No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Event-Related Dynamics of Brain Oscillations
Abstract
Language comprehension involves two basic operations: the retrieval of lexical information (such as phonologic, syntactic, and semantic information) from long-term memory, and the unification of this information into a coherent representation of the overall utterance. Neuroimaging studies using hemodynamic measures such as PET and fMRI have provided detailed information on which areas of the brain are involved in these language-related memory and unification operations. However, much less is known about the dynamics of the brain's language network. This chapter presents a literature review of the oscillatory neuronal dynamics of EEG and MEG data that can be observed during language comprehension tasks. From a detailed review of this (rapidly growing) literature the following picture emerges: memory retrieval operations are mostly accompanied by increased neuronal synchronization in the theta frequency range (4–7 Hz). Unification operations, in contrast, induce high-frequency neuronal synchronization in the beta (12–30 Hz) and gamma (above 30 Hz) frequency bands. A desynchronization in the (upper) alpha frequency band is found for those studies that use secondary tasks, and seems to correspond with attentional processes, and with the behavioral consequences of the language comprehension process. We conclude that it is possible to capture the dynamics of the brain's language network by a careful analysis of the event-related changes in power and coherence of EEG and MEG data in a wide range of frequencies, in combination with subtle experimental manipulations in a range of language comprehension tasks. It appears then that neuronal synchrony is a mechanism by which the brain integrates the different types of information about language (such as phonological, orthographic, semantic, and syntactic information) represented in different brain areas.
... Thus, our data provide further support for a close association between theta activity and the retrieval of semantic information from long-term memory, which has been proposed for both, language processing (Bastiaansen and Hagoort, 2006) and mathematical cognition (De Smedt et al., 2009; Grabner and De Smedt, 2011). Theta activity is assumed to be involved in functionally linking the cortex with the medial temporal lobe (in particular the hippocampus; Bastiaansen and Hagoort, 2003; Klimesch et al., 2005), which is known to play an important role in memory encoding (Gabrieli, 1998) and in retrieval of facts from memory (e.g., Squire et al., 2004) This assumption fits nicely with findings from several recent fMRI studies, showing that parietal cortical areas as well as the medial temporal lobe are involved in mental arithmetic. ...
... Studies applying the ERS/ERD methodology have accumulated much evidence suggesting differential functional significance of various frequency bands. Bandpower increases (ERS) in theta activity (about 3–6 Hz) have been associated with memory encoding and retrieval, in general (Klimesch et al., 1997; Burgess and Gruzelier, 2000; Jensen and Tesche, 2002), and with retrieval of lexical-semantic information from long-term memory, in particular (Bastiaansen et al., 2005; Bastiaansen and Hagoort 2006; Grabner et al., 2007b). Bandpower decreases (ERD) in alpha activity (about 8–13 Hz) have been observed to vary with task difficulty in various cognitive demands (Neubauer et al., 2006; Ku et al., 2010) and thus have been interpreted as general index of invested cognitive resources (Pfurtscheller and Lopes Da Silva, 1999b). ...
... In addition to analyses of the functional topography using fMRI and the time-course of brain activity based on ERPs, there is growing interest into oscillatory EEG activity during problem solving, specifically into strategy-related changes in brain oscillations (i.e., induced EEG activity). These changes are related to the coupling and uncoupling of functional networks in the brain and, thus, provide incremental insights into how task-related neuronal networks are formed and interact with each other (Neuper and Pfurtscheller, 2001; Klimesch et al., 2005; Bastiaansen and Hagoort, 2006). Moreover, in contrast to ERPs whose analysis requires averaging over 50–100 trials, reliable measures of induced EEG activity can be obtained based on only a few trials, which makes it a promising candidate for the development of electrophysiological markers of strategy use (De Smedt et al., 2009; Grabner and De Smedt, 2011). ...
There has been a long tradition of research on mathematics education showing that children and adults use different strategies to solve arithmetic problems. Neurophysiological studies have recently begun to investigate the brain correlates of these strategies. The existing body of data, however, reflect static end points of the learning process and do not provide information on how brain activity changes in response to training or intervention. In this study, we explicitly address this issue by training participants in using fact retrieval strategies. We also investigate whether brain activity related to arithmetic fact learning is domain-specific or whether this generalizes to other learning materials, such as the solution of figural-spatial problems. Twenty adult students were trained on sets of two-digit multiplication problems and figural-spatial problems. After the training, they were presented with the trained and untrained problems while their brain activity was recorded by means of electroencephalography (EEG). In both problem types, the training resulted in accuracies over 90% and significant decreases in solution times. Analyses of the oscillatory EEG data also revealed training effects across both problem types. Specifically, we observed training-related activity increases in the theta band (3–6 Hz) and decreases in the lower alpha band (8–10 Hz), especially over parietooccipital and parietal brain regions. These results provide the first evidence that a short-term fact retrieval training results in significant changes in oscillatory EEG activity. These findings further corroborate the role of the theta band in the retrieval of semantic information from memory and suggest that theta activity is sensitive to fact retrieval not only in mental arithmetic but also in other domains.
... Examination of language at the neuronal level has already started gaining popularity both in studies of the healthy brain (e.g., [47]) and in studies of treatment-based changes in language performance during aphasia recovery (e.g., [81]). The premise of these studies is that abstract language models are inherently unable to detail neuronal circuitry and therefore have little utility for neurobiological studies of language (e.g., [81]). ...
... In contrast, Hagoort [43] has argued for a model that implies the operation of distributed neural networks, in which language processing (comprehension and production) in Broca's area, the left inferior frontal gyrus (LIFG), involves parallel processing of semantic, syntactic, and phonological information, accomplished via three functional components: memory, unification, and control, memory, to retrieve language information stored in long-term memory, unification, to integrate the retrieved information into larger (multiword) units, and control, to select what he terms a language “action.” Using evidence from EEG and MEG studies, he has been able to identify the specific temporal features of unification and memory retrieval, arguing for neuronal synchronization that supports functional interrelatedness rather than strict domain specificity [47]. ...
THIS REVIEW PAPER PRESENTS CONVERGING EVIDENCE FROM STUDIES OF BRAIN DAMAGE AND LONGITUDINAL STUDIES OF LANGUAGE IN AGING WHICH SUPPORTS THE FOLLOWING THESIS: the neural basis of language can best be understood by the concept of neural multifunctionality. In this paper the term "neural multifunctionality" refers to incorporation of nonlinguistic functions into language models of the intact brain, reflecting a multifunctional perspective whereby a constant and dynamic interaction exists among neural networks subserving cognitive, affective, and praxic functions with neural networks specialized for lexical retrieval, sentence comprehension, and discourse processing, giving rise to language as we know it. By way of example, we consider effects of executive system functions on aspects of semantic processing among persons with and without aphasia, as well as the interaction of executive and language functions among older adults. We conclude by indicating how this multifunctional view of brain-language relations extends to the realm of language recovery from aphasia, where evidence of the influence of nonlinguistic factors on the reshaping of neural circuitry for aphasia rehabilitation is clearly emerging.
... Applying such techniques to EEG recorded during language comprehension has shown that different aspects of language comprehension systematically affect power and coherence estimates in different frequency ranges (see Bastiaansen and Hagoort, 2006 for a review). For example, retrieval of word-level information is mostly accompanied by increased neuronal synchronization in the theta frequency range (4–7 Hz; Bastiaansen et al., 2005, 2008). ...
... What all these findings have in common, is an increase in gamma (∼40 Hz) power or coherence when semantic unification can be routinely performed, and a disruption of this gamma increase when semantic anomalies are encountered. Based on these findings, we have proposed (Varela et al., 2001; Bastiaansen and Hagoort, 2006) that gamma-band neuronal synchronization is related to normal, ongoing semantic unification operations. Two recent studies, in which gamma power time courses were computed across entire sentences, further support this proposition. ...
Gamma-band neuronal synchronization during sentence-level language comprehension has previously been linked with semantic unification. Here, we attempt to further narrow down the functional significance of gamma during language comprehension, by distinguishing between two aspects of semantic unification: successful integration of word meaning into the sentence context, and prediction of upcoming words. We computed event-related potentials (ERPs) and frequency band-specific electroencephalographic (EEG) power changes while participants read sentences that contained a critical word (CW) that was (1) both semantically congruent and predictable (high cloze, HC), (2) semantically congruent but unpredictable (low cloze, LC), or (3) semantically incongruent (and therefore also unpredictable; semantic violation, SV). The ERP analysis showed the expected parametric N400 modulation (HC < LC < SV). The time-frequency analysis showed qualitatively different results. In the gamma-frequency range, we observed a power increase in response to the CW in the HC condition, but not in the LC and the SV conditions. Additionally, in the theta frequency range we observed a power increase in the SV condition only. Our data provide evidence that gamma power increases are related to the predictability of an upcoming word based on the preceding sentence context, rather than to the integration of the incoming word’s semantics into the preceding context. Further, our theta band data are compatible with the notion that theta band synchronization in sentence comprehension might be related to the detection of an error in the language input.
... The users are supposed to perform such imagery tasks without actually performing the related movement and by doing so produce activity patterns in corresponding cortical areas. These patterns are called event- related desynchronization (ERD) and event-related synchronization (ERS) [6] ...
Brain-computer interfaces (BCIs) are able to measure the activity of the human brain and detect and discriminate specific brain patterns. The main application of BCIs has been and is to control assistive devices and provide communication for people who have lost voluntary control of their muscle activity. Recent progress in BCI research, however, has broadened the field of possible applications. Intelligent devices that can compensate for the unreliability of and lack of information content in the BCI signal may become useful for less disabled people as well. Also, neurological rehabilitation and neurofeedback therapies are new emerging BCI applications, where the focus is not on communica-tion and control, but primarily on facilitating effective physiologi-cal regulation and cortical reorganization of brain structures. Regardless of the application, learning to voluntarily modulate brain patterns is an integral part of endogenous BCIs. Present-day BCIs seldom provide accurate feedback within an interesting and graphically appealing training environment. Specially designed computer games that provide both a motivational environment and appropriate feedback which facilitates effective learning may be necessary to motivate the users for the long training periods necessary in BCI rehabilitation and neurofeedback therapy applications.
... Previous studies of the processing of visually presented word and word-like stimuli using positron emission tomography (PET) (Petersen et al., 1988, 1990; Petersen and Fiez, 1993; Liotti et al., 1994; Price et al., 1996) and functional magnetic resonance imaging (fMRI) (Puce et al., 1996; Indefrey et al., 1997; Cohen et al., 2000, 2002; Tagamets et al., 2000; Baker et al., 2007), have emphasized the left-lateralized nature of word-form processing in occipital cortex (reviewed in Bastiaansen and Hagoort, 2006; Dien, 2009b). In general, these studies have found that visually presented real words and pseudowords (pronounceable non-words), relative to non-word control stimuli (e.g., consonant strings and digits), selectively elicit enhanced activity in portions of the left medial occipital cortex. ...
The decoding of visually presented line segments into letters, and letters into words, is critical to fluent reading abilities. Here we investigate the temporal dynamics of visual orthographic processes, focusing specifically on right hemisphere contributions and interactions between the hemispheres involved in the implicit processing of visually presented words, consonants, false fonts, and symbolic strings. High-density EEG was recorded while participants detected infrequent, simple, perceptual targets (dot strings) embedded amongst a of character strings. Beginning at 130 ms, orthographic and non-orthographic stimuli were distinguished by a sequence of ERP effects over occipital recording sites. These early latency occipital effects were dominated by enhanced right-sided negative-polarity activation for non-orthographic stimuli that peaked at around 180 ms. This right-sided effect was followed by bilateral positive occipital activity for false-fonts, but not symbol strings. Moreover the size of components of this later positive occipital wave was inversely correlated with the right-sided ROcc180 wave, suggesting that subjects who had larger early right-sided activation for non-orthographic stimuli had less need for more extended bilateral (e.g., interhemispheric) processing of those stimuli shortly later. Additional early (130–150 ms) negative-polarity activity over left occipital cortex and longer-latency centrally distributed responses (>300 ms) were present, likely reflecting implicit activation of the previously reported ‘visual-word-form’ area and N400-related responses, respectively. Collectively, these results provide a close look at some relatively unexplored portions of the temporal flow of information processing in the brain related to the implicit processing of potentially linguistic information and provide valuable information about the interactions between hemispheres supporting visual orthographic processing.
... In this context, at least two types of EEG parameters with diVerential functional signiWcance have to be distinguished: (a) analyses of (taskrelated changes in) the amplitude of EEG background activity in diVerent frequency bands [17] [28] and (b) analyses of functional couplings (in amplitude and/or phase) between diVerent electrode sites [12] [13]. In studies from our research group, we primarily focused on task-related EEG power changes in the alpha frequency band as this measure has proved to be a useful and appropriate technique to measure the level and also the topographical distribution of cortical activity during cognitive task performance [29]. ...
The psychometric assessment of different facets of creative abilities as well as the availability of experimental tasks for the neuroscientific study of creative thinking has replaced the view of creativity as an unsearchable trait. In this article we provide a brief overview of contemporary methodologies used for the operationalization of creative thinking in a neuroscientific context. Empirical studies are reported which measured brain activity (by means of EEG, fMRI, NIRS or PET) during the performance of different experimental tasks. These tasks, along with creative idea generation tasks used in our laboratory, constitute useful tools in uncovering possible brain correlates of creative thinking. Nevertheless, much more work is needed in order to establish reliable and valid measures of creative thinking, in particular measures of novelty or originality of creative insights.
El objetivo general de este trabajo es el desarrollo de técnicas de análisis de polisomnogramas (PSG) con el objetivo de extraer automáticamente hipnogramas en Matlab. Los registros PSG incluyen principalmente señales electroencefalográficas (EEG), electromiográficas (EMG), electrooculográficas (EOG). Estas medidas se han usado para dividir el sueño (estado biológico no-uniforme) en diferentes estados o etapas. La diagnosis y el tratamiento de pacientes con desordenes del sueño requiere de la clasificación de los PSGs en los diferentes estados del sueño. Normalmente, el sueño sano está organizado en secuencias de etapas en ciclos de 60-90 minutos. Dependiendo de los estándares adoptados, las diferentes etapas se derivan de cuatro estados básicos del sueño biológico: Despierto, Sueño Ligero, Sueño Profundo, y Sueño de Movimiento Rápido de Ojos (REM, del inglés Rapid Eye Movement). El hipnograma es un diagrama con la descripción evolutiva en el tiempo de las etapas de sueño. Este diagrama es usado por los médicos para diagnosis de desordenes del sueño tales como insomnio, apnea, y narcolepsia.
Neuroscientific studies revealed first insights into neural mechanisms underlying creativity, but existing findings are highly variegated and often inconsistent. Despite the disappointing picture on the neuroscience of creativity drawn in recent reviews, there appears to be robust evidence that EEG alpha power is particularly sensitive to various creativity-related demands involved in creative ideation. Alpha power varies as a function of creativity-related task demands and the originality of ideas, is positively related to an individuals' creativity level, and has been observed to increase as a result of creativity interventions. Alpha increases during creative ideation could reflect more internally oriented attention that is characterized by the absence of external bottom-up stimulation and, thus, a form of top-down activity. Moreover, they could indicate the involvement of specific memory processes such as the efficient (re-)combination of unrelated semantic information. We conclude that increased alpha power during creative ideation is among the most consistent findings in neuroscientific research on creativity and discuss possible future directions to better understand the manifold brain mechanisms involved in creativity.
The relationship between the evoked responses (ERPs/ERFs) and the event-related changes in EEG/MEG power that can be observed during sentence-level language comprehension is as yet unclear. This study addresses a possible relationship between MEG power changes and the N400m component of the event-related field. Whole-head MEG was recorded while subjects listened to spoken sentences with incongruent (IC) or congruent (C) sentence endings. A clear N400m was observed over the left hemisphere, and was larger for the IC sentences than for the C sentences. A time-frequency analysis of power revealed a decrease in alpha and beta power over the left hemisphere in roughly the same time range as the N400m for the IC relative to the C condition. A linear regression analysis revealed a positive linear relationship between N400m and beta power for the IC condition, not for the C condition. No such linear relation was found between N400m and alpha power for either condition. The sources of the beta decrease were estimated in the LIFG, a region known to be involved in semantic unification operations. One source of the N400m was estimated in the left superior temporal region, which has been related to lexical retrieval. We interpret our data within a framework in which beta oscillations are inversely related to the engagement of task-relevant brain networks. The source reconstructions of the beta power suppression and the N400m effect support the notion of a dynamic communication between the LIFG and the left superior temporal region during language comprehension. Hum Brain Mapp, 2012. © 2012 Wiley Periodicals, Inc.
Behavioral research has shown that arithmetic problems (e.g., 6+2=) are solved with various strategies, which can be inferred from the size of the presented problems or from trial-by-trial verbal strategy reports. The validity of these verbal strategy reports, however, has been repeatedly questioned. In the present electroencephalography study, we compared the association of both approaches with the oscillatory brain responses during arithmetic problem solving. Nineteen adults solved small and large addition and subtraction problems and indicated the applied strategy (fact retrieval vs. procedure use) on a trial-by-trial basis by means of verbal strategy reports. Analysis of event-related (de-)synchronization (ERS/ERD) in theta and alpha frequencies revealed a general convergence of verbal strategy reports and the problem size approach, with fact retrieval being accompanied by higher left-hemispheric theta ERS, and procedural strategies being reflected in higher widespread ERD in the lower alpha band and bilateral parietooccipital ERD in the upper alpha band. A direct comparison of the neurophysiological data from both approaches suggests a higher sensitivity of verbal strategy reports to problem solving strategies applied in mental arithmetic, particularly for large problems. Taken together, the current data provide the first neurophysiological evidence for the validity of verbal strategy reports.
To analyze the event-related desynchronization/synchronization (ERD/ERS) attended with the mental load arising while solving two cognitive tasks. The features of the presented visual stimulus determined the type of cognitive task that should be solved.
For each experimental task and everybody's subject FFT Analysis module calculated the total power histograms from a fixed frequency band (3-20 Hz or 8-13 Hz) for each 3-second EEG sample with 50 % overlay and all electrodes. From the histograms the software derived two FFT single values--the average Total Power (TP) and Frequency at Maximum Power (FMP).
It has been shown that during the solution of cognitive tasks the marked changes of ongoing EEG activity appeared. The short lasting and localized amplitude decrease in rhythmic activity (ERD) and the change of EEG frequency were among the most frequent. The ERD extent was determined by an informational content of processed visual stimuli and by the site of scalp-recording electrode. A higher mental load related to the solution of cognitive tasks shifted the average FM to lower frequencies.
The suitability of an analysis of ongoing EEG activity to uncover differences in people's brain activation patterns when engaged in performing cognitively demanding tasks was proved.
In the present study, we contrast oscillatory brain activity during the production of subjectively more versus less original ideas. A sample of 26 participants worked on two verbal creativity problems and subsequently rated the produced ideas with respect to their originality. On the basis of these self-ratings, ideas were divided into a more and a less original list within each participant. Cortical activity was assessed by means of event-related changes in EEG power (synchronization and desynchronization) and phase locking in two alpha bands. Analyses revealed that more, as compared with less, original ideas elicited a stronger event-related synchronization of alpha activity (power increases from the pre-stimulus reference to the activation interval) and higher phase coupling in the right hemisphere. These findings corroborate the importance of right-hemispheric cortical networks in creative idea generation.
Synchronized low-frequency spontaneous fluctuations of the functional MRI (fMRI) signal have recently been applied to investigate large-scale neuronal networks of the brain in the absence of specific task instructions. However, the underlying neural mechanisms of these fluctuations remain largely unknown. To this end, electrophysiological recordings and resting-state fMRI measurements were conducted in α-chloralose-anesthetized rats. Using a seed-voxel analysis strategy, region-specific, anesthetic dose-dependent fMRI resting-state functional connectivity was detected in bilateral primary somatosensory cortex (S1FL) of the resting brain. Cortical electroencephalographic signals were also recorded from bilateral S1FL; a visual cortex locus served as a control site. Results demonstrate that, unlike the evoked fMRI response that correlates with power changes in the γ bands, the resting-state fMRI signal correlates with the power coherence in low-frequency bands, particularly the δ band. These data indicate that hemodynamic fMRI signal differentially registers specific electrical oscillatory frequency band activity, suggesting that fMRI may be able to distinguish the ongoing from the evoked activity of the brain.
• electroencephalogram
• spontaneous fluctuations
• functional connectivity
Cortical activity in the EEG alpha band has proven to be particularly sensitive to creativity-related demands, but its functional meaning in the context of creative cognition has not been clarified yet. Specifically, increases in alpha activity (i.e., alpha synchronisation) in response to creative thinking can be interpreted in different ways: As a functional correlate of cortical idling, as a sign of internal top-down activity or, more specifically, as selective inhibition of brain regions. We measured brain activity during creative thinking in two studies employing different neurophysiological measurement methods (EEG and fMRI). In both studies, participants worked on four verbal tasks differentially drawing on creative idea generation. The EEG study revealed that the generation of original ideas was associated with alpha synchronisation in frontal brain regions and with a diffuse and widespread pattern of alpha synchronisation over parietal cortical regions. The fMRI study revealed that task performance was associated with strong activation in frontal regions of the left hemisphere. In addition, we found task-specific effects in parietotemporal brain areas. The findings suggest that EEG alpha band synchronisation during creative thinking can be interpreted as a sign of active cognitive processes rather than cortical idling.
ResearchGate has not been able to resolve any references for this publication.