of age-related differences in language production at the word level and the modulating effect of task difficulty, focusing on task-based functional connectivity. Using an English phonological Go/No-Go picture naming task, task difficulty was manipulated by varying the proportion of naming trials (Go trials) and inhibition trials (No-Go trials) across runs. Behaviorally, compared to younger adults, older adults performed worse, and showed larger effects of task difficulty. Neurally, older adults had lower within language network connectivity compared to younger adults. Moreover, older adults' language network became less segregated as task difficulty increased. These results are consistent with the Compensation-Related Utilization of Neural Circuits Hypothesis, suggesting that the brain becomes less specified and efficient with increased task difficulty, and that these effects are stronger among older adults (i.e., more dedifferentiated).
... For neuroimaging studies of language in which young adults show lateralized activity, older adults frequently demonstrate recruitment of additional regions in the contralateral hemisphere [5,[16][17][18][19] in addition to robust activation in the left perisylvian cortex [5,[20][21][22]. This increase in bilateral activity in older adults relative to young adults is seen in many tasks and is often interpreted in the context of two classic frameworks. ...
... For example, Hoyau et al. [27] found bilateral frontal activity associated with faster response times during an object naming task, and van Ettinger-Veenstra et al. [28] showed that higher reading test scores were positively associated with the activity in right posterior temporal cortex. By contrast, a negative correlation was found between right frontal activity and performance on tasks related to picture naming [19], semantic fluency [18], or rhythm-judgment [29]. Intriguingly, Geva and colleagues [29] interpreted a negative correlation between right frontal activity and task performance as supporting a compensatory role of the right hemisphere. ...
... The correlation plot is for visualization of the significant clusters found by the whole-brain multiple regression, in which activity was averaged across voxels within a significant cluster. enga et al. [19] reported a negative correlation between right frontal activity and picture naming accuracy. Meinzer et al. [18] also found the same relationship between right frontal activity and semantic fluency. ...
We investigated how the aging brain copes with acoustic and syntactic challenges during spoken language comprehension. Thirty-eight healthy adults aged 54 – 80 years (M = 66 years) participated in an fMRI experiment wherein listeners indicated the gender of an agent in short spoken sentences that varied in syntactic complexity (object-relative vs subject-relative center-embedded clause structures) and acoustic richness (high vs low spectral detail, but all intelligible). We found widespread activity throughout a bilateral frontotemporal network during successful sentence comprehension. Consistent with prior reports, bilateral inferior frontal gyrus and left posterior superior temporal gyrus were more active in response to object-relative sentences than to subject-relative sentences. Moreover, several regions were significantly correlated with individual differences in task performance: Activity in right frontoparietal cortex and left cerebellum (Crus I & II) showed a negative correlation with overall comprehension. By contrast, left frontotemporal areas and right cerebellum (Lobule VII) showed a negative correlation with accuracy specifically for syntactically complex sentences. In addition, laterality analyses confirmed a lack of hemispheric lateralization in activity evoked by sentence stimuli in older adults. Importantly, we found different hemispheric roles, with a left-lateralized core language network supporting syntactic operations, and right-hemisphere regions coming into play to aid in general cognitive demands during spoken sentence processing. Together our findings support the view that high levels of language comprehension in older adults are maintained by a close interplay between a core left hemisphere language network and additional neural resources in the contralateral hemisphere.
... It has been suggested that activity during language production in aging plays a compensatory role, assisting a declining left hemisphere with language tasks such as word finding (e.g., Cabeza, 2001Cabeza, , 2002Cabeza et al., 2004;Dolcoss et al., 2002). Increased R frontal activity has been shown for older relative to younger adults both for picture naming (Berlinger et al., 2013;Fridriksson et al., 2006;Houyau et al., 2017;Wierenga et al., 2008) and for category-member generation (Persson et al., 2004;Meinzer et al., 2009;Meinzer et al., 2012). ...
... Usually this increased R frontal activity for older adults is located in R pars triangularis (PTr), the anterior portion of the R hemisphere homologue for Broca's area, though not always exclusively so. Wierenga et al. (2008) found that for poorer performing older adults, picture naming was negatively correlated with BOLD activity in R PTr (Wierenga et al., 2008). More importantly, Meinzer et al. (2009) and Meinzer et al. (2012) found for all older adults that accuracy of category-member generation was negatively correlated with R PTr BOLD activity during this task. ...
... Usually this increased R frontal activity for older adults is located in R pars triangularis (PTr), the anterior portion of the R hemisphere homologue for Broca's area, though not always exclusively so. Wierenga et al. (2008) found that for poorer performing older adults, picture naming was negatively correlated with BOLD activity in R PTr (Wierenga et al., 2008). More importantly, Meinzer et al. (2009) and Meinzer et al. (2012) found for all older adults that accuracy of category-member generation was negatively correlated with R PTr BOLD activity during this task. ...
1 Hz rTMS was used to decrease excitability of right pars triangularis (R PTr) to determine whether increased R PTr activity during picture naming in older adults hampers word finding. We hypothesized that decreasing R PTr excitability would reduce interference with word finding, facilitating faster picture naming. 15 older and 16 younger adults received two rTMS sessions. In one, speech onset latencies for picture naming were measured after both sham and active R PTr stimulation. In the other session, sham and active stimulation of a control region, right pars opercularis (R POp), were administered before picture naming. Order of active vs. sham stimulation within session was counterbalanced. Younger adults showed no significant effects of stimulation. In older adults, a trend indicated that participants named pictures more quickly after active than sham R PTr stimulation. However, older adults also showed longer responses during R PTr than R POp sham stimulation. When order of active vs. sham stimulation was modeled, older adults receiving active stimulation first had significantly faster responding after active than sham R PTr stimulation and significantly faster responding after R PTr than R POp stimulation, consistent with experimental hypotheses. However, older adults receiving sham stimulation first showed no significant differences between conditions. Findings are best understood, based on previous studies, when the interaction between the excitatory effects of picture naming and the inhibitory effects of 1 Hz rTMS on R PTr is considered. Implications regarding right frontal activity in older adults and for design of future experiments are discussed.
... In addition to age-related behavioral differences, functional neuroimaging studies have also shown that older adults often elicit different patterns of functional activation such as increased bilateral activation and increased activation in prefrontal regions compared to younger adults (Cabeza, 2002;Cabeza and Dennis, 2012;Davis et al., 2008;Grady et al., 2015;Langenecker and Nielson, 2003;Logan et al., 2002;Wierenga et al., 2008). Specific to language, while younger adults typically engage a left-lateralized network, especially during language production (Hickok and Poeppel, 2007;Indefrey and Levelt, 2004;Price, 2010), older adults often show less lateralized patterns of fMRI activation compared to younger adults (Destrieux et al., 2012;Diaz et al., 2014;Diaz et al., 2019;Diaz et al., 2016;Nagels et al., 2012;Rizio et al., 2017;Wierenga et al., 2008;Zhang et al., 2019). ...
... In addition to age-related behavioral differences, functional neuroimaging studies have also shown that older adults often elicit different patterns of functional activation such as increased bilateral activation and increased activation in prefrontal regions compared to younger adults (Cabeza, 2002;Cabeza and Dennis, 2012;Davis et al., 2008;Grady et al., 2015;Langenecker and Nielson, 2003;Logan et al., 2002;Wierenga et al., 2008). Specific to language, while younger adults typically engage a left-lateralized network, especially during language production (Hickok and Poeppel, 2007;Indefrey and Levelt, 2004;Price, 2010), older adults often show less lateralized patterns of fMRI activation compared to younger adults (Destrieux et al., 2012;Diaz et al., 2014;Diaz et al., 2019;Diaz et al., 2016;Nagels et al., 2012;Rizio et al., 2017;Wierenga et al., 2008;Zhang et al., 2019). ...
... Although others have reported age-related increases in ALFF in other regions (Mather and Nga, 2013), ours is the first to show this age association in a resting-state language network. This finding of age-related increases in ALFF is also broadly consistent with age-related increases in task-based functional activation that are often reported (Cabeza and Dennis, 2012;Persson et al., 2004;Wierenga et al., 2008;Zhang et al., 2019). ...
Neuroimaging studies often either look at functional activation in response to an explicit task, or functional connectivity (i.e., interregional correlations) during resting-state. Few studies have looked at the intensity of brain activity or its relationship with age, behavior, and language. The current study investigated both intensity (i.e., the Amplitude of Low-Frequency Fluctuations, ALFF) and the functional connectivity of spontaneous brain activity during rest and their relationship with age and language. A life-span sample of individuals (N = 152) completed a battery of neuropsychological tests to assess basic cognitive functions and resting-state functional MRI data to assess spontaneous brain activity. Focusing on an extend language network, the mean ALFF and total degree were calculated for this network. We found that increased age was associated with more intense activity (i.e., higher ALFF) but lower within-network connectivity. Additionally, these increases in activity within the language network during resting-state were related to worse language ability, particularly in younger adults, supporting a dedifferentiation account of cognition. Our results support the utility of using resting-state data as an indicator of cognition and support the role of ALFF as a potential biomarker in characterizing the relationships between resting-state brain activity, age, and cognition.
... In the realm of language function, age-related decline in word retrieval is also a frequently observed phenomenon (Burke and Shafto, 2004). The few task fMRI studies that have addressed language production mechanisms (Meinzer et al., 2009;Shafto et al., 2010;Soros et al., 2011) have shown increased frontal activation in older adults (Wierenga et al., 2008). In the context of overt word production tasks, agingrelated differences in biphasic BOLD hemodynamic response function (HRF) have been reported by a previous study (Wierenga et al., 2008). ...
... The few task fMRI studies that have addressed language production mechanisms (Meinzer et al., 2009;Shafto et al., 2010;Soros et al., 2011) have shown increased frontal activation in older adults (Wierenga et al., 2008). In the context of overt word production tasks, agingrelated differences in biphasic BOLD hemodynamic response function (HRF) have been reported by a previous study (Wierenga et al., 2008). However, it is unclear whether the previously reported age-related increase in frontal activity, and language-specific biphasic BOLD activity were more weighted by task-specific neural changes or neural changes masked by baseline physiology. ...
... The smoothed BOLD time course was scaled with respect to the initial 12 s active baseline condition (repeating "REST") to obtain task-induced relative % BOLD change, censored for head motion (>0.3 mm), followed by a deconvolution (AFNI's 3dDeconvolve using 13 TENT functions between −4 and 44 s) to estimate the HRF of the 8-trial block. The HRF length was estimated to require 48 s to return to baseline by using a Matlab simulation of this study's task design in conjunction with a biphasic impulse response function derived from a previous overt language task fMRI study (Wierenga et al., 2008). In order to account for low frequency scanner drifts, we employed the polynomial fitting option within AFNI's 3dDeconvolve command. ...
Blood Oxygen Level Dependent (BOLD) functional MRI is a complex neurovascular signal whose magnitude depends on baseline physiological factors such as cerebral blood flow (CBF). Because baseline CBF varies across the brain and is altered with aging, the interpretation of stand-alone aging-related BOLD changes can be misleading. The primary objective of this study was to develop a methodology that combines task fMRI and arterial spin labeling (ASL) techniques to sensitize task-induced BOLD activity by covarying out the baseline physiology (i.e., CBF) in an aging model. We recruited 11 younger and 13 older healthy participants who underwent ASL and an overt language fMRI task (semantic category member generation). We measured in-scanner language performance to investigate the effect of BOLD sensitization on BOLD-behavior relationships. The results demonstrate that our correction approach is effective at enhancing the specificity and sensitivity of the BOLD signal in both groups. In addition, the correction strengthens the statistical association between task BOLD activity and behavioral performance. Although CBF has inherent age dependence, our results show that retaining the age factor within CBF aides in greater sensitization of task fMRI signals. From a cognitive standpoint, compared to young adults, the older participants showed a delayed domain-general language-related task activity possibly due to compromised vessel compliance. Further, assessment of functional evolution of corrected BOLD activity revealed biphasic BOLD dynamics in both groups where BOLD deactivation may reflect greater semantic demand or increased premium on domain general executive functioning in response to task difficulty. Although it was promising to note that the predictability of behavior using the proposed methodology outperforms other methodologies (i.e., no correction and normalization by division), and provides moderate stability and adequate power, further work with a larger cohort and other task designs is necessary to improve the stability of predicting associated behavior. In summary, we recommend correction of task fMRI signals by covarying out baseline CBF especially when comparing groups with different neurovascular properties. Given that ASL and BOLD fMRI are well established and widely employed techniques, our proposed multi-modal methodology can be readily implemented into data processing pipelines to obtain more accurate BOLD activation maps.
... In the context of the neural theories of aging introduced above, there have been several fMRI studies conducted specifically on language production that show the general trend of older adults eliciting increased bilateral and frontal activation compared to younger adults (Diaz, Johnson, Burke, & Madden, 2014;Diaz, Johnson, Burke, Truong, & Madden, 2019;Geva et al., 2014;Meinzer et al., 2009;Obler et al., 2010;Rizio, Moyer, & Diaz, 2017;Wierenga et al., 2008;Zhang et al., 2013). However, the function of such increases during language production is still debated because there has been support for both neural dedifferentiation and compensation accounts, and increases in activation often occur outside of core language regions (Diaz et al., 2014;Tremblay, Sato, & Deschamps, 2017;Wierenga et al., 2008). ...
... In the context of the neural theories of aging introduced above, there have been several fMRI studies conducted specifically on language production that show the general trend of older adults eliciting increased bilateral and frontal activation compared to younger adults (Diaz, Johnson, Burke, & Madden, 2014;Diaz, Johnson, Burke, Truong, & Madden, 2019;Geva et al., 2014;Meinzer et al., 2009;Obler et al., 2010;Rizio, Moyer, & Diaz, 2017;Wierenga et al., 2008;Zhang et al., 2013). However, the function of such increases during language production is still debated because there has been support for both neural dedifferentiation and compensation accounts, and increases in activation often occur outside of core language regions (Diaz et al., 2014;Tremblay, Sato, & Deschamps, 2017;Wierenga et al., 2008). For instance, Wierenga and colleagues (2008) reported compensatory patterns in which high-performing older adults elicited increased activation in the right inferior frontal gyrus, a region associated with executive function in general, relative to low-performing older adults during picture naming. ...
... However, activation increases in the right precentral gyrus, a motor control region, correlated with worse behavioral performance in older adults compared to younger adults, suggesting dedifferentiation. These results suggest that not all right hemisphere activation is compensatory, and the particular brain region in which overactivation is found may be important for determining its relationship to behavioral performance (Diaz et al., 2014;Tremblay & Deschamps, 2016;Tremblay et al., 2017;Wierenga et al., 2008). ...
As individuals age, they experience increased difficulties producing speech, especially with infrequent words. Older adults report that word retrieval difficulties frequently occur and are highly frustrating. However, little is known about how age affects the neural basis of language production. Moreover, age-related increases in brain activation are often observed, yet there is disagreement about whether such increases represent a form of neural compensation or dedifferentiation. We used functional magnetic resonance imaging (fMRI) to determine if there are age-related differences in functional activation during picture naming and whether such differences are consistent with a compensatory, dedifferentiation, or hybrid account that factors in difficulty. Healthy younger and older adults performed a picture-naming task with stimuli that varied in lexical frequency—our proxy for difficulty. Both younger and older adults were sensitive to lexical frequency behaviorally and neurally. However, younger adults performed more accurately overall and engaged both language (bilateral insula and temporal pole) and cognitive control (bilateral superior frontal gyri and left cingulate) regions to a greater extent than older adults when processing lower frequency items. In both groups, poorer performance was associated with increases in functional activation consistent with dedifferentiation. Moreover, there were age-related differences in the strength of these correlations, with better performing younger adults modulating the bilateral insula and temporal pole and better performing older adults modulating bilateral frontal pole and precuneus. Overall, these findings highlight the influence of task difficulty on fMRI activation in older adults and suggest that as task difficulty increases, older and younger adults rely on different neural resources.
... While older individuals often complain about proper names retrieval (Condret-Santi et al., 2013), they often obtain accuracy scores similar to younger adults when naming pictures of common names. Yet, this typically occurs at the expense of longer response times (Baciu et al., 2016;Hoyau et al., 2017;Wierenga et al., 2008) in possible relation with a general slowing in information processing (Feyereisen, Demaeght, & Samson, 1998). The dissociation between time and accuracy makes this task particularly interesting as it suggests that older adults engage in adaptive mechanisms to perform it adequately. ...
... Some complain about wordfinding difficulties, but mostly so for proper names and with no relation with objective cognitive difficulty (Condret-Santi et al., 2013). However, on average, their accuracy is preserved, sometimes even improved, when a simple common names task is used, where accuracy and not response time is scored and when there are few time constraints (LaBarge, Edwards, & Knesevich, 1986;Salthouse, 2014;Schmitter-Edgecombe, Vesneski, & Jones, 2000;Verhaegen & Poncelet, 2013;Wierenga et al., 2008). Overall, naming abilities for common names appear behaviorally preserved when task demand is controlled, at least until 65 years of age (Salthouse, 2014). ...
... Although examples of difficulties during naming are common in the literature (Feyereisen, 1997;Goulet et al., 1994;Shafto et al., 2017), mean accuracy is generally preserved in our study, in line with previous reports that examined accuracy with untimed tasks (LaBarge et al., 1986;Salthouse, 2014;Schmitter-Edgecombe et al., 2000;Verhaegen & Poncelet, 2013;Wierenga et al., 2008). In the context of preserved cognitive performance, then, the absence of such "compensatory" activity is not surprising. ...
The topological organization of the brain, governed by the capacity of brain regions to synchronize their activity, allows for cost-effective performance during everyday cognitive activity. Functional connectivity is an fMRI method deemed task-specific and demanddependent. While the brain undergoes significant changes during healthy aging, conceptual knowledge and word production accuracy are generally preserved. The exploration of taskinduced functional connectivity (FC) patterns during active picture naming may thus provide additional information about healthy functional cerebral mechanisms that are specifically adapted to the cognitive activity at hand.
The goal of this study is to assess and describe age-related differences in functional connectivity during an overt picture-naming task, as well as to compare age-related differences under complex task demand, defined by lexical frequency.
Results suggest both age- and task-specific mechanisms. In the context of preserved behavioral performance in a picture-naming task, older adults show a complex array of differences in FC architecture, including both increases and decreases.
In brief, there is increased segregation and specialization of regions classically assigned to naming processes. Results also expand upon previous word production studies and suggest that motor regions are particularly subject to age-related differences. This study also provides the first indication that intrinsic task demand, as manipulated by lexical frequency, interacts little with the relationship between age and FC.
Together, these findings confirm the value of task-induced FC analysis in revealing thebrain organization that subserves task performance during healthy aging.
... Studies also looked at the effects of aging on the language neurocognitive architecture. Wierenga et al. (2008) showed, for instance, that in older individuals, the frontal cortex was more activated in language production tasks, which was associated with a similar level of accuracy (see also Kemper et al., 2001). Since there was no difference in inferior temporal areas, this effect was interpreted in favor of difficulties in retrieval processes rather than changes in long-term memory storage. ...
... Despite a continuously growing vocabulary across the lifespan, accuracy in naming from definition slightly decreases. With regard to language production in older individuals, it has been suggested that difficulties could be related to different semantic associations (Wierenga et al., 2008) or to retrieval abilities, which involve semantic, cognitive, and control processes leading to lexical selection (Braver and Barch, 2002), or inefficient phonological word form retrieval (Burke and Mackay, 1997). ...
Introduction
The ability to speak is grounded in general memory and control processes and likely changes across the lifespan. However, our knowledge on how word production abilities naturally evolve from childhood to old age remains marginally investigated. Our aim was to shed further light on this issue by exploiting the contrast between two ways to elicit word production: referential picture naming and inferential naming from definition.
Methods
We collected accuracy and production latencies in a picture naming task and in a naming from definition task from 130 participants ranging from 10 to 80 years old. Measures of vocabulary size, digit span memory, semantic and phonemic fluencies and processing speed were also collected. We used multivariate adaptative regression splines and regression models to characterize lifespan patterns of the two tasks.
Results
Patterns of increase in performance were similar for picture naming and naming from definition only from childhood to young adulthood. In the second half of the lifespan, significant decrease of performance was found in older adults for picture naming (from around 60 years-old) but not for naming from definition. Clearly, word production elicited with an inferential task (naming from definition) yields different age-related patterns than usually described in the literature with a referential task (picture naming).
Discussion
We discuss how cognitive processes such as visual-conceptual processes and lexical prediction may explain the differential pattern of results in aging in referential and inferential production tasks. We argue for more lifespan studies and the need to investigate language production beyond picture naming, in particular with respect to aging.
... A core example of supportive reorganisation is the increasing bilateral (Cabeza, 2002) activation of the prefrontal regions during cognitively engaging tasks (Davis et al., 2008; see also Maillet and Rajah, 2013;Reuter-Lorenz and Park, 2014) such as rapid word production (Wierenga et al., 2008;Hoyau et al., 2017). However, it remains unclear how neurocognitive ageing impacts speech at large (for reviews, see Shafto and Tyler, 2014;Peelle, 2019). ...
... were analysed for task pairs where age-associated functional reallocation showed a significant laterality change at larger scale. To test for the previously established laterality shift in the (pre-) frontal regions (Cabeza, 2002; see also Wierenga et al., 2008;Hoyau et al., 2017) and whether such an effect would also appear in temporal and parietal auditory-motor vocal production regions (Callan et al., 2006;Özdemir et al., 2006), this fine-grained approach involved MFG (Brainnetome subregions 15-28), IFG (29-40), orbitofrontal (OFG; 41-52) and precentral gyri (PrCG; 53-64) frontally; STG ...
Background
Understanding healthy brain ageing has become vital as populations are ageing rapidly and age-related brain diseases are becoming more common. In normal brain ageing, speech processing undergoes functional reorganisation involving reductions of hemispheric asymmetry and overactivation in the prefrontal regions. However, little is known about how these changes generalise to other vocal production, such as singing, and how they are affected by associated cognitive demands.Methods
The present cross-sectional fMRI study systematically maps the neural correlates of vocal production across adulthood (N=100, age 21–88 years) using a balanced 2x3 design where tasks varied in modality (speech: proverbs / singing: song phrases) and cognitive demand (repetition / completion from memory / improvisation).ResultsIn speech production, ageing was associated with decreased left pre- and postcentral activation across tasks and increased bilateral angular and right inferior temporal and fusiform activation in the improvisation task. In singing production, ageing was associated with increased activation in medial and bilateral prefrontal and parietal regions in the completion task, whereas other tasks showed no ageing effects. Direct comparisons between the modalities showed larger age-related activation changes in speech than singing across tasks, including a larger left-to-right shift in lateral prefrontal regions in the improvisation task.Conclusion
The present results suggest that the brains’ singing network undergoes differential functional reorganisation in normal ageing compared to the speech network, particularly during a task with high executive demand. These findings are relevant for understanding the effects of ageing on vocal production as well as how singing can support communication in healthy ageing and neurological rehabilitation.
... For example, as people age, they often show structural changes in the brain such as decreased grey matter volume (Raz et al., 2005;Sowell et al., 2004), and decreased white matter integrity (Bartzokis et al., 2012;Imperati et al., 2011;Mwangi et al., 2013). In addition to structural brain changes, older and younger adults also exhibit different patterns of task-based functional activation with older adults often showing increases in brain activation (e.g., greater bilateral prefrontal activation, Cabeza & Dennis, 2012;Davis et al., 2008;Diaz et al., 2021;Grady et al., 2015;Wierenga et al., 2008;Zhang et al., 2019). Although age-related differences in functional activation are commonly observed, the mechanism underlying such changes has been debated. ...
... age-related neural differences should be interpreted i.e., as compensatory (Cabeza et al., 2018) or neural dedifferentiation (Li et al., 2001). Specific to neural activities underlying language production, some task-based functional MRI studies have reported patterns supporting compensation (e.g., additional brain activation associated with maintained behavioral performance; Nagels et al., 2012;Wierenga et al., 2008) while others have found evidence for dedifferentiation (e.g., increased brain activation related to weakened behavioral performance; Diaz et al., 2014;Meinzer et al., 2009). In the current study, we focused on resting state functional connectivity and investigated how the network characteristics in the language network and across the whole brain relate to language production across adulthood. ...
Older adults typically exhibit decline in language production. However, how the brain supports or fails to support these processes is unclear. Moreover, there are competing hypotheses about the nature of age-related neural changes, and whether age-related increases in neural activity reflect compensation or a decline in neural efficiency. In the current study, we investigated the neural bases of language production focusing on resting state functional connectivity. We hypothesized that language production performance, functional connectivity, and their relationship would differ as a function of age. Consistent with prior work, older age was associated with worse language production performance. Functional connectivity analyses showed that network segregation within the left hemisphere language network was maintained across adulthood. However, increased age was associated with lower whole brain network segregation. Moreover, network segregation was related to language production ability. In both network analyses, there were significant interactions with age—higher network segregation was associated with better language production abilities for younger and middle-aged adults, but not older adults. Interestingly, there was a stronger relationship between language production and the whole brain network segregation than between production and the language network. These results highlight the utility of network segregation measures as an index of brain function, with higher network segregation associated with better language production ability. Moreover, these results are consistent with stability in the left hemisphere language network across adulthood, and suggest that dedifferentiation among brain networks, outside of the language network, is a hallmark of aging and may contribute to age-related language production difficulties.
... Similar to what has been observed in memory function, word retrieval efficiency also tends to decline with aging [18][19][20][21][22] . In a fMRI study, Wierenga et al. 23 compared activation during a naming task between younger and older adults, controlling 15 years of schooling for both groups. Their results support the HAROLD model as the group of older adults showed more bilateral activations. ...
... Taking together, this data could be understood as the IFG was in charge of monitoring and keeping of verbal working memory span of semantic representations stored in the temporoparietal structures 47 . Wierenga et al. 23 results commented above, compared activation between young and older adults during a picture-naming task. They reported that both groups performed well, and their findings showed that older adults present more activation in the right Broca's area (BA 44,45) and in the right IFG (BA 47) than young adults. ...
Hemispheric asymmetry reduction in older adults (HAROLD) model has claimed that older adults tend to display less lateralized brain activation patterns with respect to younger ones during memory, language, and naming tasks, but only a few times have these patterns been explored within older population. Furthermore, it is unclear if this phenomenon is a compensation response or an adaptive pattern that is not helping cognitive functions. Literature has assumed that education level (EL) could be critical, to explain such patterns. We aimed to control this as a variable by comparing neural correlates with an functional magnetic resonance imaging picture naming task in literate, healthy older adults with high and low EL. Our results showed that EL is not a determinant factor for activation of neural pattern reorganization prognosis. It was found that performance is a more reliable variable to observe neural pattern reorganization in the elderly. This study supports the de-differentiation hypothesis of HAROLD model because there is no reduction in lateralization of some highly-specialized structures in persons who maintained optimal lexical access, in contrast to those who had low scores in naming task.
... Burke & Shafto, 2008;Shafto & Tyler, 2014), such as undermining their confidence and ability to communicate (e.g. Abrams & Farrell, 2011;Wierenga et al., 2008). Moreover, the presence of naming deficits is also indicative of a more precipitous cognitive decline in individuals with naming problems than those without (see De Jager et al., 2005). ...
Older adults frequently report trouble retrieving words, which is often tested by confrontation naming tasks. However, with inconsistencies among the relevant literature, this ageing effect requires an updated meta-analysis (with the only meta-analysis conducted in 1997), especially when no meta-analysis has been conducted on how such an effect may be modulated by the important factor of education. By synthesizing 41 primary studies, the present meta-analysis revealed a significant ageing effect on confrontation naming (indexed by accuracy), which was modulated by participant age and education. First, a significant ageing effect only occurred in participants aged 70 and above (compared with participants below 60). Second, participants with low- and middle-level education exhibited significantly larger ageing effects than those with high-level education. Third, for the age-and-education interaction, an ageing effect occurred as early as 60 in participants in the low-and-middle education level, while this critical age for participants with high-level education is 70.
... A possible explanation for these rather conflicting results may be that elderly make use of different strategies and neural structures to maintain speech comprehension at a functioning level ( Reuter-Lorenz and Cappell, 2008;Tiedt et al., 2020 ). Indeed, evidence suggests that older adults present a more bilaterally organized activation pattern for processing linguistic aspects of speech, whereas younger adults rely more on the left hemisphere ( Diaz et al., 2016;Grossman et al., 2002;Wierenga et al., 2008;Wingfield and Grossman, 2006;Wlotko et al., 2010 ). This finding is yet to be tested via EEG-based NT. ...
Background:
Older adults process speech differently, but it is not yet clear how aging affects different levels of processing natural, continuous speech, both in terms of bottom-up acoustic analysis and top-down generation of linguistic-based predictions. We studied natural speech processing across the adult lifespan via electroencephalography (EEG) measurements of neural tracking.
Goals:
Our goals are to analyze the unique contribution of linguistic speech processing across the adult lifespan using natural speech, while controlling for the influence of acoustic processing. Moreover, we also studied acoustic processing across age. In particular, we focus on changes in spatial and temporal activation patterns in response to natural speech across the lifespan.
Methods:
52 normal-hearing adults between 17 and 82 years of age listened to a naturally spoken story while the EEG signal was recorded. We investigated the effect of age on acoustic and linguistic processing of speech. Because age correlated with hearing capacity and measures of cognition, we investigated whether the observed age effect is mediated by these factors. Furthermore, we investigated whether there is an effect of age on hemisphere lateralization and on spatiotemporal patterns of the neural responses.
Results:
Our EEG results showed that linguistic speech processing declines with advancing age. Moreover, as age increased, the neural response latency to certain aspects of linguistic speech processing increased. Also acoustic neural tracking (NT) decreased with increasing age, which is at odds with the literature. In contrast to linguistic processing, older subjects showed shorter latencies for early acoustic responses to speech. No evidence was found for hemispheric lateralization in neither younger nor older adults during linguistic speech processing. Most of the observed aging effects on acoustic and linguistic processing were not explained by age-related decline in hearing capacity or cognition. However, our results suggest that the effect of decreasing linguistic neural tracking with advancing age at word-level is also partially due to an age-related decline in cognition than a robust effect of age.
Conclusion:
Spatial and temporal characteristics of the neural responses to continuous speech change across the adult lifespan for both acoustic and linguistic speech processing. These changes may be traces of structural and/or functional change that occurs with advancing age.
... language) is a product of compensatory mechanisms in normal aging, i.e. the provision that tasks can be successfully completed with necessary help from the non-dominant hemisphere to the dominant one (Reuter-Lorenz et al., 2000;Cabeza, 2002;Rossi et al., 2004;Philipose et al., 2007;Park and Reuter-Lorenz, 2009;Meier et al., 2011). Others have suggested that contralateral engagement in executive function tends to be related to impaired language function (Wierenga et al., 2008;Meinzer et al., 2009). Additionally, a shift of language function to homologous areas has been demonstrated in a study where regions of the language networks remained structurally intact but were exposed to hypoperfusion from a neighboring subcortical infarct (Prabhakaran et al., 2007). ...
... language) is a product of compensatory mechanisms in normal aging, i.e. the provision that tasks can be successfully completed with necessary help from the non-dominant hemisphere to the dominant one (Reuter-Lorenz et al., 2000;Cabeza, 2002;Rossi et al., 2004;Philipose et al., 2007;Park and Reuter-Lorenz, 2009;Meier et al., 2011). Others have suggested that contralateral engagement in executive function tends to be related to impaired language function (Wierenga et al., 2008;Meinzer et al., 2009). Additionally, a shift of language function to homologous areas has been demonstrated in a study where regions of the language networks remained structurally intact but were exposed to hypoperfusion from a neighboring subcortical infarct (Prabhakaran et al., 2007). ...
... Some researchers have suggested that the neural substrate of naming is primarily lateralized to the left hemisphere and becomes bilateral during the aging process (Cabeza, 2002). Actually, one study comparing naming performance between younger and older adults showed that older participants were more likely to have bilateral activation than younger participants (Wierenga et al., 2008). The other MRI study observed a positive correlation between naming ability and bilateral gray matter volume in older participants (Obler et al., 2010). ...
Objective
Language function test-specific neural substrates in Korean patients with primary progressive aphasia (PPA) might differ from those in other causes of dementia and English-speaking PPA patients. We investigated the correlation between language performance tests and cortical thickness to determine neural substrates in Korean patients with PPA.
Materials and methods
Ninety-six patients with PPA were recruited from the memory clinic. To acquire neural substrates, we performed linear regression using the scores of each language test as a predictor, cortical thickness as an outcome and age, sex, years of education, and intracranial volume as confounders.
Results
Poor performance in each language function test was associated with lower cortical thickness in specific cortical regions: (1) object naming and the bilateral anterior to mid-portion of the lateral temporal and basal temporal regions; (2) semantic generative naming and the bilateral anterior to mid-portion of the lateral temporal and basal temporal regions; (3) phonemic generative naming and the left prefrontal and inferior parietal regions; and (4) comprehension and the left posterior portion of the superior and middle temporal regions. In particular, the neural substrates of the semantic generative naming test in PPA patients, left anterior to mid-portion of the lateral and basal temporal regions, quite differed from those in patients with other causes of dementia.
Conclusion
Our findings provide a better understanding of the different pathomechanisms for language impairments among PPA patients from those with other causes of dementia.
... A possible explanation for these rather conflicting results may be that elderly make use of different strategies and neural structures to maintain speech comprehension at a functioning level ( Reuter-Lorenz and Cappell, 2008;Tiedt et al., 2020 ). Indeed, evidence suggests that older adults present a more bilaterally organized activation pattern for processing linguistic aspects of speech, whereas younger adults rely more on the left hemisphere ( Diaz et al., 2016;Grossman et al., 2002;Wierenga et al., 2008;Wingfield and Grossman, 2006;Wlotko et al., 2010 ). This finding is yet to be tested via EEG-based NT. ...
Background
Older adults process speech differently, but it is not yet clear how aging affects different levels of processing natural, continuous speech, both in terms of bottom-up acoustic analysis and top-down generation of linguistic-based predictions. We studied natural speech processing across the adult lifespan via electroencephalography (EEG) measurements of neural tracking.
Goals
Our goals are to analyze the unique contribution of linguistic speech processing across the adult lifespan using natural speech, while controlling for the influence of acoustic processing. In particular, we focus on changes in spatial and temporal activation patterns in response to natural speech across the lifespan.
Methods
52 normal-hearing adults between 17 and 82 years of age listened to a naturally spoken story while the EEG signal was recorded. We investigated the effect of age on acoustic and linguistic processing of speech. Because age correlated with hearing capacity and measures of cognition, we investigated whether the observed age effect is mediated by these factors. Furthermore, we investigated whether there is an effect of age on hemisphere lateralization and on spatiotemporal patterns of the neural responses.
Results
Our EEG results showed that linguistic speech processing declines with advancing age. Moreover, as age increased, the neural response latency to certain aspects of linguistic speech processing increased. Also acoustic neural tracking (NT) decreased with increasing age but in contrast to linguistic processing, older subjects showed shorter latencies for early acoustic responses to speech. No evidence was found for hemispheric lateralization in neither younger nor older adults during linguistic speech processing. Most of the observed aging effects on acoustic and linguistic processing were not explained by age-related decline in hearing capacity or cognition. However, our results suggest that the effect of increasing neural response latency with age for word-level linguistic processing is likely more due to an age-related decline in cognition than a robust effect of age.
Conclusion
Spatial and temporal characteristics of the neural responses to continuous speech change across the adult lifespan for both acoustic and linguistic speech processing. These are most likely explained by compensation mechanisms that occur during healthy aging. Traces of this compensation mechanism are reported as modifications in the neural response to acoustic and linguistic speech characteristics in terms of spatial and temporal differences, suggesting structural and functional changes. Additionally, different frontal patterns were observed for linguistic processing, suggesting that older adults recruit additional frontal brain regions to compensate for the age-related decline.
Highlights
With increasing age, linguistic neural tracking of speech decreases.
With increasing age, the processing speed of linguistic aspects of speech slows down.
The processing speed for word-level linguistics is likely affected by cognition.
Older adults rely on compensation mechanisms during speech processing.
The compensation mechanism affects spatial and temporal aspects of neural responses.
... And it is the frontal region that is closely related to cognitive ability. Damage to this region will lead to impairment of cognition, extraction of vocabulary, and other functions (Wierenga et al., 2008;Wang et al., 2010;Goh et al., 2013). ...
Brain health is an important research direction of neuroscience. In addition to the effects of diseases, we cannot ignore the negative effect of aging on brain health. There have been many studies on brain aging, but only a few have used dynamic models to analyze differences in micro brain characteristics in healthy people. In this article, we use the relaxed mean-field model (rMFM) to study the effects of normal aging. Two main parameters of this model are the recurrent connection strength and subcortical input strength. The sensitivity of the rMFM to the initial values of the parameters has not been fully discussed in previous research. We examine this issue through repeated numerical experiments and obtain a reasonable initial parameter range for this model. Differences in recurrent connection strength and subcortical input strength due to aging have also not been studied previously. We use statistical methods to find the regions of interest (ROIs) exhibiting significant differences between young and old groups. Further, we carry out a difference analysis on the process of change of these ROIs on a more detailed timescale. We find that even with the same final results, the trends of change in these ROIs are different. This shows that to develop possible methods to prevent or delay brain damage due to aging, more attention needs to be paid to the trends of change of different ROIs, not just the final results.
... Some studies showed that increased frontal FC was associated with better cognitive performance in cognitively normal older adults, suggesting a compensatory neural process. [45][46][47] According to the famous model named the "scaffolding theory of aging and cognition (STAC)", with the neuronal declines, compensatory scaffolding, i.e., compensatory recruitment or reallocation of cognitive resources, could be induced to maintain cognitive function and life-course factors (including CR) could regulate the process. 48,49 However, other studies showed that increased frontal FC was associated with worse cognitive performance in healthy elderly or subjects with mild cognitive impairment, 50,51 suggesting that the increased FC might reflect pathology-or age-related dedifferentiation of brain activities and could be harmful. ...
Aims
This study aimed to analyze the potential association between cognition reserve (CR) components, including education, working activity, and leisure time activity, and cognitive function in subjects with white matter hyperintensities (WMH). The study also explored the role of the frontoparietal control network (FPCN) in such association.
Methods
White matter hyperintensities subjects with and without cognitive impairment (CI) were evaluated with multimodal magnetic resonance imaging, neuropsychological testing, and CR survey. FPCN patterns were assessed with dorsolateral prefrontal cortex seed‐based functional connectivity analysis.
Results
Education was positively associated with cognitive function in WMH subjects with or without CI, whereas working activity and leisure time activity were positively associated with cognitive function only in those without CI. Similarly, education was associated with bilateral FPCN in both WMH groups, whereas working activity and leisure time activity were associated with bilateral FPCN mainly in the group without CI. Furthermore, FPCN partially mediated the association between education and cognitive function in both WMH groups.
Conclusion
Education showed a positive impact on cognitive function in WMH subjects regardless of their cognitive status, whereas working activity and leisure time activity exhibited beneficial effects only in those without CI. The FPCN mediated the beneficial effect of education on cognitive function.
... Neuroimaging studies have indicated that hemispheric specialization lessens with advancing age: this happens due to the recruitment of additional cortical areas in order to preserve performance, which leads to relative increases in bilateral activation (Cabeza, 2002;Reuter-Lorenz et al., 2000). This effect has been reported with language functions such as fluency and naming (La et al., 2016;Meinzer et al., 2012;Wierenga et al., 2008), but also with other functions such as the motor system and the ventral visual system (Carp et al., 2011;Park et al., 2004). Second, the right-hemispheric involvement in semantic fluency might to some degree be the result of applying visual imaging strategies while performing fluency tasks (Biesbroek, van Zandvoort, et al., 2016;Gordon et al., 2018). ...
Aging is associated with an increased risk for developing vascular pathology in cerebral white matter (WM). These brain changes can have a variety of cognitive repercussions, ranging from insignificant to mild cognitive impairment to dementia. Concomitant WM pathology is also frequently found in patients with mild cognitive impairment (MCI) and Alzheimer’s disease (AD). Previous research generally supports the notion that WM pathology and AD-related pathology would have a cumulative impairing effect on cognition, but relatively few studies have focused on studying these effects. Thus, the aim of this thesis was to investigate the effects of WM pathology on cognitive function in cognitively healthy older adults and patients with MCI or AD.
Study I investigated the effects of WM pathology on general cognitive functioning as measured by the CERAD-NB and utilized visual ratings of magnetic resonance imaging (MRI) data. Here, AD patients with severe frontal WM pathology had markedly lower performances than AD patients with milder pathology.
Study II utilized the same sample as Study I but expanded the scope of analysis to include four specific cognitive domains. Frontal WM pathology was associated with lower cognitive performance in processing speed and visual memory, and parieto-occipital WM pathology solely with processing speed, in all groups. Furthermore, notably slower processing speed performance was seen in AD patients with moderate or severe left frontal WM pathology than in AD patients with less cerebrovascular pathology in that region.
Study III included the same four cognitive domains as Study II but utilized quantitative volumetric measurements of WM pathology. A portion of the sample used in Study II had to be excluded due to inadequate MRI resolution, which resulted in combining the MCI and AD groups into a single patient group. Overall, temporal and parieto-occital WM pathology were associated with lower processing speed, and parieto-occipital WM pathology with lower verbal memory. Furthermore, a group-specific effect was seen in the follow-up analyses: Here WM pathology in the left temporal lobe was associated with lower processing speed only in MCI or AD patients.
Study IV utilized the same sample and image analysis methods as Study III but focused solely on verbal fluency. Here, WM pathology in bilateral frontal, bilateral parieto-occipital and right temporal areas was associated with semantic fluency in right-handed participants. However, no cumulative effects on verbal fluency impairment were seen specifically in patients with MCI or AD.
The results of this thesis support the notion that WM pathology and AD-related pathologies can have cumulative effects on cognition. More specifically, AD patients who have major levels of WM pathology especially in frontal cerebral areas are likely to exhibit more cognitive impairments when compared to patients with milder levels of WM pathology. Impairments may show up as slowed information processing speed and lowered general cognitive functioning, which can be detected with general-level cognitive measures such as the Total Score of the CERAD-NB. As previous studies have shown that the prevalence of WM pathology can be lowered by minimizing modifiable risk factors and fostering physical and cognitive activity, the pre-emptive targeting of these factors is likely to yield long-term benefits in maintaining cognition in MCI and AD.
... Hence, Crosson (2021) reasoned that while corticocortical processes rapidly and iteratively convert a semantic concept to a word choice, cortico-thalamo-cortical circuits maintain a semantic representation that can be compared to choices made at each step of retrieving the best lexical representation to ensure that the lexical decisions are associated with the semantic concept. In one of our picture-naming studies (Wierenga et al., 2008), it took younger participants (20-34 years old) an average of 1,400+ ms from first presentation of the picture to speaking the word representing the object in the picture, and it took older participants (68-84 years old) an average of 1,600+ ms to do the same. This amount of time would not be necessary for a simple linear transmission of information from one cortical processor to the next, since such transmission can occur on the order of milliseconds. ...
Typically, thalamic aphasias appear to be primarily lexical-semantic disorders representing difficulty using stored declarative memories for semantic information to access lexical word forms. Yet, there also is reason to believe that the thalamus might play a role in linguistic procedural memory. For more than two decades, we have known that basal ganglia dysfunction is associated with difficulties in procedural learning, and specific thalamic nuclei are the final waypoint back to the cortex in cortico-basal ganglia-cortical loops. Recent analyses of the role of the thalamus in lexical-semantic processes and of the role of the basal ganglia in linguistic processes suggest that thalamic participation is not simply a matter of declarative vs. procedural memory, but a matter of how the thalamus participates in lexical-semantic processes and in linguistic procedural memory, as well as the interaction of these processes. One role for the thalamus in accessing lexical forms for semantic concepts relates to the stabilization of a very complex semantic-lexical interface with thousands of representations on both sides of the interface. Further, the possibility is discussed that the thalamus, through its participation in basal ganglia loops, participates in two linguistic procedural memory processes: syntactic/grammatical procedures and procedures for finding words to represent semantic concepts, with the latter interacting intricately with declarative memories. These concepts are discussed in detail along with complexities that can be addressed by future research.
... Not surprisingly, ageing negatively affects many aspects of cognition, as demonstrated by a large body of work indicating that older adults show worse performance than younger adults in a variety of cognitive tasks. For example, older adults consistently display lower accuracy and/or slower performance in tasks measuring episodic memory 1-3 , word recognition and retrieval 4,5 , word learning 6,7 , implicit learning of complex skills and sequences [8][9][10] , and various visuo-spatial abilities 11,12 . Though some of these age differences may be due to age-related decreases in overall processing speed or other general factors [13][14][15] , reductions in many cognitive functions are still detectable even when controlling for such variables [16][17][18][19] and thus seem to represent specific neurocognitive declines 1,20 . ...
Many but not all cognitive abilities decline during ageing. Some even improve due to lifelong experience. The critical capacities of attention and executive functions have been widely posited to decline. However, these capacities are composed of multiple components, so multifaceted ageing outcomes might be expected. Indeed, prior findings suggest that whereas certain attention/executive functions clearly decline, others do not, with hints that some might even improve. We tested ageing effects on the alerting, orienting and executive (inhibitory) networks posited by Posner and Petersen’s influential theory of attention, in a cross-sectional study of a large sample (N = 702) of participants aged 58–98. Linear and nonlinear analyses revealed that whereas the efficiency of the alerting network decreased with age, orienting and executive inhibitory efficiency increased, at least until the mid-to-late 70s. Sensitivity analyses indicated that the patterns were robust. The results suggest variability in age-related changes across attention/executive functions, with some declining while others improve.
... Another challenge that commonly presents itself in this context is age. Older adults consistently experience difficulties in word retrieval, which may invoke compensatory mechanisms during task performance [33,34]. This phenomenon may result in the engagement of cortical regions not generally involved in language processing, resulting in misleading lateralization evaluation. ...
Objectives
Crossed cerebro-cerebellar BOLD activations have recently come to light as additional diagnostic features for patients with brain tumors. The covert verb generation (VG) task is a widely used language paradigm to determine these language-related crossed activations. Here we demonstrate these crossed activations in two additional language paradigms, the semantic and phonological association tasks. We propose the merit of these tasks to language lateralization determination in the clinic as they are easy to monitor and suitable for patients with aphasia.Methods
Patients with brain tumors localized at different cortical sites (n = 71) performed three language paradigms, namely the VG task as well as the semantic (SA) and phonological (PA) association tasks with button-press responses. Respective language activations in disparate cortical regions and the cerebellum were assigned laterality. Agreements in laterality between the two new tasks and the verb generation task were tested using Cohen’s kappa.ResultsBoth tasks significantly agreed in cortical and cerebellar lateralization with the verb generation task in patients. Additionally, a McNemar test confirmed the presence of crossed activations in the cortex and the cerebellum in the entire subject population.Conclusion
We demonstrated that the semantic and phonological association tasks resulted in crossed cerebro-cerebellar language lateralization activations as those observed due to the covert verb generation task. This may suggest the possibility of these tasks being used conjointly with the traditional verb generation task, especially for subjects that may be unable to perform the latter.Key Points• The semantic and phonological association tasks can be useful as additional presurgical fMRI language lateralization paradigms for brain tumor patients along with the standard verb generation task.• All three tasks also confirm the presence of crossed cerebro-cerebellar language activations in the current subject population.
... As mentioned above, other non-linguistic or domaingeneral mechanisms can explain lexical production difficulties in older adults, typically a decline in executive functions [76,81,204], together with reduced processing speed or not [156]. The processing speed theory attributes cognitive decline to a decrease in information LS-lifespan LS-reserve processing speed, which results in operations prevented from being successfully executed or chained due to limited time [155]. ...
In the absence of any neuropsychiatric condition, older adults may show declining performance in several cognitive processes and among them, in retrieving and producing words, reflected in slower responses and even reduced accuracy compared to younger adults. To overcome this difficulty, healthy older adults implement compensatory strategies, which are the focus of this paper. We provide a review of mainstream findings on deficient mechanisms and possible neurocognitive strategies used by older adults to overcome the deleterious effects of age on lexical production. Moreover, we present findings on genetic and lifestyle factors that might either be protective or risk factors of cognitive impairment in advanced age. We propose that “aging modulating factors” (AMF) can be modified, offering
prevention opportunities against aging effects. Based on our review and this proposition, we introduce an integrative neurocognitive model of mechanisms and compensatory strategies for lexical production in older adults (entitled Lexical Access and Retrieval in Aging, LARA). The main hypothesis defended in LARA is that cognitive aging evolves heterogeneously and involves complementary domain-general and domain-specific mechanisms, with substantial inter-individual variability, reflected at behavioral, cognitive, and brain levels. Furthermore, we argue that the ability to compensate for the effect of cognitive aging depends on the amount of reserve specific to each individual which is, in turn, modulated by the AMF. Our conclusion is that a variety of mechanisms and compensatory strategies coexist in the same individual to oppose the effect of age. The role of reserve is pivotal for a successful coping with age-related changes and future research should continue to explore the modulating role of AMF.
... It is also important to note that the degree of lateralization most likely depends on age, as functional neuroimaging studies on older participant have indicated a general reduction in hemispheric specialization in favor of more bilateral activation (Reuter-Lorenz et al., 2000;Cabeza, 2002). This age-related restructuring of the neural architecture has been posited to occur primarily by recruiting additional cortical areas to preserve performance and has been documented not only in VF tasks (Meinzer et al., 2012;La et al., 2016) and overt naming (Wierenga et al., 2008) but also in other cognitive functions such as the ventral visual system (Park et al., 2004) and the motor system (Carp et al., 2011). Furthermore, some investigators have speculated that the involvement of the right hemisphere in semantic fluency tasks may reflect the utilization of visuospatial mental imaging strategies for these tasks (Biesbroek et al., 2016;Gordon et al., 2018). ...
Background: White matter hyperintensities (WMHs) are markers for cerebrovascular pathology, which are frequently seen in patients with mild cognitive impairment (MCI) and Alzheimer’s disease (AD). Verbal fluency is often impaired especially in AD, but little research has been conducted concerning the specific effects of WMH on verbal fluency in MCI and AD.
Objective: Our aim was to examine the relationship between WMH and verbal fluency in healthy old age and pathological aging (MCI/AD) using quantified MRI data.
Methods: Measures for semantic and phonemic fluency as well as quantified MRI imaging data from a sample of 42 cognitively healthy older adults and 44 patients with MCI/AD (total n = 86) were utilized. Analyses were performed both using the total sample that contained seven left-handed/ambidextrous participants, as well with a sample containing only right-handed participants (n = 79) in order to guard against possible confounding effects regarding language lateralization.
Results: After controlling for age and education and adjusting for multiple correction, WMH in the bilateral frontal and parieto-occipital areas as well as the right temporal area were associated with semantic fluency in cognitively healthy and MCI/AD patients but only in the models containing solely right-handed participants.
Conclusion: The results indicate that white matter pathology in both frontal and parieto-occipital cerebral areas may have associations with impaired semantic fluency in right-handed older adults. However, elevated levels of WMH do not seem to be associated with cumulative effects on verbal fluency impairment in patients with MCI or AD. Further studies on the subject are needed.
... A great deal of evidence supports the hypothesis that the frontal cortex coordinates the transfer of various perceptual information from contextual cues and executes corresponding behavioral responses to achieve specific goals, which is known as the perception-action cycle (Fuster, 2001;Miller and Cohen, 2001). While many studies found that fMRI activity in the frontal cortex was associated with multiple cognitive performances (Wierenga et al., 2008;Obler et al., 2010;Gu et al., 2019;Liu R. et al., 2019), the present study extended these associations to regional vasodilatory activity and cognitive performance, i.e., the CVR in the frontal regions was significantly associated with executive function, visuospatial function, and language. Thus, not only the brain activity but also the vasodilatory activity in the frontal regions could reflect the development of CI in hypertensive patients. ...
Mechanisms underlying cognitive impairment (CI) in hypertensive patients remain relatively unclear. The present study aimed to explore the relationship among serum exosomal microRNAs (miRNAs), cerebrovascular reactivity (CVR), and cognitive function in hypertensive patients. Seventy-three hypertensive patients with CI (HT-CI), 67 hypertensive patients with normal cognition (HT-NC), and 37 healthy controls underwent identification of exosomal miRNA, multimodal magnetic resonance imaging (MRI) scans, and neuropsychological tests. CVR mapping was investigated based on resting-state functional MRI data. Compared with healthy subjects and HT-NC subjects, HT-CI subjects displayed decreased serum exosomal miRNA-330-3p. The group difference of CVR was mainly found in the left frontal lobe and demonstrated that HT-CI group had a lower CVR than both HT-NC group and control group. Furthermore, both the CVR in the left medial superior frontal gyrus and the miRNA-330-3p level were significantly correlated with executive function (r = −0.275, P = 0.021, and r = −0.246, P = 0.04, respectively) in HT-CI subjects, and the CVR was significantly correlated with the miRNA-330-3p level (r = 0.246, P = 0.040). Notably, path analysis showed that the CVR mediated the association between miRNA-330-3p and executive function. In conclusion, decreased miRNA-330-3p might contribute to CI in hypertensive patients by decreasing frontal CVR and could be a biomarker of early diagnosis.
... Indeed, accuracy in vocabulary measures is generally maintained or even increased until at least 65 years of age (Salthouse, 2014), as the relationship between age and semantic knowledge degradation follows a quadratic function (Catricalà et al., 2015). Naming accuracy thus appears to be a long preserved ability despite an increase in response time (Wierenga et al., 2008) and a complaint regarding the retrieval of proper names (Condret-Santi et al., 2013), which may be associated with a general slowing down in information processing (Feyereisen et al., 1998). Yet, the naming of common names is not a frequent complaint in healthy aging or when impaired, it may be an early sign of a pathological process (Bowles et al., 1987;Jacobs et al., 1995). ...
Aging is a lifelong process that starts at birth. Throughout the course of their life, individuals are exposed to various levels of stimulating activities. A higher level of engagement in such activities is suspected to protect against the normal course of cognitive aging or the cognitive manifestations of age-related brain diseases. However, the exact mechanism underlying such protective action remains unclear. The concept of the neurocognitive reserve was introduced to refer to the hypothesis that engagement in stimulating activities shapes brain structure and function, thus indirectly allowing for better preserved cognitive abilities. Although it is known that word production is among the best-preserved cognitive abilities in aging, the underlying neurofunctional mechanisms that allow this relative preservation are still unknown, and it is still unclear how engagement in stimulating activities affects these processes. The objective of this study is to describe the brain functional connectivity patterns associated with picture-naming abilities in younger and older adults with varying levels of engagement in stimulating activities, as a proxy for neurocognitive reserve. A mediation analysis was applied to determine whether the association between reserve proxies and naming accuracy is dependent on task FC. Results show that naming accuracy depends on the posterior cingulate cortex (PCC) functional decoupling in both younger and older adults but through different pathways. While high-performing older adults rely on the asynchronization of this area from motor speech regions' activity, the best-performing younger adults rely on the functional decoupling with language-related regions. Mediation analysis reveals that the PCC decoupling mediates the relationship between the level of engagement in stimulating activities and naming accuracy in younger adults, but not in older adults. These findings suggest that reserve-related mechanisms may be more critical for naming in early adult life, while older adults' neurofunctional organization may benefit more from a lifetime of acquired knowledge.
... z-transformed to the original 52-item accuracy distribution for healthy older American adults reported byWierenga et al. (2008) (see method); "PPT-s Pics" = picture version of the PPT unvalidated short form; "Trail Making Test-Form A" (maximum time is 150 s), Trails-B = Trail Making Test-Form B (maximum time is 300 s), scores rounded to the nearest second(Tombaugh, 2004;Weintraub et al., 2009). "NC" denotes that a participant did not complete the task within the allotted time.^indicates that the raw score exceeded worse than two standard deviations below the mean(s) reported for healthy controls. ...
The dynamic and unpredictable nature of expressive vocabulary dropout in progressive anomia presents a challenge for language intervention. We evaluated whether eye gaze patterns during naming could predict anomia for the same items in the near future. We tracked naming accuracy and gaze patterns as patients with semantic (n = 7) or logopenic (n = 2) variants of Primary Progressive Aphasia or amnestic Alzheimer’s Disease (n = 1), named photographs of people and objects. Patients were tested three or more times spaced roughly evenly over an average duration of 19.1 months. Target words named accurately at baseline were retrospectively coded as either known (i.e., consistently named) or vulnerable (i.e., inaccurately or inconsistently named) based on naming accuracy over the study interval. We extracted gaze data corresponding to successful naming attempts and implemented logistic mixed effects models to determine whether common gaze measures could predict each word’s naming status as known or vulnerable. More visual fixations and greater visual fixation dispersion predicted later anomia. These findings suggest that eye tracking may yield a biomarker of the robustness of particular target words to future expressive vocabulary dropout. We discuss the potential utility of this finding for optimizing treatment for progressive anomia.
... This is a departure from earlier findings that have largely implicated left hemisphere structures (Badre et al. 2005;Nagel et al. 2008;Snyder et al. 2011;Souza et al. 2009) however it is possible that the bilateral activity noted in our cohort and Noonan et al.'s cohort relate to the older age of these participants relative to previously studied cohorts and reflect typical age-related hemispheric compensation (Berlingeri et al. 2013;Cabeza 2002). Indeed, this phenomenon has been specifically reported in studies of age-related changes in semantic processes (Diaz et al. 2014;Wierenga et al. 2008). ...
A small number of studies have described verbal selection deficits in Parkinson’s disease (PD) when selection must occur among competing alternatives. However, these studies have largely focused on single-word processing, or have utilised sentence stems that carry high contextual constraint, thus reducing selection demands. The present study aimed to determine the influence of variable contextual constraint on the selection of a verbal response in PD. This was achieved using an adaption of the Hayling Sentence Completion Task whereby PD participants and matched controls were required to provide a single word to complete a cloze probability sentence stem that carried a low, medium, or high degree of contextual constraint. Results revealed no main effect of group in terms of response time or accuracy, though a group-by-condition interaction in accuracy was noted. This was characterised by a significant difference in accuracy between low and medium levels of constraint for control participants, but no significant difference for the PD group. Functional MRI data revealed marked between-group differences in underlying neural activity. The control group showed increased recruitment of the dorsal striatum and the vlPFC under conditions that placed greater demands upon selection (i.e. low and medium constraint), and greater activity overall in the left dlPFC and right vlPFC. However, in the PD group, behavioural performance appeared to be maintained despite underlying decreases in frontostriatal activity, suggesting other compensatory mechanisms that may include changes in functional connectivity or an over-medication effect in frontal networks in response to loss of signalling in cortico-subcortical pathways.
... Moreover, the results of a stronger functional connectivity of right FPCN with left IFG (a core region of left FPCN) and a stronger bilateral synchronisation of FPCN in near-centenarians and centenarians without dementia, were also in line with prior findings of an increased bilateral frontal activation in response to episodic memory retrieval tasks in high-performing older individuals (Cabeza et al., 2018;Wierenga et al., 2008). Specifically, while young adults and low-performing older adults showed unilateral frontal activity, high-performing older adults tended to recruit bilateral frontal regions for the task, suggesting a compensatory reorganisation of functional network in older adults with better reserve of cognition . ...
Centenarians without dementia can be considered as a model of successful ageing and resistance against age-related cognitive decline. Is there something special about their brain functional connectivity that helps them preserve cognitive function into the 11th decade of life? In a cohort of 57 dementia-free near-centenarians and centenarians (95-103 years old) and 66 cognitively unimpaired younger participants (76-79 years old), we aimed to investigate brain functional characteristics in the extreme age range using resting-state functional MRI. Using group-level independent component analysis and dual regression, results showed group differences in the functional connectivity of seven group-level independent component (IC) templates, after accounting for sex, education years, and grey matter volume, and correcting for multiple testing at family-wise error rate of 0.05. After Bonferroni correction for testing 30 IC templates, near-centenarians and centenarians showed stronger functional connectivity between right frontoparietal control network (FPCN) and left inferior frontal gyrus (Bonferroni-corrected p = 0.024), a core region of the left FPCN. The investigation of between-IC functional connectivity confirmed the voxel-wise result by showing stronger functional connectivity between bilateral FPCNs in near-centenarians and centenarians compared to young-old controls. In addition, near-centenarians and centenarians had weaker functional connectivity between default mode network and fronto-temporo-parietal network compared to young-old controls. In near-centenarians and centenarians, stronger functional connectivity between bilateral FPCNs was associated with better cognitive performance in the visuospatial domain. The current study highlights the key role of bilateral FPCN connectivity in the reserve capacity against age-related cognitive decline.
... To examine this, we correlated whole-brain functional connectivity using the language seed regions with a task involving both language processing and executive function-the Stroop task-to better understand the relationship between language and executive function regions, and to examine how RSFC may predict age-related differences in behavioral performance. Because prior research has found that increased task-based functional activation in right hemisphere regions was associated with improved word retrieval performance in older adults (e.g., Wierenga et al., 2008), and others have observed increased age-related functional connectivity between left frontal and bilateral parietal regions, we predicted that in older adults, stronger functional connectivity between our seed language regions and right hemisphere regions involved in executive function would correlate with better Stroop performance. Moreover, given well-documented age-related decline in the frontal cortex, age-related differences in RSFC and RSFCbehavior relations may be greatest in frontal regions. ...
Healthy older adults commonly report increased difficulties with language production. This could reflect decline in the language network, or age-related declines in other cognitive abilities that support language production, such as executive function. To examine this possibility, we conducted a whole-brain resting-state functional connectivity (RSFC) analysis in older and younger adults using two seed regions—the left posterior superior temporal gyrus and left inferior frontal gyrus. Whole-brain connectivities were then correlated with Stroop task performance to investigate the relationship between RSFC and executive function. We found that overall, younger adults had stronger RSFC than older adults. Moreover, in older, but not younger, adults stronger RSFC between left IFG and right hemisphere executive function regions correlated with better Stroop performance. This suggests that stronger RSFC among older adults between left IFG and right hemisphere regions may serve a compensatory function.
... For example, Birn et al. (2010) reported that an automatic speech task (i.e., citing months of the year) yielded increased activity of RH supramarginal gyrus in healthy young adults compared to semantic and phonemic fluency activation patterns. The active involvement of RH supramarginal gyrus, however, has been found in other previous studies of verbal fluency or object naming in older adults and individuals with dementia (Wierenga et al., 2008;Marsolais et al., 2015). Furthermore, Meinzer et al. (2012) found that compared to cognitively healthy older adults, RH supramarginal gyrus showed negative activity in healthy young adults during an externally paced verbal fluency paradigm. ...
Currently there are ~6 million Americans who are affected by dementia. Verbal fluency tasks have been commonly and frequently utilized to document the disease progression in many forms of dementia. Verb fluency has been found to display substantial potential to detect and monitor the cognitive declines of individuals with dementia who have fronto-striatal involvement. The neural substrates underlying verb fluency task performance, however, have remained unclear so far, especially in individuals with dementia. Therefore, in the current study, brain activation patterns of seven individuals with dementia and nine healthy older adults were investigated using functional MRI. The participants performed in the scanner an overt, subject-paced verb fluency task, representative of fluency tasks used in clinical settings. The brain activation patterns during the verb fluency task were compared between the two groups, and a correlational analysis was conducted to determine the neural correlates of verb fluency performance. The results suggest that compared to healthy older adults, individuals with dementia demonstrated poorer verb fluency performance and showed higher activation in specific neural regions, such as the bilateral frontal lobe. In addition, the correlational analysis revealed that poorer verb fluency performance lead to increased activation in certain cortical and subcortical areas, including left hippocampus and right supramarginal gyrus. The current findings are consistent with previous neurophysiological findings related to semantic (noun) fluency performance in older adults and individuals with dementia and add to the empirical evidence that supports the role of the frontal lobe and hippocampus in verb retrieval and search. Declines in verb fluency performance cannot only be used as a cognitive marker, but also represent neuropathological changes due to the neurodegenerative disease.
Cognitive decline is one of the most distinct signs of aging, and age-related cognitive decline is a heterogeneous issue varying in different cognitive domains and has significant differences among older adults. Identifying characteristics of cognitive aging is the basis of cognitive disease for early-detection and healthy aging promotion. In the current chapter, age-related decline of main cognitive domains, including sensory perception, memory, attention, executive function, language, reasoning, and space navigation ability are introduced respectively. From these aspects of cognition, we focus on the age-related effects, age-related cognitive diseases, and possible mechanisms of cognitive aging.
In the human brain, functionally and anatomically defined systems exist for encoding, consolidating, and retrieving memories of experiences (episodic memory); accumulating and accessing factual information in a body of knowledge (semantic memory); and actively processing and manipulating information (working memory). These three memory systems can be distinguished behaviorally and neurobiologically from other nondeclarative memory systems such as procedural learning and priming [1–4]. Brain-behavior studies using a variety of approaches from lesion-based research to functional MRI (fMRI) demonstrate distinct though highly interrelated neural circuitry for episodic, semantic, and working memory [3, 5]. Each of these memory systems, despite their close interaction, is affected somewhat differently by aging and dementia.KeywordsEpisodic memorySemantic memoryWorking memoryAlzheimer’s diseaseAgingMild cognitive impairmentSubjective cognitive declinefMRIFunctional connectivityBiomarkers
Background:
The apolipoprotein E (APOE) ɛ4 allele confers risk for age and Alzheimer's disease related cognitive decline but the mechanistic link remains poorly understood. Blood oxygenation level dependent (BOLD) response in the fusiform gyrus (FG) during object naming appears greater among APOEɛ4 carriers even in the face of equivalent cognitive performance, suggesting neural compensation. However, BOLD is susceptible to known age and APOE-related vascular changes that could confound its interpretation.
Objective:
To address this limitation, we used calibrated fMRI during an object naming task and a hypercapnic challenge to obtain a more direct measure of neural function - percent change cerebral metabolic rate of oxygen consumption (%ΔCMRO2).
Methods:
Participants were 45 older adults without dementia (28 ɛ4- , 17 ɛ4+) between the ages of 65 and 85. We examined APOE-related differences in %ΔCMRO2 in the FG during object naming and the extent to which APOE modified associations between FG %ΔCMRO2 and object naming accuracy. Exploratory analyses also tested the hypothesis that %ΔCMRO2 is less susceptible to vascular compromise than are measures of %ΔCBF and %ΔBOLD.
Results:
We observed a modifying role of APOE on associations between FG %ΔCMRO2 and cognition, with ɛ4 carriers (but not non-carriers) demonstrating a positive association between right FG %ΔCMRO2 and object naming accuracy.
Conclusion:
Results suggest that the relationship between neural function and cognition is altered among older adult APOEɛ4 carriers prior to the onset of dementia, implicating CMRO2 response as a potential mechanism to support cognition in APOE-related AD risk.
There is considerable debate about whether additional fMRI-measured activity in the right prefrontal cortex readily observed in older adults represents compensatory activation that enhances cognition or whether maintenance of youthful brain activity best supports cognitive function in late adulthood. To investigate this issue, we tested a large lifespan sample of 461 adults (aged 20-89) and treated degree of left-lateralization in ventrolateral and dorsolateral prefrontal cortex during a semantic judgment fMRI task as an individual differences variable to predict cognition. We found that younger adults were highly left-lateralized, but lateralization did not predict better cognition, whereas higher left-lateralization of prefrontal cortex predicted better cognitive performance in middle-aged adults, providing evidence that left-lateralized, youth-like patterns are optimal in middle age. This relationship was reversed in older adults, with lower laterality scores associated with better cognition. The findings suggest that bilaterality in older adults facilitates cognition, but early manifestation of this pattern during middle age is characteristic of low performers. Implications of these findings for current theories of neurocognitive aging are discussed.
Procrastination refers to an irrationally delay for intended courses of action despite of anticipating a negative consequence due to this delay. Previous studies tried to reveal the neural substrates of procrastination in terms of connectome-based biomarkers. Based on this, we proposed a unified triple brain network model for procrastination and pinpointed out what challenges we are facing in understanding neural mechanism of procrastination. Specifically, based on neuroanatomical features, the unified triple brain network model proposed that connectome-based underpinning of procrastination could be ascribed to the abnormalities of self-control network (i.e., dorsolateral prefrontal cortex, DLPFC), emotion-regulation network (i.e., orbital frontal cortex, OFC), and episodic prospection network (i.e., para-hippocampus cortex, PHC). Moreover, based on the brain functional features, procrastination had been attributed to disruptive neural circuits on FPN (frontoparietal network)-SCN (subcortical network) and FPN-SAN (salience network), which led us to hypothesize the crucial roles of interplay between these networks on procrastination in unified triple brain network model. Despite of these findings, poor interpretability and computational model limited further understanding for procrastination from theoretical and neural perspectives. On balance, the current study provided an overview to show current progress on the connectome-based biomarkers for procrastination, and proposed the integrative neurocognitive model of procrastination.
Investigating interhemispheric interactions between homologous cortical regions during language processing is of interest. Despite prevalent left hemisphere lateralization of language, the right hemisphere also plays an important role and interhemispheric connectivity is influenced by language experience and is implicated in second language (L2) acquisition. Regions involved in language processing have differential connectivity to other cortical regions and to each other, and play specific roles in language. We examined the interhemispheric interactions of subregions of the inferior frontal gyrus (areas 44 and 45), the adjacent area 9/46v in the middle frontal gyrus, the superior temporal gyrus (STG), and the posterior inferior parietal lobule (pIPL) in relation to distinct and specific aspects of L2 learning success. The results indicated that the connectivity between left and right areas 44 and 9/46v predicted improvement in sentence repetition, connectivity between left and right area 45 and mid-STG predicted improvement in auditory comprehension, and connectivity between left and right pIPL predicted improvement in reading speed. We show interhemispheric interactions in the specific context of facilitating performance in adult L2 acquisition that follow an anterior to posterior gradient in the brain, and are consistent with the respective roles of these regions in language processing.
Objective:
Language abilities in adulthood remain relatively intact with increasing age, while spatial abilities decline. However, much less is known about ageing effects on spatial language (the ability to verbally describe where objects are located in relation to other objects). The primary goal of this study was to examine age-related changes in naming static and dynamic spatial relations across the adult lifespan. Moreover, we examined whether spatial naming is more closely associated with (non-spatial) verbal or (non-linguistic) visuospatial abilities.
Method:
Healthy adults aged between 18 and 85 years completed a newly developed Spatial Naming Test (SNT), as well as standard object and action naming tests and various visuospatial tasks. The psychometric properties of the novel SNT (inter-rater and test-retest reliability and convergent, divergent, and construct validity) were also examined.
Results:
The psychometric evaluation confirmed the reliability and validity of the SNT. Striking effects of ageing on naming of both static and dynamic spatial relations were found, as well as on visuospatial abilities, while object and action naming remained age invariant. Moreover, both (non-spatial) verbal and (non-linguistic) visuospatial abilities predicted static spatial naming, but only visuospatial abilities accounted for significant variance in dynamic spatial naming beyond age.
Conclusions:
These findings provide the first evidence that naming spatial relations declines in ageing as a function of changes in non-linguistic visuospatial abilities, indicating strong connections between linguistic and non-linguistic representations of space. Theoretical and practical implications of these findings are discussed. (PsycInfo Database Record (c) 2022 APA, all rights reserved).
Semantic memory representations are overall well-maintained in aging whereas semantic control is thought to be more affected. To explain this phenomenon, this study aims to test the predictions of the Compensation Related Utilization of Neural Circuits Hypothesis (CRUNCH) focusing on task demands in aging as a possible framework. The CRUNCH effect would manifest itself in semantic tasks through a compensatory increase in neural activation in semantic control network regions but only up to a certain threshold of task demands. This study will compare 40 young (20–35 years old) with 40 older participants (60–75 years old) in a triad-based semantic judgment task performed in an fMRI scanner while manipulating levels of task demands (low vs. high) through semantic distance. In line with the CRUNCH predictions, differences in neurofunctional activation and behavioral performance (accuracy and response times) are expected in young vs. old participants in the low- vs. high-demand conditions manifested in semantic control Regions of Interest.
Purpose
When speakers retrieve words, they do so extremely quickly and accurately—both speed and accuracy of word retrieval are compromised in persons with aphasia (PWA). This study examined the contribution of two domain-general mechanisms: processing speed and cognitive control on word retrieval in PWA.
Method
Three groups of participants, neurologically healthy young and older adults and PWA ( n = 15 in each group), performed processing speed, cognitive control, lexical decision, and word retrieval tasks on a computer. The relationship between word retrieval speed and other tasks was examined for each group.
Results
Both aging and aphasia resulted in slower processing speed but did not affect cognitive control. Word retrieval response time delays in PWA were eliminated when processing speed was accounted for. Word retrieval speed was predicted by individual differences in cognitive control in young and older adults and additionally by processing speed in older adults. In PWA, word retrieval speed was predicted by severity of language deficit and cognitive control.
Conclusions
This study shows that processing speed is compromised in aphasia and could account for their slowed response times. Individual differences in cognitive control predicted word retrieval speed in healthy adults and PWA. These findings highlight the need to include nonlinguistic cognitive mechanisms in future models of word retrieval in healthy adults and word retrieval deficits in aphasia.
Self-efficacy refers to the beliefs that one possesses about his/her ability to achieve specific targets in a certain context. It is one of the important aspects of metacognitive processes. There are emerging evidences that most of the cognitive processes decline with age but the kind of trajectory metacognitive ability, like self-efficacy, follows as a function of age is yet researchable. The present study aimed at assessing how self-efficacy related to one's ability on the cognitive process of verbal fluency changes with age. For this purpose, three groups with 12 participants in each group ie the young adults, middle-aged adults, and old-aged adults were subjected to letter fluency (LF)-flexibility and category fluency (CF)-flexibility tasks. In addition to performing the tasks, the participants of all groups did a pre-task prediction and a post-task judgment of their respective performances. The differences between predictions, judgments, and actual performances of all subjects were subjected to repeated measure ANOVA and post hoc paired T-test for each group. The results obtained revealed that the verbal fluency performance declined with the age. However, the self-efficacy for verbal fluency, measured by predictions and judgments, revealed that as the individuals grow old, they seem to become more aware of their limited performances. These results open the scope of studying metacognitive processes like self-efficacy on larger samples and variety of cognitive processes that may be significant for cognitive communicative assessment and intervention.
Recently, the focus of functional connectivity analysis of human brain has shifted from merely revealing the inter-regional functional correlation over the entire scan duration to capturing the time-varying information of brain networks and characterizing time-resolved reoccurring patterns of connectivity. Many efforts have been invested into developing approaches that can track changes in re-occurring patterns of functional connectivity over time. In this paper, we propose a sparse deep dictionary learning method to characterize the essential differences of reoccurring patterns of time-varying functional connectivity between different age groups. The proposed method combines both the interpretability of sparse dictionary learning and the capability of extracting sparse nonlinear higher-level features in the latent space of sparse deep autoencoder. In other words, it learns a sparse dictionary of the original data by considering the nonlinear representation of the data in the encoder layer based on a sparse deep autoencoder. In this way, the nonlinear structure and higher-level features of the data can be captured by deep dictionary learning. The proposed method is applied to the analysis of the Philadelphia Neurodevelopmental Cohort. It shows that there exist essential differences in the reoccurrence patterns of function connectivity between child and young adult groups. Specially, children have more diffusive functional connectivity patterns while young adults possess more focused functional connectivity patterns, and the brain function transits from undifferentiated systems to specialized neural networks with the growth.
Semantic cognition is central to understanding of language and the world and, unlike many cognitive domains, is thought to show little age-related decline. We investigated age-related differences in the neural basis of this critical cognitive domain by performing an activation likelihood estimation (ALE) meta-analysis of functional neuroimaging studies comparing young and older people. On average, young people outperformed their older counterparts during semantic tasks. Overall, both age groups activated similar left-lateralised regions. However, older adults displayed less activation than young people in some elements of the typical left-hemisphere semantic network, including inferior prefrontal, posterior temporal and inferior parietal cortex. They also showed greater activation in right frontal and parietal regions, particularly those held to be involved in domain-general controlled processing, and principally when they performed more poorly than the young. Thus, semantic processing in later life is associated with a shift from semantic-specific to domain-general neural resources, consistent with the theory of neural dedifferentiation, and a performance-related reduction in prefrontal lateralisation, which may reflect a response to increased task demands.
Language use is shaped by a pressure to communicate efficiently, yet the tendency towards redundancy is said to increase in older age. The longstanding assumption is that saying more than is necessary is inefficient and may be driven by age-related decline in inhibition (i.e. the ability to filter out irrelevant information). However, recent work proposes an alternative account of efficiency: In certain contexts, redundancy facilitates communication (e.g., when the colour or size of an object is perceptually salient and its mention aids the listener’s search). A critical question follows: Are older adults indiscriminately redundant, or do they modulate their use of redundant information to facilitate communication? We tested efficiency and cognitive capacities in 200 adults aged 19–82. Irrespective of age, adults with better attention switching skills were redundant in efficient ways, demonstrating that the pressure to communicate efficiently continues to shape language use later in life.
Functional magnetic resonance imaging (fMRI) was used to compare frontal-lobe activation in younger and older adults during encoding of words into memory. Participants made semantic or nonsemantic judgments about words. Younger adults exhibited greater activation for semantic relative to nonsemantic judgments in several regions, with the largest activation in the left inferior frontal gyrus. Older adults exhibited greater activation for semantic judgments in the same regions, but the extent of activation was reduced in left prefrontal regions. In older adults, there was a significant association between behavioral tests of declarative and working memory and extent of frontal activation. These results suggest that age-associated decreases in memory ability may be due to decreased frontal-lobe contributions to the initial encoding of experience.
The authors first describe experimental results regarding age-related dedifferentiation in elderly person's ability profiles and age-related increases in interindividual and intraindividual variability. A few general conceptual accounts for these empirical findings are presented, along with a short description of an attempt to formally integrate these 2 sets of findings and explanations at a purely descriptive level. The authors then present empirical findings on aging-induced deterioration of neurotransmitter systems and the increase in CNS variability at the biological level. The authors propose a computational approach which varies the responsivity of the processing units and the internal variability of connectionist networks by manipulating the gain parameter of the sigmoid activation function. The authors then report 2 sets of simulations, each involving 3 groups of networks that differ only in the means of the uniform distributions from which values of gain parameters were sampled. The authors then examine the effect of this gain parameter manipulation on the intercorrelations between the networks' performances in 2 task domains. Finally, the authors discuss the limitations of the present formalization and its implications for the study of lifespan cognitive development. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
The supracallosal medial frontal cortex can be divided into three functional domains: a ventral region with connections to the limbic system, an anterior dorsal region with connections to lateral prefrontal systems, and a posterior dorsal region with connections to lateral motor systems. Lesion and functional imaging studies implicate this medial frontal cortex in speech and language generation. The current functional magnetic resonance imaging (fMRI) study of word generation was designed to determine which of these three functional domains was substantially involved by mapping individual subjects' functional activity onto structural images of their left medial frontal cortex. Of 28 neurologically normal right-handed participants, 21 demonstrated a prominent paracingulate sulcus (PCS), which lies in the anterior dorsal region with connections to lateral prefrontal systems. Activity increases for word generation centered in the PCS in 18 of these 21 cases. The posterior dorsal region also demonstrated significant activity in a majority of participants (16/28 cases). Activity rarely extended into the cingulate sulcus (CS) (3/21 cases) when there was a prominent PCS. If there was no prominent PCS, however, activity did extend into the CS (6/7 cases). In no case was activity present on the crest of the cingulate gyrus, which is heavily connected to the limbic system. Thus, current findings suggest that medial frontal activity during word generation reflects cognitive and motor rather than limbic system participation. The current study demonstrates that suitably designed fMRI studies can be used to determine the functional significance of anatomic variants in human cortex.
This paper examines three methodological issues concerning the measurement of semantic memory impairment in brain-damaged patients. Ten carefully selected patients with dementia of Alzheimer's type (DAT) and anomia were studied. A battery of perceptual tests and direct tests of semantic memory led to the conclusion that these patients represented a homogeneous group having a prominent deterioration of their semantic memory store without visual perceptual deficits.
The first issue addressed in this patient group was whether verbal fluency impairment accurately reflected the loss of semantic memory. It was found that verbal fluency (generation of semantic category lists) was impaired due to two major constraints: deterioration of semantic memory store, and variable difficulties in semantic search. Verbal fluency, therefore, reflects semantic memory loss to some degree, but is not a direct test of semantic memory store in DAT. The second issue was whether semantic memory impairment in our patients conformed to the ‘semantic storage disorder’ syndrome hypothesized by Shallice (1987). It was shown that, consistent with this hypothesis, the patients demonstrated co-occurrence of consistency of errors, loss of semantic cueing, and preserved superordinate knowledge with loss of detailed knowledge of concept items. The third issue was whether semantic cueing and semantic priming, are altered in a similar manner in DAT. It demonstrated that semantic cueing and semantic priming, using the same words whose concepts were degraded in semantic memory, yielded an entirely different pattern of results. Cueing and priming therefore may not be used interchangeably in the study of semantic loss after brain damage.
The purpose of this review is to extend the existing application of the frontal lobe hypothesis of cognitive aging beyond the limited work on inhibitory control (F. N. Dempster, 1992) to include memory processes supported by the prefrontal cortex. To establish a background for this analysis, I review existing models of prefrontal cortex function and present a synthesized model that includes a general function of temporal integration, supported by 4 specific processes: prospective memory, retrospective memory, interference control, and inhibition of prepotent responses. I found the frontal lobe hypothesis to perform well, with the exception of an inability to account for age-related declines in item recall and recognition memory, possibly a result of age-related declines in medial temporal function.
A number of neuroimaging findings have been interpreted as evidence that the left inferior frontal gyrus (IFG) subserves retrieval of semantic knowledge. We provide a fundamentally different interpretation, that it is not retrieval of semantic knowledge per se that is associated with left IFG activity but rather selection of information among competing alternatives from semantic memory. Selection demands were varied across three semantic tasks in a single group of subjects. Functional magnetic resonance imaging signal in overlapping regions of left IFG was dependent on selection demands in all three tasks. In addition, the degree of semantic processing was varied independently of selection demands in one of the tasks. The absence of left IFG activity for this comparison counters the argument that the effects of selection can be attributed solely to variations in degree of semantic retrieval. Our findings suggest that it is selection, not retrieval, of semantic knowledge that drives activity in the left IFG.
This article reviews attempts to characterize the mental operations mediated by left inferior prefrontal cortex, especially the anterior and inferior portion of the gyrus, with the functional neuroimaging techniques of positron emission tomography and functional magnetic resonance imaging. Activations in this region occur during semantic, relative to nonsemantic, tasks for the generation of words to semantic cues or the classification of words or pictures into semantic categories. This activation appears in the right prefrontal cortex of people known to be atypically right-hemisphere dominant for language. In this region, activations are associated with meaningful encoding that leads to superior explicit memory for stimuli and deactivations with implicit semantic memory (repetition priming) for words and pictures. New findings are reported showing that patients with global amnesia show deactivations in the same region associated with repetition priming, that activation in this region reflects selection of a response from among numerous relative to few alternatives, and that activations in a portion of this region are associated specifically with semantic relative to phonological processing. It is hypothesized that activations in left inferior prefrontal cortex reflect a domain-specific semantic working memory capacity that is invoked more for semantic than nonsemantic analyses regardless of stimulus modality, more for initial than for repeated semantic analysis of a word or picture, more when a response must be selected from among many than few legitimate alternatives, and that yields superior later explicit memory for experiences.
Brain imaging and electrophysiological recording studies in humans have reported discrete cortical regions in posterior ventral temporal cortex that respond preferentially to faces, buildings, and letters. These findings suggest a category-specific anatomically segregated modular organization of the object vision pathway. Here we present data from a functional MRI study in which we found three distinct regions of ventral temporal cortex that responded preferentially to faces and two categories of other objects, namely houses and chairs, and had a highly consistent topological arrangement. Although the data could be interpreted as evidence for separate modules, we found that each category also evoked significant responses in the regions that responded maximally to other stimuli. Moreover, each category was associated with its own differential pattern of response across ventral temporal cortex. These results indicate that the representation of an object is not restricted to a region that responds maximally to that object, but rather is distributed across a broader expanse of cortex. We propose that the functional architecture of the ventral visual pathway is not a mosaic of category-specific modules but instead is a continuous representation of information about object form that has a highly consistent and orderly topological arrangement.
The cognitive and neural mechanisms underlying category-specific knowledge remain controversial. Here we report that, across multiple tasks (viewing, delayed match to sample, naming), pictures of animals and tools were associated with highly consistent, category-related patterns of activation in ventral (fusiform gyrus) and lateral (superior and middle temporal gyri) regions of the posterior temporal lobes. In addition, similar patterns of category-related activity occurred when subjects read the names of, and answered questions about, animals and tools. These findings suggest that semantic object information is represented in distributed networks that include sites for storing information about specific object attributes such as form (ventral temporal cortex) and motion (lateral temporal cortex).
The present investigation examined the validity of the revised Hopkins Verbal Learning Test (HVLT-R). In a principal components analysis with varimax rotation, measures of new learning and delayed recall loaded on a single factor distinguishable from measures related to general cognitive function and visual memory. The HVLT-R also correlated most strongly with other tests of verbal memory and relatively weakly with a test of general intelligence. Group comparisons showed that normal controls performed better than age- and education-matched patients with probable Alzheimer's disease (AD) or vascular dementia (VaD). Discriminant function analyses and Bayesian statistics revealed high classification accuracies for dementia patients versus controls. When scores on the HVLT-R and other neuropsychological tests were subjected to discriminant function analyses, performance on the HVLT-R delayed recognition task was found to be the most useful in discriminating patients with AD from those with VaD. We conclude that the HVLT-R is a valid test of verbal learning and memory that is best suited for use with elderly patients suspected of dementia.
Age-related decline in working memory figures prominently in theories of cognitive aging. However, the effects of aging on the neural substrate of working memory are largely unknown. Positron emission tomography (PET) was used to investigate verbal and spatial short-term storage (3 sec) in older and younger adults. Previous investigations with younger subjects performing these same tasks have revealed asymmetries in the lateral organization of verbal and spatial working memory. Using volume of interest (VOI) analyses that specifically compared activation at sites identified with working memory to their homologous twin in the opposite hemisphere, we show pronounced age differences in this organization, particularly in the frontal lobes: In younger adults, activation is predominantly left lateralized for verbal working memory, and right lateralized for spatial working memory, whereas older adults show a global pattern of anterior bilateral activation for both types of memory. Analyses of frontal subregions indicate that several underlying patterns contribute to global bilaterality in older adults: most notably, bilateral activation in areas associated with rehearsal, and paradoxical laterality in dorsolateral prefrontal sites (DLPFC; greater left activation for spatial and greater right activation for verbal). We consider several mechanisms that could account for these age differences including the possibility that bilateral activation reflects recruitment to compensate for neural decline.
Theories of the regulation of cognition suggest a system with two necessary components: one to implement control and another to monitor performance and signal when adjustments in control are needed. Event-related functional magnetic resonance imaging and a task-switching version of the Stroop task were used to examine whether these components of cognitive control have distinct neural bases in the human brain. A double dissociation was found. During task preparation, the left dorsolateral prefrontal cortex (Brodmann's area 9) was more active for color naming than for word reading, consistent with a role in the implementation of control. In contrast, the anterior cingulate cortex (Brodmann's areas 24 and 32) was more active when responding to incongruent stimuli, consistent with a role in performance monitoring.
We used event-related fMRI to investigate age-related differences in PFC activity during separate WM task components (encoding, maintenance, retrieval) with varying memory loads of verbal information. Younger adults showed greater PFC activity than older adults only in dorsolateral PFC, only during memory retrieval. Faster young subjects showed less dorsolateral PFC activation during retrieval than slower young subjects whereas the opposite pattern was observed in older adults. This result was replicated in two additional experiments using verbal and spatial information. Age-related changes in the dorsolateral PFC regions involved in memory retrieval may mediate declines in WM performance. These results suggest a relationship between neural activation and performance that is sigmoid in nature. Age-related differences in performance may be mediated by bias shifts in this sigmoid function.
Declarative memory declines with age, but there is profound variation in the severity of this decline. Healthy elderly adults with high or low memory scores and young adults viewed words under semantic or non-semantic encoding conditions while undergoing fMRI. Young adults had superior memory for the words, and elderly adults with high memory scores had better memory for the words than those with low memory scores. The elderly with high scores had left lateral and medial prefrontal activations for semantic encoding equal to the young, and greater right prefrontal activation than the young. The elderly with low scores had reduced activations in all three regions relative to the elderly with high memory scores. Thus, successful aging was characterized by preserved left prefrontal and enhanced right prefrontal activation that may have provided compensatory encoding resources.
Theories of the regulation of cognition suggest a system with two necessary components: one to implement control and another to monitor performance and signal when adjustments in control are needed. Event-related functional magnetic resonance imaging and a task-switching version of the Stroop task were used to examine whether these components of cognitive control have distinct neural bases in the human brain. A double dissociation was found. During task preparation, the left dorsolateral prefrontal cortex (Brodmann's area 9) was more active for color naming than for word reading, consistent with a role in the implementation of control. In contrast, the anterior cingulate cortex (Brodmann's areas 24 and 32) was more active when responding to incongruent stimuli, consistent with a role in performance monitoring.
Age- (> 55 years) and education-based norms are presented for eight neuropsychological tests: COWAT, BNT, MAE Token, WRAT-R Reading, AMNART, STROOP, TMT, and JLO. These data were obtained via several research projects that are known collectively as Mayo's Older Americans Normative Studies (MOANS). While this normative information should prove useful for each test, the fact that these norms were simultaneously obtained from the same reference group should promote accuracy in the comparison of any person's performance on one test against his or her functioning on any other tests with MOANS norms. Finally, the unique features of this MOANS sample are reviewed. These features must be kept in mind when these norms are applied in any specific clinical or research setting.
Studies of a range of higher cognitive functions consistently activate a region of anterior cingulate cortex (ACC), typically posterior to the genu and superior to the corpus collosum. In particular, this ACC region appears to be active in task situations where there is a need to override a prepotent response tendency, when responding is underdetermined, and when errors are made. We have hypothesized that the function of this ACC region is to monitor for the presence of crosstalk or competition between incompatible responses. In prior work, we provided initial support for this hypothesis, demonstrating ACC activity in the same region both during error trials and during correct trials in task conditions designed to elicit greater response competition. In the present study, we extend our testing of this hypothesis to task situations involving underdetermined responding. Specifically, 14 healthy control subjects performed a verb-generation task during event-related functional magnetic resonance imaging (fMRI), with the on-line acquisition of overt verbal responses. The results demonstrated that the ACC, and only the ACC, was more active in a series of task conditions that elicited competition among alternative responses. These conditions included a greater ACC response to: (1) Nouns categorized as low vs. high constraint (i.e., during a norming study, multiple verbs were produced with equal frequency vs. a single verb that produced much more frequently than any other); (2) the production of verbs that were weak associates, rather than, strong associates of particular nouns; and (3) the production of verbs that were weak associates for nouns categorized as high constraint. We discuss the implication of these results for understanding the role that the ACC plays in human cognition.
Recent studies of blood oxygenation level dependent (BOLD) signal responses averaged over a region of interest have demonstrated that the response is nonlinear with respect to stimulus duration. Specifically, shorter duration stimuli produce signal changes larger than expected from a linear system. The focus of this study is to characterize the spatial heterogeneity of this nonlinear effect. A series of MR images of the visual and motor cortexes were acquired during visual stimulation and finger tapping, respectively, at five different stimulus durations (SD). The nonlinearity was assessed by fitting ideal linear responses to the responses at each SD. This amplitude, which is constant for different SD in a linear system, was normalized by the amplitude of the response to a blocked design, thus describing the amount by which the stimulus is larger than predicted from a linear extrapolation of the response to the long duration stimulus. The amplitude of the BOLD response showed a nonlinear behavior that varied considerably and consistently over space, ranging from almost linear to 10 times larger than a linear prediction at short SD. In the motor cortex different nonlinear behavior was found in the primary and supplementary motor cortexes.
The striatum, which is the major component of the basal ganglia, displays a complex mosaic organization of neurochemical systems that are related to its neuroanatomical connections. This mosaic organization reflects multiple levels of functional compartments. The first level is determined by the segregation of two major striatal output systems, one to the globus pallidus (external segment) and the other to the entopeduncular nucleus and substantia nigra. The second level segregates the cortical outputs of sublaminae of layer V between the patch and matrix compartments of the striatum, which project to the dopaminergic and GABAergic neurons in the substantia nigra, respectively. The third level is related to the topography of cortical inputs by which regions of the striatum may be functionally defined on the basis of the cortical areas with which they are connected. Neurochemical markers display complex mosaic patterns in the striatum that, when examined in the context of the multi-level compartmental organization of the striatum, reveal the highly organized manner by which the striatum processes cortical information.
Numerous theories discuss the neuropsychological functions of the frontal lobes, most based on some concept of supramodality, and an extensive literature presents the phenomenology and semiology of language and communication deficits after focal brain lesions involving the frontal lobes. Despite this, few attempts have been made to link the clinical phenomenology to a theory. This paper presents (1) a general theory of frontal functions; (2) a brief summary of experimental and anatomical literatures in support of defined frontal functional systems; (3) clinical observations that delineate these functional systems for the specific modalities of language and communication; (4) a review of the available literature supporting the idea of specific modal and supramodal language and communication capacities; (5) hypotheses about the distributed anatomy of these functional systems; and (6) implications for traditional clinical notions of aphasia, particularly in relation to a general theory of frontal lobe functions.
No Abstract. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/50393/1/870010102_ftp.pdf
Information about the basal ganglia has accumulated at a prodigious pace over the past decade, necessitating major revisions in the authors' concepts of the structural and functional organization of these nuclei. Recent anatomical and physiological findings have further substantiated the concept of segregated basal ganglia-thalamocortical pathways, and reinforced the general principle that basal ganglia influences are transmitted only to restricted portions of the frontal lobe (even though the striatum receives projections from nearly the entire neocortex). Using the 'motor' circuit as a model, the authors have reexamined the available data on other portions of the basal ganglia-thalamocortical pathways and found that the evidence strongly suggests the existence of at least four additional circuits organized in parallel with the 'motor' circuit. In the discussion that follows, they review some of the anatomic and physiologic features of the 'motor circuit,' as well as the data that support the existence of the other proposed parallel circuits, which they have designated the 'oculomotor,' the 'dorsolateral prefrontal,' the 'lateral orbitofrontal,' and the 'anterior cingulate,' respectively. Each of these five basal ganglia-thalamocortical circuits appears to be centered upon a separate part of the frontal lobe. This list of basal ganglia-thalamocortical circuits is not intended to be exhaustive. In fact, if the conclusions suggested in this review are valid, future investigations might be expected to disclose not only further details (or the need for revisions) of these five circuits, but perhaps also the existence of additional parallel circuits whose identification is currently precluded by a paucity of data.
The 60-item Boston Naming Test was administered to a group of 78 normal, bright, and independently living older adults in five age groupings from 59 to 80+ in an attempt to generate normative data for an older population. Results indicated that naming abilities decline only slightly with advancing age (r = -.33), although consistent with prior research, more variation in performance was found in the higher age groups.
The need for a simply applied quantitative assessment of handedness is discussed and some previous forms reviewed. An inventory of 20 items with a set of instructions and response- and computational-conventions is proposed and the results obtained from a young adult population numbering some 1100 individuals are reported. The separate items are examined from the point of view of sex, cultural and socio-economic factors which might appertain to them and also of their inter-relationship to each other and to the measure computed from them all. Criteria derived from these considerations are then applied to eliminate 10 of the original 20 items and the results recomputed to provide frequency-distribution and cumulative frequency functions and a revised item-analysis. The difference of incidence of handedness between the sexes is discussed.
The Boston Naming Test is commonly viewed as a measure of language ability, particularly, confrontational naming. Its utility in detecting word-retrieval problems in clinical populations is well documented. However, studies which would explore information-processing mechanisms involved in BNT performance are not available. Results of our repeated testing of 122 subjects between the ages of 57 and 85 with the 60-item version of BNT and other measures over three annual probes revealed high stability of the BNT scores over time, which suggests a lack of the practice effect, whereas cross-sectional analysis demonstrated some decline in the BNT scores in subjects over 70 years of age. In spite of the high stability in BNT scores on repeated testing, the pattern of correlations between the BNT and measures tapping different cognitive domains shifted over time. Results suggest predominantly the verbal mode of information processing in BNT performance on the first probe, as opposed to visuo-spatial mode on the third probe in our sample of elderly individuals.
We attempted to characterize the changes in cognition associated with the earliest, or preclinical, stages of Alzheimer's disease (AD) by administering a comprehensive neuropsychological test battery to a group of initially nondemented older adults participating in a prospective epidemiologic study of dementia. Using Cox regression analyses, we examined the associations between baseline neuropsychological test scores and subsequent development of AD. Results confirmed preliminary findings that baseline scores on the Boston Naming Test, Immediate Recall on the Selective Reminding Test, and the Similarities subtest of the Wechsler Adult Intelligence Scale-Revised were significantly and independently associated with later diagnosis of AD. Analyses controlled for the effects of age, education, sex, and language of test administration. These results lend support to the notion of a preclinical phase of AD and indicate that this very early stage of AD is characterized by poor word-finding ability, abstract reasoning, and memory.
A package of computer programs for analysis and visualization of three-dimensional human brain functional magnetic resonance imaging (FMRI) results is described. The software can color overlay neural activation maps onto higher resolution anatomical scans. Slices in each cardinal plane can be viewed simultaneously. Manual placement of markers on anatomical landmarks allows transformation of anatomical and functional scans into stereotaxic (Talairach-Tournoux) coordinates. The techniques for automatically generating transformed functional data sets from manually labeled anatomical data sets are described. Facilities are provided for several types of statistical analyses of multiple 3D functional data sets. The programs are written in ANSI C and Motif 1.2 to run on Unix workstations.
Functional magnetic resonance imaging (FMRI) is a noninvasive technique for mapping regional brain changes in response to sensory, motor, or cognitive activation tasks. Interpretation of these activation experiments may be confounded by more elementary task parameters, such as stimulus presentation or movement rates. We examined the effect of movement rate on the FMRI response recorded from the contralateral primary motor cortex. Four right-handed healthy subjects performed flexion-extension movements of digits 2-5 of the right hand at rates of 1, 2, 3, 4, or 5 Hz. Results of this study indicated a positive linear relationship between movement rate and FMRI signal change. Additionally, the number of voxels demonstrating functional activity increased significantly with faster movement rates. The magnitude of the signal change at each movement rate remained constant over the course of three 8-min scanning series. These findings are similar to those of previous rate studies of the visual and auditory system performed with positron emission tomography (PET) and FMRI.
The basal ganglia comprise several nuclei in the forebrain, diencephalon, and midbrain thought to play a significant role in the control of posture and movement. It is well recognized that people with degenerative diseases of the basal ganglia suffer from rigidly held abnormal body postures, slowing of movement, involuntary movements, or a combination of these a abnormalities. However, it has not been agreed just what the basal ganglia contribute to normal movement. Recent advances in knowledge of the basal ganglia circuitry, activity of basal ganglia neurons during movement, and the effect of basal ganglia lesions have led to a new hypothesis of basal ganglia function. The hypothesis states that the basal ganglia do not generate movements. Instead, when voluntary movement is generated by cerebral cortical and cerebellar mechanisms, the basal ganglia act broadly to inhibit competing motor mechanisms that would otherwise interfere with the desired movement. Simultaneously, inhibition is removed focally from the desired motor mechanisms to allow that movement to proceed. Inability to inhibit competing motor programs results in slow movements, abnormal postures and involuntary muscle activity.
Broca's area, which includes the pars triangularis (PTR) and pars opercularis (POP), is a neuroanatomic region important in speech-language production. Previous data demonstrated that PTR asymmetries are highly correlated with language dominance determined by selective hemispheric anesthesia or Wada testing, suggesting that asymmetries of the PTR may, in part, predict language dominance. The POP, however, has not been measured on volumetric magnetic resonance imaging (MRI), and therefore, it is unclear whether morphological asymmetries of the POP exist, and whether these asymmetries differ in right- and left-handers. The purpose of this study was to determine if measurable asymmetries of the POP exist on MRI, and whether the direction of the asymmetries differ in right- and left-handers. The PTR and POP were measured on volumetric MRI scans of 16 right-handers and 16 left-handers matched for age and gender. There was a significant leftward asymmetry of the PTR in right- and left-handers, although the asymmetry was reduced in the left-handers. In contrast, there was a leftward asymmetry of the POP in right-handers, and a rightward asymmetry in the left-handers. Handedness, derived from a handedness inventory, was positively correlated with POP asymmetry.
Young and old adults underwent positron emission tomography during the performance of a working memory task for faces (delayed match-to-sample), in which the delay between the sample and choice faces was varied from 1 to 21 s. Reaction time was slower and accuracy lower in the old group, but not markedly so. Values of regional cerebral blood flow (rCBF) were analyzed for sustained activity across delay conditions, as well as for changes as delay increased. Many brain regions showed similar activity during these tasks in both young and old adults, including left anterior prefrontal cortex, which had increased rCBF with delay, and ventral extrastriate cortex, which showed decreased rCBF with delay. However, old adults had less activation overall and less modulation of rCBF across delay in right ventrolateral prefrontal cortex than did the young adults. Old adults also showed greater rCBF activation in left dorsolateral prefrontal cortex across all WM delays and increased rCBF at short delays in left occipitoparietal cortex compared to young adults. Activity in many of these regions was differentially related to performance in that it was associated with decreasing response times in the young group and increasing response times in the older individuals. Thus despite the finding that performance on these memory tasks and associated activity in a number of brain areas are relatively preserved in old adults, differences elsewhere in the brain suggest that different strategies or cognitive processes are used by the elderly to maintain memory representations over short periods of time.
As previous functional neuroimaging studies could not settle the controversy regarding the contribution of dominant and subdominant hemisphere to recovery from poststroke aphasia, language performance was related to H2(15)O-positron emission tomographic activation patterns in 23 right-handed aphasic patients 2 and 8 weeks after stroke. In patients classified according to the site of lesion (frontal, n = 7; subcortical, n = 9; temporal, n = 7) and in 11 control subjects, flow changes caused by a word repetition task were calculated in 14 regions representing eloquent and contralateral homotopic areas. These areas were defined on coregistered magnetic resonance imaging scans and tested for significance (Bonferroni corrected t test, alpha = 0.0036). At baseline, differences in test performance were only found between the subcortical and temporal group. The extent of recovery, however, differed and was reflected in the activation. The subcortical and frontal groups improved substantially; they activated the right inferior frontal gyrus and the right superior temporal gyrus (STG) at baseline and regained left STG activation at follow-up. The temporal group improved only in word comprehension; it activated the left Broca area and supplementary motor areas at baseline and the precentral gyrus bilaterally as well as the right STG at follow-up, but could not reactivate the left STG. These differential activation patterns suggest a hierarchy within the language-related network regarding effectiveness for improvement of aphasia; ie, right hemispheric areas contribute, if left hemispheric regions are destroyed. Efficient restoration of language is usually only achieved if left temporal areas are preserved and can be reintegrated into the functional network.
The use of functional neuroimaging to test hypotheses regarding age-related changes in the neural substrates of cognitive processes relies on assumptions regarding the coupling of neural activity to neuroimaging signal. Differences in neuroimaging signal response between young and elderly subjects can be mapped directly to differences in neural response only if such coupling does not change with age. Here we examined spatial and temporal characteristics of the BOLD fMRI hemodynamic response in primary sensorimotor cortex in young and elderly subjects during the performance of a simple reaction time task. We found that 75% of elderly subjects (n = 20) exhibited a detectable voxel-wise relationship with the behavioral paradigm in this region as compared to 100% young subjects (n = 32). The median number of suprathreshold voxels in the young subjects was greater than four times that of the elderly subjects. Young subjects had a slightly greater signal:noise per voxel than the elderly subjects that was attributed to a greater level of noise per voxel in the elderly subjects. The evidence did not support the idea that the greater head motion observed in the elderly was the cause of this greater voxel-wise noise. There were no significant differences between groups in either the shape of the hemodynamic response or in its the within-group variability, although the former evidenced a near significant trend. The overall finding that some aspects of the hemodynamic coupling between neural activity and BOLD fMRI signal change with age cautions against simple interpretations of the results of imaging studies that compare young and elderly subjects.
Prevalent theories hold that semantic memory is organized by sensorimotor modality (e.g., visual knowledge, motor knowledge). While some neuroimaging studies support this idea, it cannot account for the category specific (e.g., living things) knowledge impairments seen in some brain damaged patients that cut across modalities. In this article we test an alternative model of how damage to interactive, modality-specific neural regions might give rise to these categorical impairments. Functional MRI was used to examine a cortical area with a known modality-specific function during the retrieval of visual and non-visual knowledge about living and non-living things. The specific predictions of our model regarding the signal observed in this area were confirmed, supporting the notion that semantic memory is functionally segregated into anatomically discrete, but highly interactive, modality-specific regions.
Two mechanisms for recovery from aphasia, repair of damaged language networks and activation of compensatory areas, have been proposed. In this study, we investigated whether both mechanisms or one instead of the other take place in the brain of recovered aphasic patients.
Using blood oxygenation level-dependent functional MRI (fMRI), we studied cortical language networks during lexical-semantic processing tasks in 7 right-handed aphasic patients at least 5 months after the onset of left-hemisphere stroke and had regained substantial language functions since then.
We found that in the recovered aphasic patient group, functional language activity significantly increased in the right hemisphere and nonsignificantly decreased in the left hemisphere compared with that in the normal group. Bilateral language networks resulted from partial restitution of damaged functions in the left hemisphere and activation of compensated (or recruited) areas in the right hemisphere. Failure to restore any language function in the left hemisphere led to predominantly right hemispheric networks in some individuals. However, better language recovery, at least for lexical-semantic processing, was observed in individuals who had bilateral rather than right hemisphere-predominant networks.
The results indicate that the restoration of left-hemisphere language networks is associated with better recovery and inversely related to activity in the compensated or recruited areas of the right hemisphere.
Event-related functional MRI and a version of the Stroop color naming task were used to test two conflicting theories of anterior cingulate cortex (ACC) function during executive processes of cognition. A response-related increase in ACC activity was present when strategic processes were less engaged, and conflict high, but not when strategic processes were engaged and conflict reduced. This is inconsistent with the widely held view that the ACC implements strategic processes to reduce cognitive conflicts, such as response competition. Instead, it suggests that the ACC serves an evaluative function, detecting cognitive states such as response competition, which may lead to poor performance, and representing the knowledge that strategic processes need to be engaged.
Working memory (WM), the process by which information is coded into memory, actively maintained and subsequently retrieved, declines with age. To test the hypothesis that age-related changes in prefrontal cortex (PFC) may mediate this WM decline, we used functional MRI to investigate age differences in PFC activity during separate WM task components (encoding, maintenance, retrieval). We found greater PFC activity in younger than older adults only in dorsolateral PFC during memory retrieval. Fast younger subjects showed less dorsolateral PFC activation during retrieval than slow younger subjects, whereas older adults showed the opposite pattern. Thus age-related changes in dorsolateral PFC and not ventrolateral PFC account for WM decline with normal aging.
Studies of a range of higher cognitive functions consistently activate a region of anterior cingulate cortex (ACC), typically posterior to the genu and superior to the corpus collosum. In particular, this ACC region appears to be active in task situations where there is a need to override a prepotent response tendency, when responding is underdetermined, and when errors are made. We have hypothesized that the function of this ACC region is to monitor for the presence of "crosstalk" or competition between incompatible responses. In prior work, we provided initial support for this hypothesis, demonstrating ACC activity in the same region both during error trials and during correct trials in task conditions designed to elicit greater response competition. In the present study, we extend our testing of this hypothesis to task situations involving underdetermined responding. Specifically, 14 healthy control subjects performed a verb-generation task during event-related functional magnetic resonance imaging (fMRI), with the on-line acquisition of overt verbal responses. The results demonstrated that the ACC, and only the ACC, was more active in a series of task conditions that elicited competition among alternative responses. These conditions included a greater ACC response to: (1) Nouns categorized as low vs. high constraint (i.e., during a norming study, multiple verbs were produced with equal frequency vs. a single verb that produced much more frequently than any other); (2) the production of verbs that were weak associates, rather than, strong associates of particular nouns; and (3) the production of verbs that were weak associates for nouns categorized as high constraint. We discuss the implication of these results for understanding the role that the ACC plays in human cognition.
There are a number of age-related structural and physiological changes in the brain that could have implications for cognitive function in the elderly. The impact of these age-related changes in the brain on cognition has been studied using neuroimaging to examine brain activity during tasks of memory, perception and attention, and determine how this activity differs between young and older individuals. It has often been found that older individuals utilize different areas of the brain than do young subjects when carrying out the same cognitive task. This has led some researchers to suggest that older persons utilize different functional brain networks, perhaps to compensate for reductions of efficiency in task-related brain areas. However, data collected to date on this issue are still limited, so although the evidence is intriguing, the definitive interpretation of these findings must await further experiments.
Prefrontal cortex plays a central role in mnemonic control, with left inferior prefrontal cortex (LIPC) mediating control of semantic knowledge. One prominent theory posits that LIPC does not mediate semantic retrieval per se, but rather subserves the selection of task-relevant knowledge from amidst competing knowledge. The present event-related fMRI study provides evidence for an alternative hypothesis: LIPC guides controlled semantic retrieval irrespective of whether retrieval requires selection against competing representations. With selection demands held constant, LIPC activation increased with semantic retrieval demands and with the level of control required during retrieval. LIPC mediates a top-down bias signal that is recruited to the extent that the recovery of meaning demands controlled retrieval. Selection may reflect a specific instantiation of this mechanism.
Brain imaging based on functional MRI (fMRI) provides a powerful tool for characterizing age-related changes in functional anatomy. However, between-population comparisons confront potential differences in measurement properties. The present experiment explores the feasibility of conducting fMRI studies in nondemented and demented older adults by measuring hemodynamic response properties in an event-related design. A paradigm involving repeated presentation of sensory-motor response trials was administered to 41 participants (14 young adults, 14 nondemented older adults, and 13 demented older adults). For half of the trials a single sensory-motor event was presented in isolation and in the other half in pairs. Hemodynamic response characteristics to the isolated events allowed basic response properties (e.g., amplitude and variance) between subject groups to be contrasted. The paired events further allowed the summation properties of the hemodynamic response to be characterized. Robust and qualitatively similar activation maps were produced for all subject groups. Quantitative results showed that for certain regions, such as in the visual cortex, there were marked reductions in the amplitude of the hemodynamic response in older adults. In other regions, such as in the motor cortex, relatively intact response characteristics were observed. These results suggest caution should be exhibited in interpreting simple main effects in response amplitude between subject groups. However, across all regions examined, the summation of the hemodynamic response over trials was highly similar between groups. This latter finding suggests that, even if absolute measurement differences do exist between subject groups, relative activation change should be preserved. Designs that rely on group interactions between task conditions, parametric manipulations, or group interactions between regions should provide valuable data for making inferences about functional-anatomic changes between different populations.
The present study investigated the sensitivity and specificity of the Hopkins Verbal Learning Test (HVLT) for demented patients (n = 82, using NINCDS criteria) and 114 healthy controls--equivalent in age, years of education and gender-ratio--from the Oxford Project to Investigate Memory and Ageing. The HVLT 'Total Recall' score had 87% sensitivity and 98% specificity for dementia using a cut-off score of 14.5. Using a 'Memory' score (the sum of the 'Total Recall' and the 'Discrimination Index') with a cut-off score of 24.5 gave a 91% sensitivity and 98% specificity for Alzheimer's disease cases when compared to controls. Unlike the MMSE, the HVLT has no ceiling effects and does not have to be adjusted for education. We conclude that the HVLT is an easy to administer, quick and well tolerated tool for the screening of dementia.