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Seeing and hearing speech excites the motor system involved in speech production
Abstract
The perception of action is associated with increased activity in motor regions, implicating such regions in the recognition, understanding and imitation of actions. We examined the possibility that perception of speech, both auditory and visual, would also result in changes in the excitability of the motor system underlying speech production. Transcranial magnetic stimulation was applied to the face area of primary motor cortex to elicit motor-evoked potentials in the lip muscles. The size of the motor-evoked potentials was compared under the following conditions: listening to speech, listening to non-verbal sounds, viewing speech-related lip movements, and viewing eye and brow movements. Compared to control conditions, listening to and viewing speech enhanced the size of the motor-evoked potential. This effect was only seen in response to stimulation of the left hemisphere; stimulation of the right hemisphere produced no changes in motor-evoked potentials in any of the conditions. In a control experiment, the size of the motor-evoked potentials elicited in the muscles of the right hand did not differ among conditions, suggesting that speech-related changes in excitability are specific to the lip muscles. These results provide evidence that both auditory and visual speech perception facilitate the excitability of the motor system involved in speech production.
... Furthermore, participation of the prefrontal speech motor areas in the middle frontal gyrus (MFG), inferior frontal gyrus (IFG), supramarginal gyrus (SMG), and premotor cortex has been found when viewing orofacial movements (Nishitani & Hari, 2002), indicating the involvement of a mirror neuron-like system. The speech motor system was activated when participants attempted to lipread vowels (Callan et al., 2014), syllables (Skipper et al., 2007), words (Paulesu et al., 2003;Watkins et al., 2003), and short stories (Skipper et al., 2005). More recently, it has been suggested that a specific temporal visual speech area (TVSA), in the posterior temporal cortex, ventral and posterior to the multisensory posterior superior temporal sulcus (pSTS), supports sensory-motor integration (Bernstein & Liebenthal, 2014;Bernstein et al., 2011), because its strength of activation has been found to be related to the number of correctly recognized nonsense syllables (n = 10). ...
... We also found lipreading-related activation in the primary motor cortex in the left hemisphere similarly to listening (Figure 3a), but not reading ( Figure 3b). In line with previous studies with isolated, simple linguistic stimuli, brain areas related to speech production were activated during lipreading (Callan et al., 2014;Skipper et al., 2005Skipper et al., , 2007Watkins et al., 2003). Apparently, motor knowledge of articulatory gestures modulates auditory-cortical processing through reciprocal sensory-motor connections (Chu et al., 2013;Kauramäki et al., 2010;Skipper et al., 2005Skipper et al., , 2007. ...
... Apparently, motor knowledge of articulatory gestures modulates auditory-cortical processing through reciprocal sensory-motor connections (Chu et al., 2013;Kauramäki et al., 2010;Skipper et al., 2005Skipper et al., , 2007. Furthermore, motor knowledge of our own speech production is used in lipreading others (Calvert & Campbell, 2003;Nishitani & Hari, 2002;Paulesu et al., 2003;Watkins et al., 2003). ...
Introduction
Few of us are skilled lipreaders while most struggle with the task. Neural substrates that enable comprehension of connected natural speech via lipreading are not yet well understood.
Methods
We used a data‐driven approach to identify brain areas underlying the lipreading of an 8‐min narrative with participants whose lipreading skills varied extensively (range 6–100%, mean = 50.7%). The participants also listened to and read the same narrative. The similarity between individual participants’ brain activity during the whole narrative, within and between conditions, was estimated by a voxel‐wise comparison of the Blood Oxygenation Level Dependent (BOLD) signal time courses.
Results
Inter‐subject correlation (ISC) of the time courses revealed that lipreading, listening to, and reading the narrative were largely supported by the same brain areas in the temporal, parietal and frontal cortices, precuneus, and cerebellum. Additionally, listening to and reading connected naturalistic speech particularly activated higher‐level linguistic processing in the parietal and frontal cortices more consistently than lipreading, probably paralleling the limited understanding obtained via lip‐reading. Importantly, higher lipreading test score and subjective estimate of comprehension of the lipread narrative was associated with activity in the superior and middle temporal cortex.
Conclusions
Our new data illustrates that findings from prior studies using well‐controlled repetitive speech stimuli and stimulus‐driven data analyses are also valid for naturalistic connected speech. Our results might suggest an efficient use of brain areas dealing with phonological processing in skilled lipreaders.
... Counter evidence to the motor theory comes from findings that speech perception can be achieved without speech motor ability in infants [34], non-human animals [35], and people suffering from aphasia [36][37][38]. However, there is also increasing evidence that perceiving speech involves neural activity of the motor system [39,40], and the motor regions are recruited during listening [41][42][43][44]. A range of brain studies using methods like TMS also showed evidence for the motor theory [45][46][47]. ...
... Here, after being received by the ear, and having gone through the primary auditory analysis, the acoustic signals of speech are first turned into featural patterns that are either auditory (intervals CD) or motor (interval GF). Either way, they are both sub-phonemic and featural, and need to be further processed to identify the categorical phonemes, syllables, words, etc. perceiving speech involves neural activity of the motor system [39,40], and the motor regions are recruited during listening [41][42][43][44]. A range of brain studies using methods like TMS also showed evidence for the motor theory [45][46][47]. ...
It has been widely assumed that in speech perception it is imperative to first detect a set of distinctive properties or features and then use them to recognize phonetic units like consonants, vowels, and tones. Those features can be auditory cues or articulatory gestures, or a combination of both. There have been no clear demonstrations of how exactly such a two-phase process would work in the perception of continuous speech, however. Here we used computational modelling to explore whether it is possible to recognize phonetic categories from syllable-sized continuous acoustic signals of connected speech without intermediate featural representations. We used Support Vector Machine (SVM) and Self-organizing Map (SOM) to simulate tone perception in Mandarin, by either directly processing f0 trajectories, or extracting various tonal features. The results show that direct tone recognition not only yields better performance than any of the feature extraction schemes, but also requires less computational power. These results suggest that prior extraction of features is unlikely the operational mechanism of speech perception.
... Counter evidence to the motor theory comes from findings that speech perception can be achieved without speech motor ability in infants [34], non-human animals [35], and people suffering from aphasia [36][37][38]. However, there is also increasing evidence that perceiving speech involves neural activity of the motor system [39,40], and the motor regions are recruited during listening [41][42][43][44]. A range of brain studies using methods like TMS also showed evidence for the motor theory [45][46][47]. ...
... Here, after being received by the ear, and having gone through the primary auditory analysis, the acoustic signals of speech are first turned into featural patterns that are either auditory (intervals CD) or motor (interval GF). Either way, they are both sub-phonemic and featural, and need to be further processed to identify the categorical phonemes, syllables, words, etc. perceiving speech involves neural activity of the motor system [39,40], and the motor regions are recruited during listening [41][42][43][44]. A range of brain studies using methods like TMS also showed evidence for the motor theory [45][46][47]. ...
Abstract: It has been widely assumed that in speech perception it is imperative to first detect a set of distinctive properties or features and then use them to recognize phonetic units like consonants, vowels, and tones. Those features can be auditory cues or articulatory gestures, or a combination of both. There have been no clear demonstrations of how exactly such a two-phase process would work in the perception of continuous speech, however. Here we used computational modelling to explore whether it is possible to recognize phonetic categories from syllable-sized continuous acoustic signals of connected speech without intermediate featural representations. We used Sup-port Vector Machine (SVM) and Self-organizing Map (SOM) to simulate tone perception in Mandarin, by either directly processing f0 trajectories, or extracting various tonal features. The results show that direct tone recognition not only yields better performance than any of the feature extraction schemes, but also requires less computational power. These results suggest that prior extraction of features is unlikely the operational mechanism of speech perception.
... For language processing, we find significant frontal cortex involvement, including the well-known left hemisphere Broca's area (Flinker et al., 2015), areas throughout the temporal cortex, and the cingulate and precuneus, with the latter being involved in sentence generation and metaphor comprehension (Cavanna and Trimble, 2006). We also note the significant involvement of the premotor cortex, which may underlie speech production (Wildgruber et al., 1996;Watkins et al., 2003) as well as provide further support for the importance of motor skills for language development (Libertus and Violi, 2016). Finally, areas associated with visual reception include, as expected, visual and motor cortices, as well as the supramarginal gyrus, which integrates visual and sensory information, and the insular cortex, which is also involved in somatosensory functioning (Karnath et al., 2005). ...
Three important themes in neuroscience are parcellation, structure-function specificity, and neural plasticity. These themes relate to: 1. The ability to delineate brain regions, for example on the basis of their cellular composition, myeloarchitecture, microstructural architecture, and/or connectivity profiles; 2. Relate parcellations to specific cognitive functions or behaviors; and 3. The ability of the tissue microstructure and architecture to adaptively change in response to environmental influences, with concurrent functional consequences. Neural plasticity suggests that any regional delineation scheme is likely to change with age and functional development, which we can exploit to identify functionally relevant regions and their development with age. From a large longitudinal cohort of neurotypically-developing children, 0 to 13 years of age, we used a data-driven approach to subdivide the cortex based on cortical myelination patterns. Next, we quantified the relationships between rates of myelination across each region and rates of functional development (including motor, language, visuospatial, executive, and academic ability). Linking these evolving processes, we identified unique and overlapping cortical regions that underly diverse skill development, providing new insight into how the cortical myeloarchitecture develops throughout early childhood and its importance to developing cognitive functioning.
... Action observation engages neural mechanisms of action execution (Buccino et al., 2001;Fadiga et al., 1995;Nishitani & Hari, 2002). For vocal actions, the engagement of speech-production mechanisms in speech perception has been demonstrated using functional magnetic resonance imaging (fMRI) (Park, 2020;Pulvermüller et al., 2006;Wilson et al., 2004), transcranial magnetic stimulation (TMS) (Fadiga et al., 2002;Murakami et al., 2011;Watkins et al., 2003), and electroencephalography (EEG) (Michaelis et al., 2021;Oliveira et al., 2021;Pastore et al., 2022). Simulation accounts of speech perception (Pickering & Garrod, 2013;Wilson & Knoblich, 2005) propose that speech actions are automatically and covertly imitated by listeners. ...
Simulation accounts of speech perception posit that speech is covertly imitated to support perception in a top-down manner. Behaviourally, covert imitation is measured through the stimulus-response compatibility (SRC) task. In each trial of a speech SRC task, participants produce a target speech sound whilst perceiving a speech distractor that either matches the target (compatible condition) or does not (incompatible condition). The degree to which the distractor is covertly imitated is captured by the automatic imitation effect, computed as the difference in response times (RTs) between compatible and incompatible trials. Simulation accounts disagree on whether covert imitation is enhanced when speech perception is challenging or instead when the speech signal is most familiar to the speaker. To test these accounts, we conducted three experiments in which participants completed SRC tasks with native and non-native sounds. Experiment 1 uncovered larger automatic imitation effects in an SRC task with non-native sounds than with native sounds. Experiment 2 replicated the finding online, demonstrating its robustness and the applicability of speech SRC tasks online. Experiment 3 intermixed native and non-native sounds within a single SRC task to disentangle effects of perceiving non-native sounds from confounding effects of producing non-native speech actions. This last experiment confirmed that automatic imitation is enhanced for non-native speech distractors, supporting a compensatory function of covert imitation in speech perception. The experiment also uncovered a separate effect of producing non-native speech actions on enhancing automatic imitation effects.
Supplementary Information
The online version contains supplementary material available at 10.3758/s13423-023-02394-z.
... Some research on infants and animals provides counter-evidence to these theories (Eimas et al., 1971). However, the neural activity of the motor system takes place in speech recognition, and motor areas are appointed while listening (Watkins et al., 2003). There is a shred of increasing evidence that motor areas are activated during special auditory situations and may not be involved during normal speech perception (Schmitz et al., 2019). ...
Pahari is an under-resourced, endangered, and undocumented tonal language, spoken in Pakistan Administered State of the Azad Jammu and Kashmir (AJK). Preliminary studies have established the notion, that the Pahari language has three discrete level tones; high, mid, and low. In the current study, tone distribution in monosyllabic words is measured with 45 iterations consisting of 15 high, 15 mid, and 15 low tones, collected from 5 native speakers of Pahari language. An attempt has been made to automatically recognize the phonologically contrastive tones in Pahari language, by using the Random Forest and the Linear Mixed Effect Models with f0 as a preliminary feature along with duration, intensity, F1, F3, and (Cepstral Peak Prominence) CPP. The results showed that the overall accuracy of the Random Forest was higher than the accuracy of the linear mixed effect model. Additionally, the mean f0 played a highly significant role in the prediction of tone while duration, intensity, F1, F3, and CPP played a less significant role.
... Neuroscientific studies first established a potential role for motor activity during low difficulty speech perception. For example, studies employing transcranial magnetic stimulation (TMS) and associated motor evoked potentials (Fadiga et al., 2002;Watkins et al., 2003) and functional magnetic resonance imaging (fMRI; Wilson et al., 2004) showed that neural excitability increases in the articulatory motor cortex during speech perception in quiet. Evidence then emerged to suggest that motor activity is increased during difficult speech perception in younger adults in studies employing TMS (Adank, 2012;D'Ausilio et al., 2012;Nuttall et al., 2016Nuttall et al., , 2017 and fMRI (Du et al., 2014). ...
Speech motor resources may be recruited to assist challenging speech perception in younger normally hearing listeners, but the extent to which this occurs for older adult listeners is unclear. We investigated if speech motor resources are also recruited in older adults during speech perception. Specifically, we investigated if suppression of speech motor resources via sub-vocal rehearsal affects speech perception compared to non-speech motor suppression (jaw movement) and passive listening. Participants identified words in speech-shaped noise at signal-to-noise ratios (SNRs) from -16 to +16 dB in three listening conditions during which participants: (1) opened and closed their jaw (non-speech movement); (2) sub-vocally mimed 'the' (articulatory suppression); (3) produced no concurrent movement (passive listening). Data from 46 younger adults (M age = 20.17 years, SD = 1.61, 36 female) and 41 older adults (M age = 69 years, SD = 5.82, 21 female) were analysed. Linear mixed effects modelling investigated the impact of age, listening condition, and self-reported hearing ability on speech perception (d' prime). Results indicated that speech perception ability was significantly worse in older adults relative to younger adults across all listening conditions. A significant interaction between age group and listening condition indicated that younger adults showed poorer performance during articulatory suppression compared to passive listening, but older adults performed equivalently across conditions. This finding suggests that speech motor resources are less available to support speech perception in older adults, providing important insights for auditory-motor integration for speech understanding and communication in ageing.
... Speech intelligibility is an inherently multi-dimensional process that includes exquisite interactions between sensory-motor systems, language networks, and top-down attentional networks that include cognition and arousal [46][47][48][49][50][51][52][53][54][55][56] . A combination of influences due to diverse factors such as peripheral hearing thresholds, cochlear health, central auditory processing, arousal state, cognitive status, current emotional status, and familiarity with context of the conversation affects multi-talker speech intelligibility 53,[57][58][59][60][61][62][63] . ...
Optimal speech perception in noise requires successful separation of the target speech stream from multiple competing background speech streams. The ability to segregate these competing speech streams depends on the fidelity of bottom-up neural representations of sensory information in the auditory system and top-down influences of effortful listening. Here, we use objective neurophysiological measures of bottom-up temporal processing using envelope-following responses (EFRs) to amplitude modulated tones and investigate their interactions with pupil-indexed listening effort, as it relates to performance on the Quick speech in noise (QuickSIN) test in young adult listeners with clinically normal hearing thresholds. We developed an approach using ear-canal electrodes and adjusting electrode montages for modulation rate ranges, which extended the rage of reliable EFR measurements as high as 1024Hz. Pupillary responses revealed changes in listening effort at the two most difficult signal-to-noise ratios (SNR), but behavioral deficits at the hardest SNR only. Neither pupil-indexed listening effort nor the slope of the EFR decay function independently related to QuickSIN performance. However, a linear model using the combination of EFRs and pupil metrics significantly explained variance in QuickSIN performance. These results suggest a synergistic interaction between bottom-up sensory coding and top-down measures of listening effort as it relates to speech perception in noise. These findings can inform the development of next-generation tests for hearing deficits in listeners with normal-hearing thresholds that incorporates a multi-dimensional approach to understanding speech intelligibility deficits.
... 9 Furthermore, during listening, brain areas associated with speech production are activated and likely improve comprehension. [10][11][12] Indeed, activity in listeners' motor areas is at least partly temporally aligned with activity in the speaker's motor system. [13][14][15] This involvement of the cortical motor system in the alignment between speaker and listener could very well extend to some aspects of respiration (as a motor act) as well. ...
It has long been known that human breathing is altered during listening and speaking compared to rest: during speaking, inhalation depth is adjusted to the air volume required for the upcoming utterance. During listening, inhalation is temporally aligned to inhalation of the speaker. While evidence for the former is relatively strong, it is virtually absent for the latter. We address both phenomena using recordings of speech envelope and respiration in 30 participants during 14 min of speaking and listening to one's own speech. First, we show that inhalation depth is positively correlated with the total power of the speech envelope in the following utterance. Second, we provide evidence that inhalation during listening to one's own speech is significantly more likely at time points of inhalation during speaking. These findings are compatible with models that postulate alignment of internal forward models of interlocutors with the aim to facilitate communication.
... The discovery of mirror neurons 28,29 reinforced the idea that motor functions are involved in speech perception. The involvement of the motor system (or the motor and premotor cortex) has also been investigated [30][31][32][33][34][35] in the perception of speech sounds. Nevertheless, the link between speech production and perception is still poorly understood. ...
... El descubrimiento de las neuronas espejo, que se activan no solo para ejecutar ciertas acciones, sino también cuando se ven o se oyen esas acciones ejecutadas por otros (Rizzolatti et al. 1996) se relacionó desde muy pronto con la Teoría Motora. En este sentido, varios estudios con técnicas de neuroimagen han mostrado que las áreas motoras del cerebro necesarias para la producción de los sonidos están activas durante la percepción del habla (Watkins et al. 2003;Wilson et al 2004;Wilson y Iacoboni 2006) o que su estimulación interfiere con la descodificación del mensaje, especialmente en condiciones difíciles, como en presencia de ruido o distorsiones (Rogers et al. 2014;Schomers y Pulvermüller 2016;Nuttall et al. 2018). Sin embargo, también encontramos evidencias en sentido contrario: personas con lesiones en las áreas atribuidas a las neuronas espejo no tienen problemas en la percepción del habla (Rogalski et al. 2011;Stasenko et al. 2013). ...
El objetivo principal de este artículo, de carácter meramente introductorio, es mostrar el interés lingüístico de resultados obtenidos mediante las principales técnicas de neuroimagen funcional aplicadas al estudio del lenguaje, y los retos asociados al encuentro interdisciplinar entre la Lingüística y la Neurociencia. Comenzamos resumiendo los principios básicos de funcionamiento de las dos metodologías más utilizadas actualmente para estudiar la actividad del cerebro mientras realiza tareas lingüísticas: la de base electromagnética y la de base metabólica. A continuación, propondremos ejemplos de preguntas relevantes para la Lingüística que pueden encontrar respuestas en datos obtenidos mediante técnicas de neuroimagen. Concluiremos reflexionando sobre los distintos niveles de implicación de los lingüistas en el uso y avance de las técnicas de neuroimagen.
... Speech production and speech perception are frequently studied separately in research, yet the two processes have a robust, interactive theoretical link (Houde and Nagarajan 2011;Tourville and Guenther 2011;Zheng, Munhall, and Johnsrude 2010;Watkins, Strafella, and Paus 2003;Skipper, Devlin, and Lametti 2017). Models of the neurobiology of speech production universally include the sensorimotor control of speech, a mechanism by which speakers can detect errors via auditory and somatosensory feedback and subsequently correct those errors patterns of feedback perturbation elicit larger corrective responses than unpredictable ones (Lester-Smith et al. 2020), which may corroborate the link between SIS and predictability. ...
Speaking elicits a suppressed neural response when compared to listening to others' speech, a phenomenon known as speaker-induced suppression (SIS). Previous research has focused on investigating SIS at constrained levels of linguistic representation, such as the individual phoneme and word level. Here we present scalp EEG data from a dual speech perception and production task where participants read sentences aloud then listened to playback of themselves reading those sentences. Playback was separated into predictable repetition of the previous trial and unpredictable, randomized repetition of a former trial to investigate the role predictive processing plays in SIS. Concurrent EMG was recorded to control for movement artifact during speech production. In line with previous research, event-related potential analyses at the sentence level demonstrated suppression of early auditory components of the EEG for production compared to perception. To evaluate whether specific neural representations contribute to SIS (in contrast with a global gain change), we fit linear encoding models that predicted scalp EEG based on phonological features, EMG activity, and task condition. We found that phonological features were encoded similarly between production and perception. However, this similarity was only observed when controlling for movement by using the EMG response as an additional regressor. Our results suggest SIS is at the representational level a global gain change between perception and production, not the suppression of specific characteristics of the neural response. We also detail some important considerations when analyzing EEG during continuous speech production.
... The second stage is late and occurs when semantic processing has already been completed. In this situation, participants give faster responses (for example action-sentence compatibility effect, ACE; see Del Maschio et al., 2021) or show facilitation of different neurophysiological parameters elicited with different neurophysiological techniques (Watkins and Strafella, 2003;Chersi et al., 2010;de Vega et al., 2013;Klepp et al., 2017Klepp et al., , 2019. Considering that, as revealed also by the present results, a substantial motor equivalence exists between observed actions and verbally described actions (Buccino et al., 2016;Hardwick et al., 2018;Garofalo et al., 2022), one may argue that the time course of motor activity during action observation overlaps the one found during the processing of verbally described actions. ...
There is experimental evidence that the brain systems involved in action execution also play a role in action observation and understanding. Recently, it has been suggested that the sensorimotor system is also involved in language processing. Supporting results are slower response times and weaker motor-related MEG Beta band power suppression in semantic decision tasks on single action verbs labels when the stimulus and the motor response involve the same effector. Attenuated power suppression indicates decreased cortical excitability and consequent decreased readiness to act. The embodied approach forwards that the simultaneous involvement of the sensorimotor system in the processing of the linguistic content and in the planning of the response determines this language-motor interference effect. Here, in a combined behavioral and MEG study we investigated to what extent the processing of actions visually presented (i.e., pictures of actions) and verbally described (i.e., verbs in written words) share common neural mechanisms. The findings demonstrated that, whether an action is experienced visually or verbally, its processing engages the sensorimotor system in a comparable way. These results provide further support to the embodied view of semantic processing, suggesting that this process is independent from the modality of presentation of the stimulus, including language.
... The present study focuses on the process of cognition embodied in the auditory perception of emotions. Several studies have revealed that passive listening of voice signals triggered activations in motor brain regions similar to those solicited during production (Fadiga et al., 2002;Watkins et al., 2003;Wilson et al., 2004). Another study showed a facilitation of language comprehension when the primary motor areas controlling the lips or tongue were transcranially stimulated for sounds produced by either muscle, respectively (D'Ausilio et al., 2009). ...
Introduction
Emotional prosody is defined as suprasegmental and segmental changes in the human voice and related acoustic parameters that can inform the listener about the emotional state of the speaker. While the processing of emotional prosody is well represented in the literature, the mechanism of embodied cognition in emotional voice perception is very little studied. This study aimed to investigate the influence of induced bodily vibrations—through a vibrator placed close to the vocal cords—in the perception of emotional vocalizations. The main hypothesis was that induced body vibrations would constitute a potential interoceptive feedback that can influence the auditory perception of emotions. It was also expected that these effects would be greater for stimuli that are more ambiguous.
Methods
Participants were presented with emotional vocalizations expressing joy or anger which varied from low-intensity vocalizations, considered as ambiguous, to high-intensity ones, considered as non-ambiguous. Vibrations were induced simultaneously in half of the trials and expressed joy or anger congruently with the voice stimuli. Participants had to evaluate each voice stimulus using four visual analog scales (joy, anger, and surprise, sadness as control scales).
Results
A significant effect of the vibrations was observed on the three behavioral indexes—discrimination, confusion and accuracy—with vibrations confusing rather than facilitating vocal emotion processing.
Conclusion
Over all, this study brings new light on a poorly documented topic, namely the potential use of vocal cords vibrations as an interoceptive feedback allowing humans to modulate voice production and perception during social interactions.
... Observing others' manual or vocal actions activates neural mechanisms required to perform that action (Buccino et al., 2004;Fadiga et al., 1998). For vocal actions, this type of covert-or automatic-imitation occurs whenever we hear and/or see someone speak and involves activation of speech production mechanisms and associated neural substrates (Fadiga et al., 2002;Nuttall et al., 2016;Watkins et al., 2003). Covert imitation is generally referred to as automatic imitation and is measured behaviourally using the stimulus-response compatibility (SRC) paradigm for manual and for vocal actions (Brass et al., 2000;Cracco et al., 2018;Heyes, 2011;Kerzel & Bekkering, 2000, Jarick & Jones, 2009. ...
Observing someone perform an action automatically activates neural substrates associated with executing that action. This covert response, or automatic imitation , is measured behaviourally using the stimulus–response compatibility (SRC) task. In an SRC task, participants are presented with compatible and incompatible response–distractor pairings (e.g., an instruction to say “ba” paired with an audio recording of “da” as an example of an incompatible trial). Automatic imitation is measured as the difference in response times (RT) or accuracy between incompatible and compatible trials. Larger automatic imitation effects have been interpreted as a larger covert imitation response. Past results suggest that an action’s biological status affects automatic imitation: Human-produced manual actions show enhanced automatic imitation effects compared with computer-generated actions. Per the integrated theory for language comprehension and production, action observation triggers a simulation process to recognize and interpret observed speech actions involving covert imitation. Human-generated actions are predicted to result in increased automatic imitation because the simulation process is predicted to engage more for actions produced by a speaker who is more similar to the listener. We conducted an online SRC task that presented participants with human and computer-generated speech stimuli to test this prediction. Participants responded faster to compatible than incompatible trials, showing an overall automatic imitation effect. Yet the human-generated and computer-generated vocal stimuli evoked similar automatic imitation effects. These results suggest that computer-generated speech stimuli evoke the same covert imitative response as human stimuli, thus rejecting predictions from the integrated theory of language comprehension and production.
... While the original account has demonstrated alignment at every linguistic level (Pickering and Garrod, 2004) this concept also extends to temporal features in conversation such as speech rate, inter-speaker pause duration, and turn duration (Ostrand and Chodroff, 2021). Furthermore, during listening, brain areas associated with speech production are activated and likely improve comprehension (Möttönen et al., 2013;Pickering and Garrod, 2013;Watkins et al., 2003). Indeed, activity in listeners' motor areas is at least partly temporally aligned with activity in the speaker's motor system (Keitel et al., 2018;Park et al., 2018Park et al., , 2015. ...
It has long been known that human breathing is altered during listening and speaking compared to rest. Theoretical models of human communication suggest two distinct phenomena during speaking and listening: During speaking, inhalation depth is adjusted to the air volume required for the upcoming utterance. During listening, inhalation is temporally aligned to inhalation of the speaker. While evidence for the former is relatively strong, it is virtually absent for the latter. We address both questions using recordings of speech envelope and respiration in 30 participants during 14 minutes of speaking and listening. We extend existing evidence for the first phenomenon by using the speech envelope to show that inhalation depth is positively correlated with the total power of the speech envelope in the following utterance. Pertaining to the second phenomenon, we provide first evidence that inhalation during listening to your own speech is significantly more likely at time points of inhalation during speaking. These findings are compatible with models that postulate alignment of internal forward models of interlocutors with the aim to facilitate communication.
... Over the last twenty years, a large number of experimental data provided by neuroimaging tools have demonstrated the existence of sensory-motor links in the human brain during speech perception tasks (e.g. Benson et al., 2001;Fadiga et al., 2002;Pulvermüller et al., 2006;Watkins et al., 2003; see a review in Skipper et al., 2017), and confirmed that these links do have a potentially causal role in speech perception (d'Ausilio et al., 2009(d'Ausilio et al., , 2011Möttönen et al., 2013Möttönen et al., , 2014Sato et al., 2009Sato et al., , 2011; see a review in Schomers & Pulvermüller, 2016; and a caveat on the importance of this causal role in Stokes et al., 2019). A striking finding, however, is that motor areas are more activated in noisy (Binder et al., 2004;Du et al., 2014;Zekveld et al., 2006) or in atypical listening conditions (Callan et al., 2004(Callan et al., , 2014Wilson & Iacoboni, 2006), and that their modulatory role in speech perception is more apparent for ambiguous or noisy stimuli (d'Ausilio et al., 2009(d'Ausilio et al., , 2011Sato et al., 2011). ...
A computational model of speech perception, COSMO (Laurent et al., 2017), predicts that speech sounds should evoke both auditory representations in temporal areas and motor representations mainly in inferior frontal areas. Importantly, the model also predicts that auditory representations should be narrower, i.e. more focused on typical stimuli, than motor representations which would be more tolerant of atypical stimuli. Based on these assumptions, in a repetition-suppression study with functional magnetic resonance imaging data, we show that a sequence of 4 identical vowel sounds produces lower cortical activity (i.e. larger suppression effects) than if the last sound in the sequence is slightly varied. Crucially, temporal regions display an increase in cortical activity even for small acoustic variations, indicating a release of the suppression effect even for stimuli acoustically close to the first stimulus. In contrast, inferior frontal, premotor, insular and cerebellar regions show a release of suppression for larger acoustic variations. This “auditory-narrow motor-wide” pattern for vowel stimuli adds to a number of similar findings on consonant stimuli, confirming that the selectivity of speech sound representations in temporal auditory areas is narrower than in frontal motor areas in the human cortex.
... For instance, listening to music modulates the excitability of M1 areas mapping for specific groups of muscles 70 ; listening to speech increases the excitability of the left (language dominant) M1, with greater impact on regions subserving muscles recruited during speech 71 . A tight connection between A1 and M1 has been shown in previous studies 21,[72][73][74] . Moreover, an fMRI study has unveiled a WN-related connectivity increase between subcortical dopaminergic nuclei and right superior temporal sulcus 34 , potentially hinting towards the influence of WN on motor planning. ...
Auditory white noise (WN) is widely used in neuroscience to mask unwanted environmental noise and cues, e.g. TMS clicks. However, to date there is no research on the influence of WN on corticospinal excitability and potentially associated sensorimotor integration itself. Here we tested the hypothesis, if WN induces M1 excitability changes and improves sensorimotor performance. M1 excitability (spTMS, SICI, ICF, I/O curve) and sensorimotor reaction‑time performance were quantified before, during and after WN stimulation in a set of experiments performed in a cohort of 61 healthy subjects.
WN enhanced M1 corticospinal excitability, not just during exposure, but also during silence periods intermingled with WN, and up to several minutes after the end of exposure. Two independent behavioural experiments highlighted that WN improved multimodal sensorimotor performance. The enduring excitability modulation combined with the effects on behaviour suggest that WN might induce neural plasticity. WN is thus a relevant modulator of corticospinal function; its neurobiological effects should not be neglected and could in fact be exploited in research application
... As a support to this theoretical claim, there is now ample empirical evidence which has demonstrated that perceiving speech involves neural activity of the motor system. For example, Watkins et al. (2003) found that both while listening to speech and while seeing speech-related lip movements, the participants showed enhanced muscle activity in the tongue. The motor cortex is also involved in visual perception of written signs (Longcamp et al. 2006). ...
In this paper we make a proposal that writing modality (pen-and-paper versus computer-based writing can be conceptualized as a cognitive task complexity factor. To lay ground for this theoretical proposal, we first review previous adaptations of cognitive task-based models to second language (L2) writing. We then compare pen-and-paper and computer-based writing modalities in terms of their general characteristics, outline the main tenets of multidisciplinary theoretical models which attribute learning and performance-related importance to writing modality, and review the available empirical evidence. From this we draw theoretical and empirical justification for our conceptualization of writing modality as a task complexity dimension. After outlining our conceptual view, we proceed with the review of the methods which could be used to independently assess cognitive load in paper and computer-written L2 tasks. In the conclusion, implications and suggestions for future research are provided.
... The left IFG is associated with both phonological encoding as part of the dorsal cortical language pathway and phonological processing (Burton et al., 2000;Schwartz et al., 2012) as well as semantic encoding and processing (Binder et al., 2009;Demb et al., 1995). The PCG is thought to be involved in articulatory planning and execution, as well as speech perception (Pulvermüller et al., 2006;Watkins & Paus, 2004;Watkins et al., 2003). Improvement was also positively correlated with pre-therapy naming and sentence comprehension scores. ...
Background
A variety of therapies for aphasia can be found in the current literature. However, the questions of which changes in the brain are most linked with improvement of language abilities, and how alterations in neural activation are affected by different approaches to therapy, require further exploration. This systematic review therefore aimed to investigate the effects of different therapies on both language deficits and brain function and structure.
Methods & Procedures
Studies utilising neuroimaging and language testing before and after neuroscience-based treatment were identified using a 2-stage analysis. From an initial 506 citations, 483 were excluded, leaving 23 studies to be included in the review.
Outcomes & Results
The resulting studies covered therapies ranging in approach from targeting specific stages of language processing, to employing alternative modalities of communication, to facilitating activation of specific regions of the brain. Many studies found changes in both hemispheres following treatment, particularly those with datasets including mild deficits.
Conclusions
Overall, this review shows that manifold changes in the brain may occur, stemming from therapy and improvement in language abilities, although which changes are most important in facilitating improvement for participants with different specific profiles of damage and language deficit remains unclear.
... Neurons found in the brain's central processing unit activate when we perform an action or observe someone else perform an action. For instance, when we watch or even hear someone play an instrument, neurons associated with the muscles required to perform that action are activated (Keysers et al., 2003;Kohler et al., 2002;Rizzolatti & Craighero, 2004;Watkins, Strafella, & Paus, 2003). Altogether, this suggests that a child's experience of listening to music is a far more active experience than it initially appears. ...
Musical care has multiple roles in the nurturing of a child. Music can have a powerful influence on children’s emotions, behaviour, and cognition. The chapter focuses on the ages 5 to 12 years: a period of childhood that typically encompasses rapid and vast developmental change. Drawing together research and clinical perspectives from the authors’ disciplines of music psychology, music education, and music therapy, the chapter frames itself around the three main areas of childhood development: cognitive, physiological/physical, and social-emotional. Research on the cognitive outcomes of musical care for children range from improved spatial abilities and IQ to enhanced memory and verbal intelligence. The physiological outcomes include pain reduction, relaxation, and reduced secretion of the stress hormone cortisol. The physical outcomes include improved gross and fine motor skills, temporal coordination, strength, and greater ability to synchronize with others. Social-emotional outcomes ranges from changes in intrapersonal capacities such as self-esteem, confidence, emotional regulation, and stability to changes in interpersonal capacities, including empathy, social relationships and bonding, shared attention, and communication skills. The chapter discusses the various methodologies used in research studies on music and children and suggests ways towards interdisciplinary collaboration. Then further research directions for musical care in childhood are presented. In conclusion, the authors argue that music is an act of caregiving that can influence the quality of a child’s development and therefore offers one way to nurture children’s cognitive, physical, and social-emotional capacities in preparation for the next stage of life.
... The first challenge, based mostly on studies of phoneme perception using tasks such as syllable discrimination, disputes the view that sensory cortex alone is sufficient for perceptual processes, as putatively perceptual speech tasks have been found to invoke the involvement of various levels and subsystems of motor cortex (Pulvermüller et al., 2006;Pulvermüller, Hauk, Nikulin, & Ilmoniemi, 2005;Wilson, Saygin, Sereno, & Iacoboni, 2004;Watkins, Strafella, & Paus, 2003;Rizzolatti & Arbib, 1998). This view was first proposed in the form of the motor theory of speech perception (Liberman, Cooper, Shankweiler, & Studdert-Kennedy, 1967;Liberman, 1957) and indirectly linked the process to motor cortex. ...
The neural basis of language has been studied for centuries, yet the networks critically involved in simply identifying or understanding a spoken word remain elusive. Several functional–anatomical models of critical neural substrates of receptive speech have been proposed, including (1) auditory-related regions in the left mid-posterior superior temporal lobe, (2) motor-related regions in the left frontal lobe (in normal and/or noisy conditions), (3) the left anterior superior temporal lobe, or (4) bilateral mid-posterior superior temporal areas. One difficulty in comparing these models is that they often focus on different aspects of the sound-to-meaning pathway and are supported by different types of stimuli and tasks. Two auditory tasks that are typically used in separate studies—syllable discrimination and word comprehension—often yield different conclusions. We assessed syllable discrimination (words and nonwords) and word comprehension (clear speech and with a noise masker) in 158 individuals with focal brain damage: left (n = 113) or right (n = 19) hemisphere stroke, left (n = 18) or right (n = 8) anterior temporal lobectomy, and 26 neurologically intact controls. Discrimination and comprehension tasks are doubly dissociable both behaviorally and neurologically. In support of a bilateral model, clear speech comprehension was near ceiling in 95% of left stroke cases and right temporal damage impaired syllable discrimination. Lesion-symptom mapping analyses for the syllable discrimination and noisy word comprehension tasks each implicated most of the left superior temporal gyrus. Comprehension but not discrimination tasks also implicated the left pMTG, whereas discrimination but not comprehension tasks also implicated more dorsal sensorimotor regions in posterior perisylvian cortex.
... Previous research has shown cortical activation in frontal/motor speech production areas during speech perception tasks (e.g. [62][63][64][65] ) and audio-visual speech disambiguation 66 , particularly when using noisy/degraded auditory stimuli [67][68][69][70] . The lateral inferior pre-CG cluster in the current study overlaps with the somatosensory lip and tongue representation 71 . ...
While children are able to name letters fairly quickly, the automatisation of letter-speech sound mappings continues over the first years of reading development. In the current longitudinal fMRI study, we explored developmental changes in cortical responses to letters and speech sounds across 3 yearly measurements in a sample of 18 8–11 year old children. We employed a text-based recalibration paradigm in which combined exposure to text and ambiguous speech sounds shifts participants’ later perception of the ambiguous sounds towards the text. Our results showed that activity of the left superior temporal and lateral inferior precentral gyri followed a non-linear developmental pattern across the measurement sessions. This pattern is reminiscent of previously reported inverted-u-shape developmental trajectories in children’s visual cortical responses to text. Our findings suggest that the processing of letters and speech sounds involves non-linear changes in the brain’s spoken language network possibly related to progressive automatisation of reading skills.
... Such observations tend to support the idea of a coupling of production and perception in voice recognition/identification. In fact, it is well established that hearing, or hearing and seeing someone speak, activates many of the cortical regions that are involved in producing speech (Watkins, Strafella & Paus, 2003;Wilson, Saygin, Sereno & Iacoboni, 2004). In sum, speech production and perception both entail activation of coupled, sensorimotor representations that may extend to representations of voices in their dynamic aspects. ...
La capacité humaine de reconnaitre et d’identifier de nombreux individus uniquement grâce à leur voix est unique et peut s’avérer cruciale pour certaines enquêtes. La méconnaissance de cette capacité jette cependant de l’ombre sur les applications dites « légales » de la phonétique. Le travail de thèse présenté ici a comme objectif principal de mieux définir les différents processus liés au traitement des voix dans le cerveau et les paramètres affectant ce traitement. Dans une première expérience, les potentiels évoqués (PÉs) ont été utilisés pour démontrer que les voix intimement familières sont traitées différemment des voix inconnues, même si ces dernières sont fréquemment répétées. Cette expérience a également permis de mieux définir les notions de reconnaissance et d’identification de la voix et les processus qui leur sont associés (respectivement les composantes P2 et LPC). Aussi, une distinction importante entre la reconnaissance de voix intimement familières (P2) et inconnues, mais répétées (N250) a été observée. En plus d’apporter des clarifications terminologiques plus-que-nécessaires, cette première étude est la première à distinguer clairement la reconnaissance et l’identification de locuteurs en termes de PÉs. Cette contribution est majeure, tout particulièrement en ce qui a trait aux applications légales qu’elle recèle. Une seconde expérience s’est concentrée sur l’effet des modalités d’apprentissage sur l’identification de voix apprises. Plus spécifiquement, les PÉs ont été analysés suite à la présentation de voix apprises à l’aide des modalités auditive, audiovisuelle et audiovisuelle interactive. Si les mêmes composantes (P2 et LPC) ont été observées pour les trois conditions d’apprentissage, l’étendue de ces réponses variait. L’analyse des composantes impliquées a révélé un « effet d’ombrage du visage » (face overshadowing effect, FOE) tel qu’illustré par une réponse atténuée suite à la présentation de voix apprise à l’aide d’information audiovisuelle par rapport celles apprises avec dans la condition audio seulement. La simulation d’interaction à l’apprentissage à quant à elle provoqué une réponse plus importante sur la LPC en comparaison avec la condition audiovisuelle passive. De manière générale, les données rapportées dans les expériences 1 et 2 sont congruentes et indiquent que la P2 et la LPC sont des marqueurs fiables des processus de reconnaissance et d’identification de locuteurs. Les implications fondamentales et en phonétique légale seront discutées.
The human ability to recognize and identify speakers by their voices is unique and can be critical in criminal investigations. However, the lack of knowledge on the working of this capacity overshadows its application in the field of “forensic phonetics”. The main objective of this thesis is to characterize the processing of voices in the human brain and the parameters that influence it. In a first experiment, event related potentials (ERPs) were used to establish that intimately familiar voices are processed differently from unknown voices, even when the latter are repeated. This experiment also served to establish a clear distinction between neural components of speaker recognition and identification supported by corresponding ERP components (respectively the P2 and the LPC). An essential contrast between the processes underlying the recognition of intimately familiar voices (P2) and that of unknown but previously heard voices (N250) was also observed. In addition to clarifying the terminology of voice processing, the first study in this thesis is the first to unambiguously distinguish between speaker recognition and identification in terms of ERPs. This contribution is major, especially when it comes to applications of voice processing in forensic phonetics. A second experiment focused more specifically on the effects of learning modalities on later speaker identification. ERPs to trained voices were analysed along with behavioral responses of speaker identification following a learning phase where participants were trained on voices in three modalities : audio only, audiovisual and audiovisual interactive. Although the ERP responses for the trained voices showed effects on the same components (P2 and LPC) across the three training conditions, the range of these responses varied. The analysis of these components first revealed a face overshadowing effect (FOE) resulting in an impaired encoding of voice information. This well documented effect resulted in a smaller LPC for the audiovisual condition compared to the audio only condition. However, effects of the audiovisual interactive condition appeared to minimize this FOE when compared to the passive audiovisual condition. Overall, the data presented in both experiments is generally congruent and indicate that the P2 and the LPC are reliable electrophysiological markers of speaker recognition and identification. The implications of these findings for current voice processing models and for the field of forensic phonetics are discussed.
... The first stage that occurs very early after stimulus presentation is possibly crucial for understanding and manifests itself in the slowing down of motor responses behaviorally (Boulenger et al., 2006;Buccino et al., 2005;Dalla Volta et al., 2009;Marino et al., 2014;Sato et al., 2008;de Vega et al., 2013), a decrease of MEPs amplitude, as revealed by TMS, and a weaker decrease of beta rhythm as revealed by MEG (Buccino et al., 2005;Klepp et al., 2015). The second stage is delayed, occurs when semantic processing has already been completed, and manifests itself in faster responses (for example in ACE, see Glenberg & Kaschak, 2002) and a facilitation of motor activity as revealed by different neurophysiological techniques Klepp, van Dijk, Niccolai, Schnitzler, & Biermann-Ruben, 2019;Pulvermüller et al., 2001;Watkins, Strafella, & Paus, 2003;see also, Chersi, Thill, Ziemke, & Borghi, 2010;de Vega et al., 2013). Considering all that, one may argue that also during action observation, a similar time course of motor activity occurs. ...
It is well-accepted that processing observed actions involves at some extent the same neural mechanisms responsible for action execution. More recently, it has been forwarded that also the processing of verbs expressing a specific motor content is subserved by the neural mechanisms allowing individuals to perform the content expressed by that linguistic material. This view is also known as embodiment and contrasts with a more classical approach to language processing that considers it as amodal. In the present study, we used a go/no-go paradigm, in which participants were requested to respond to real words and pictures and refrain from responding when presented stimuli were pseudowords and scrambled images. Real stimuli included pictures depicting hand- and foot-related actions and verbs expressing hand- and foot-related actions. We, therefore, directly compared the modulation of hand motor responses during the observation of actions and the presentation of verbs, expressing actions in the same category. The results have shown that participants gave slower hand motor responses during the observation of hand actions and the processing of hand-related verbs as than observed foot actions and related verbs. These findings support embodiment showing that whatever the modality of presentation (observed action or verb), the modulation of hand motor responses was similar, thus suggesting that processing seen actions and related verbs shares common mechanisms most likely involving the motor system and the underlying motor experience.
... La technique de stimulation magnétique transcrânienne à impulsion unique (single pulse TMS) a également permis de mettre en évidence un mécanisme de "résonance motrice" (voir Figure I.7), correspondant à une augmentation de l'excitabilité des neurones du cortex moteur primaire reliés aux muscles orofaciaux labiaux et linguaux lors de la perception de la parole (Sundara, Namasivayam et Chen, 2001;Fadiga et al., 2002;Watkins, Strafella et Paus, 2003;Watkins et Paus, 2004;Roy et al., 2008;Sato et al., 2010; pour une revue de l'application de la technique de TMS lors de l'observation d'action, voir Fadiga, Craighero et Olivier, 2005). De plus, Watkins et Paus (2004), en utilisant conjointement les techniques de TMS et de tomographie par émission de positons (PET) ont montré que cette excitabilité du cortex moteur primaire labial lors de la perception de la parole était corrélée avec l'activité du gyrus frontal inférieur postérieur. ...
Speech is built on a set of correspondences between sensory and articulatory representations, especially during the acquisition of language in the early years of life. Using functional magnetic resonance imaging, the primary goal of our work was to determine, in adults, a possible functional coupling of French vowel perception and production systems, as elementary speech units. In parallel, our work should help to clarify the brain structures related to the orofacial motor control of simple supralaryngeal movements and to determine a possible causal contribution of sensory and motor regions during speech perception. Our work highlights the involvement of sensory and motor areas when performing orofacial gestures and during vowel production and perception. Adaptive effects of these motor, auditory and somatosensory regions during repeated orofacial movements and in vowel perception and production suggest the existence of common adaptive mechanisms involved in the online control of perceived and produced speech gestures. Finally, we demonstrated a causal and functional role of the sensorimotor regions of the dorsal pathway in speech categorization. Taken together, our results emphasize the distributed sensorimotor nature of cerebral representations of speech units.
... Within the context of embodied cognition, some proposals argue that phonemic representations are partly rooted, in the sensorimotor experience, with the phonemic units being partially driven by the internal simulation from action to perception (Pulvermüller et al., 2005;Schwartz et al., 2012). The strength of this perception-action coupling is also highlighted by various neurophysiological studies (Fadiga et al., 1995;Watkins et al., 2003, Scerrati et al., 2015, which show that pre-activation of visual and auditory inputs can be facilitated by the prior perception of a linguistic stimulus. Moreover, this functional perception-action coupling, as underpinned by the mirror neuron system (Rizzolatti et al., 2001(Rizzolatti et al., , 2002, is established early in infancy and is the basis for the development of sensorimotor, cognitive, and social representations (Assaiante et al., 2014, see also Wilson and Knoblich, 2005). ...
Sensorimotor disorders have been frequently reported in children and adults with dyslexia over the past 30 years. The present study aimed to determine the impact of sensorimotor comorbidity risks in dyslexia by investigating the functional links between phonological and sensorimotor representations in young dyslexic adults. Using 52 dyslexic participants and 58 normo-readers, we investigated whether the underlying phonological deficit, which is reported in the literature, was associated with a general impairment of sensorimotor representations of articulatory and bodily actions. Internal action representations were explored through motor imagery tasks, consisting of measuring and comparing the durations of performed or imagined actions chosen from their current repertoire of daily life activities. To detect sensorimotor deficits, all participants completed the extended version of the M-ABC 2, as a reference test. We found sensorimotor impairments in 27% of the young adult dyslexics, then considered as sensorimotor comorbid, as opposed to much less in the normo-reader group (5%). While motor slowdown, reflecting motor difficulty, was present in all dyslexic adults, motor imagery performance was impacted only in the specific dyslexic subgroup with sensorimotor impairments. Moreover, in contrast with slowness, only the comorbid subgroup showed an increased variability in execution durations. The present study highlights the importance of the quality of perception-action coupling, questions the relevance of investigating sensorimotor impairment profiles beyond phonological deficits and provides new arguments supporting the perspective of multiple deficits approaches in dyslexia.
... Irregular target words were produced slower in both conditions, i.e., an entrainment effect was not evident for these words. In a more general sense, our results confirm a close intertwining of language perception and production processes in neurotypical speakers [93]. ...
Citation: Aichert, I.; Lehner, K.; Falk, S.; Späth, M.; Franke, M.; Ziegler, W. Abstract: In the present study, we investigated if individuals with neurogenic speech sound impairments of three types, Parkinson's dysarthria, apraxia of speech, and aphasic phonological impairment, accommodate their speech to the natural speech rhythm of an auditory model, and if so, whether the effect is more significant after hearing metrically regular sentences as compared to those with an irregular pattern. This question builds on theories of rhythmic entrainment, assuming that sensorimotor predictions of upcoming events allow humans to synchronize their actions with an external rhythm. To investigate entrainment effects, we conducted a sentence completion task relating participants' response latencies to the spoken rhythm of the prime heard immediately before. A further research question was if the perceived rhythm interacts with the rhythm of the participants' own productions, i.e., the trochaic or iambic stress pattern of disyllabic target words. For a control group of healthy speakers, our study revealed evidence for entrainment when trochaic target words were preceded by regularly stressed prime sentences. Persons with Parkinson's dysarthria showed a pattern similar to that of the healthy individuals. For the patient groups with apraxia of speech and with phonological impairment, considerably longer response latencies with differing patterns were observed. Trochaic target words were initiated with significantly shorter latencies, whereas the metrical regularity of prime sentences had no consistent impact on response latencies and did not interact with the stress pattern of the target words to be produced. The absence of an entrainment in these patients may be explained by the more severe difficulties in initiating speech at all. We discuss the results in terms of clinical implications for diagnostics and therapy in neurogenic speech disorders.
... De nombreuses études ont avancé que le numérique et l'organisation en mode projet modifie l'activité de conception (e.g. Brassac, 2003 ;Darses, 2009 Watkins et al., 2003). D'ailleurs, la production langagière engendre l'articulation et donc l'activation de l'aire motrice que l'on remarque par la synchronisation des séquences motrices du mouvement de la bouche avec la production de gestes co-verbaux (Bernardis & Gentilucci, 2006), que l'on a appelé gesticulations dans notre étude. ...
L’activité de conception mobilise des fonctions cognitives de haut niveau largement étudiées depuis ces dernières années. Cependant, dans un souci d’améliorer toujours plus l’innovation, la créativité et de réduire les barrières de communication entre les designers et les non-designers pendant les réunions de co-conception du produit, des outils d’aide à la conception sont déployés, tous poursuivants des objectifs différents. La plateforme SPARK utilisant les propriétés de la Réalité Augmentée Spatialisée (SAR) est notamment un outil développé pour faciliter les interactions et la compréhension entre les experts et les non-experts de la conception dans les phases de revue. C’est dans ce contexte que s’inscrit ce travail de thèse où nous proposons une analyse multimodale de l’activité de co-conception dans un environnement SAR. Nous avons employé une démarche ergonomique tout au long de cette recherche en procédant à l’observation de séances de co-conception chez notre partenaire industriel puis en effectuant une expérimentation en laboratoire à plus grande échelle accompagnée de questionnaires et d’entretiens d’auto-confrontation avec les utilisateurs. Cette démarche nous a permis, d’une part, d’identifier quelle était l’influence de cette technologie sur les différentes activités cognitives et les gestes réalisés par les acteurs. Il a été montré que la technologie SAR n’a aucune influence sur les activités de conception sauf pour la génération d’idées où les résultats révèlent un nombre significativement plus important d’idées lorsqu’on utilise cet outil. Cette technologie semble également avoir une influence sur les gestes mobilisés car elle sollicite davantage la manipulation ou le pointage de l’artefact dans la scène. D’autre part, nous avons analysé les relations entre les gestes réalisés et les activités cognitives mobilisés dans le protocole verbal. Par exemple, un des résultats principaux de cette étude a montré que l’activité de simulation du contexte d’usage est significativement associée à des gestes iconiques. Les résultats de ce travail de recherche nous permettent d’avancer quelques préconisations d’usage de cette technologie dont les avantages sont avérés dans la phase de revue de la conception du produit et où la tangibilité de l’artefact est un facteur de réussite.
The human brain tracks available speech acoustics and extrapolates missing information such as the speaker's articulatory patterns. However, the extent to which articulatory reconstruction supports speech perception remains unclear. This study explores the relationship between articulatory reconstruction and task difficulty. Participants listened to sentences and performed a speech-rhyming task. Real kinematic data of the speaker's vocal tract were recorded via electromagnetic articulography (EMA) and aligned to corresponding acoustic outputs. We extracted articulatory synergies from the EMA data using Principal Component Analysis (PCA) and employed Partial Information Decomposition (PID) to separate the electroencephalographic (EEG) encoding of acoustic and articulatory features into unique, redundant, and synergistic atoms of information. We median-split sentences into easy (ES) and hard (HS) based on participants' performance and found that greater task difficulty involved greater encoding of unique articulatory information in the theta band. We conclude that fine-grained articulatory reconstruction plays a complementary role in the encoding of speech acoustics, lending further support to the claim that motor processes support speech perception.
Speech and language processing involve complex interactions between cortical areas necessary for articulatory movements and auditory perception and a range of areas through which these are connected and interact. Despite their fundamental importance, the precise mechanisms underlying these processes are not fully elucidated. We measured BOLD signals from normal hearing participants using high-field 7 Tesla fMRI with 1-mm isotropic voxel resolution. The subjects performed 2 speech perception tasks (discrimination and classification) and a speech production task during the scan. By employing univariate and multivariate pattern analyses, we identified the neural signatures associated with speech production and perception. The left precentral, premotor, and inferior frontal cortex regions showed significant activations that correlated with phoneme category variability during perceptual discrimination tasks. In addition, the perceived sound categories could be decoded from signals in a region of interest defined based on activation related to production task. The results support the hypothesis that articulatory motor networks in the left hemisphere, typically associated with speech production, may also play a critical role in the perceptual categorization of syllables. The study provides valuable insights into the intricate neural mechanisms that underlie speech processing.
Speaking elicits a suppressed neural response when compared with listening to others' speech, a phenomenon known as speaker-induced suppression (SIS). Previous research has focused on investigating SIS at constrained levels of linguistic representation, such as the individual phoneme and word level. Here, we present scalp EEG data from a dual speech perception and production task where participants read sentences aloud then listened to playback of themselves reading those sentences. Playback was separated into immediate repetition of the previous trial and randomized repetition of a former trial to investigate if forward modeling of responses during passive listening suppresses the neural response. Concurrent EMG was recorded to control for movement artifact during speech production. In line with previous research, ERP analyses at the sentence level demonstrated suppression of early auditory components of the EEG for production compared with perception. To evaluate whether linguistic abstractions (in the form of phonological feature tuning) are suppressed during speech production alongside lower-level acoustic information, we fit linear encoding models that predicted scalp EEG based on phonological features, EMG activity, and task condition. We found that phonological features were encoded similarly between production and perception. However, this similarity was only observed when controlling for movement by using the EMG response as an additional regressor. Our results suggest that SIS operates at a sensory representational level and is dissociated from higher order cognitive and linguistic processing that takes place during speech perception and production. We also detail some important considerations when analyzing EEG during continuous speech production.
Transcranial magnetic stimulation (TMS), as we use it today, was developed in the 1980s, and already in the 1990s, it was clear it would became an essential tool to study human brain functions. The present chapter focuses on the technical challenges that are specific to the use of TMS in speech and language research. A section is devoted to the co-registration of TMS and electroencephalography (EEG), highlighting the great potential as well and the challenges inherent in the integration of these two techniques. The chapter briefly revises the extensive literature using TMS in speech and language research by separating the different available protocols. In particular, trains of TMS pulses can transiently interfere with the activity of a relatively specific cortical target. This approach, often named “virtual lesion approach,” has been used to investigate the role of posterior and anterior language brain areas in receptive and production tasks, respectively. Otherwise, single or paired-pulse protocols measure neurophysiological indexes of intracortical or corticomotor excitability. In this respect, TMS research has shown a specific motor recruitment during speech perception tasks, suggesting a tight functional relationship between production and perception mechanisms. In conclusion, we provide key methodological and technical suggestions on how to best approach the design of TMS studies, based on this relatively mature field of research.Key wordsTranscranial magnetic stimulationElectroencephalographyCorticobulbar excitabilitySpeech and language perceptionSpeech and language production
Aphasia is a language disorder that often involves speech comprehension impairments affecting communication. In face-to-face settings, speech is accompanied by mouth and facial movements, but little is known about the extent to which they benefit aphasic comprehension. This study investigated the benefit of visual information accompanying speech for word comprehension in people with aphasia (PWA) and the neuroanatomic substrates of any benefit. Thirty-six PWA and 13 neurotypical matched control participants performed a picture-word verification task in which they indicated whether a picture of an animate/inanimate object matched a subsequent word produced by an actress in a video. Stimuli were either audiovisual (with visible mouth and facial movements) or auditory-only (still picture of a silhouette) with audio being clear (unedited) or degraded (6-band noise-vocoding). We found that visual speech information was more beneficial for neurotypical participants than PWA, and more beneficial for both groups when speech was degraded. A multivariate lesion-symptom mapping analysis for the degraded speech condition showed that lesions to superior temporal gyrus, underlying insula, primary and secondary somatosensory cortices, and inferior frontal gyrus were associated with reduced benefit of audiovisual compared to auditory-only speech, suggesting that the integrity of these fronto-temporo-parietal regions may facilitate cross-modal mapping. These findings provide initial insights into our understanding of the impact of audiovisual information on comprehension in aphasia and the brain regions mediating any benefit.
Auditory white noise (WN) is widely used in daily life for inducing sleep, and in neuroscience to mask unwanted environmental noise and cues. However, WN was recently reported to influence corticospinal excitability and behavioral performance. Here, we expand previous preliminary findings on the influence of WN exposure on cortical functioning, and we hypothesize that it may modulate cortical connectivity. We tested our hypothesis by performing magnetoencephalography in 20 healthy subjects. WN reduces cortical connectivity of the primary auditory and motor regions with very distant cortical areas, showing a right lateralized connectivity reduction for primary motor cortex. The present results, together with previous finding concerning WN impact on corticospinal excitability and behavioral performance, further support the role of WN as a modulator of cortical function. This suggest avoiding its unrestricted use as a masking tool, while purposely designed and controlled WN application could be exploited to harness brain function and to treat neuropsychiatric conditions.
Speech and music signals show rhythmicity in their temporal structure with slower rhythmic rates in music than in speech. Speech processing has been related to brain rhythms in the auditory and motor cortex at around 4.5 Hz, while music processing has been associated to motor cortex activity at around 2 Hz reflecting the temporal structures in speech and music. In addition, slow motor cortex brain rhythms were suggested to be central for timing in both domains. It thus remains unclear if domain-general or frequency specific mechanisms are driving speech and music processing. Additionally, for speech processing, auditory-motor cortex coupling and perception-production synchronization at 4.5 Hz have been related to enhanced auditory perception in various tasks. However, it is unknown whether this effect generalizes to synchronization and perception in music at distinct optimal rates. Using a behavioral protocol, we investigate whether (1) perception-production synchronization shows distinct optimal rates for speech and music; (2) optimal rates in perception are predicted by synchronization strength at different time scales. A perception task involving speech and music stimuli and a synchronization task using tapping and whispering were conducted at slow (~2 Hz) and fast rates (~4.5 Hz). Results revealed that synchronization was generally better at slow rates. Importantly, for slow but not for fast rates, tapping showed superior performance when compared to whispering, suggesting domain-specific rate preferences. Accordingly, synchronization performance was highly correlated across domains only at fast but not at slow rates. Altogether, perception of speech and music were optimal at different timescales, and predicted by auditory-motor synchronization strength. Our data suggests different optimal time scales for music and speech processing with partially overlapping mechanisms.
Speech perception is known to be a multimodal process, relying not only on auditory input, but also on the visual system and possibly on the motor system as well. To date there has been little work on the potential involvement of the somatosensory system in speech perception. In the current review, we identify the somatosensory system as another contributor to speech perception. First, we argue that evidence in favor of a motor contribution to speech perception can just as easily be interpreted as showing somatosensory involvement. Second, physiological and neuroanatomical evidence for auditory-somatosensory interactions across the auditory hierarchy indicates the availability of a neural infrastructure that supports somatosensory involvement in auditory processing in general. Third, there is accumulating evidence for somatosensory involvement in the context of speech specifically. In particular, tactile stimulation modifies speech perception, and speech auditory input elicits activity in somatosensory cortical areas. Moreover, speech sounds can be decoded from activity in somatosensory cortex; lesions to this region affect perception, and vowels can be identified based on somatic input alone. We suggest the somatosensory involvement in speech perception derives from the somatosensory-auditory pairing which occurs during speech production and learning. By bringing together findings from a set of studies that have not been previously linked, the current paper identifies the somatosensory system as a presently unrecognized contributor to speech perception.
Doctoral dissertation by Naeimeh Afshar, University of Pannonia, November 2022.
Speech processing entails a complex interplay between bottom-up and top-down computations. The former is reflected in the neural entrainment to the quasi-rhythmic properties of speech acoustics while the latter is supposed to guide the selection of the most relevant input subspace. Top-down signals are believed to originate mainly from motor regions, yet similar activities have been shown to tune attentional cycles also for simpler, non-speech stimuli. Here we examined whether, during speech listening, the brain reconstructs articulatory patterns associated to speech production. We measured electroencephalographic (EEG) data while participants listened to sentences during the production of which articulatory kinematics of lips, jaws and tongue were also recorded (via Electro-Magnetic Articulography, EMA). We captured the patterns of articulatory coordination through Principal Component Analysis (PCA) and used Partial Information Decomposition (PID) to identify whether the speech envelope and each of the kinematic components provided unique, synergistic and/or redundant information regarding the EEG signals. Interestingly, tongue movements contain both unique as well as synergistic information with the envelope that are encoded in the listener's brain activity. This demonstrates that during speech listening the brain retrieves highly specific and unique motor information that is never accessible through vision, thus leveraging audio-motor maps that arise most likely from the acquisition of speech production during development.
Socially situated thought and behaviour are pervasive and vitally important in human society. The social brain has become a focus of study for researchers in the neurosciences, psychology, biology and other areas of behavioural science, and it is becoming increasingly clear that social behaviour is heavily dependent on shared representations. Any social activity, from a simple conversation to a well-drilled military exercise to an exquisitely perfected dance routine, involves information sharing between the brains of those involved. This volume comprises a collection of cutting-edge essays centred on the idea of shared representations, broadly defined. Featuring contributions from established world leaders in their fields and written in a simultaneously accessible and detailed style, this is an invaluable resource for established researchers and those who are new to the field.
Hypothesis: We hypothesized that children with cochlear implants (CIs) who demonstrate cross-modal reorganization by vision also demonstrate cross-modal reorganization by somatosensation and that these processes are interrelated and impact speech perception. Background: Cross-modal reorganization, which occurs when a deprived sensory modality's cortical resources are recruited by other intact modalities, has been proposed as a source of variabil- ity underlying speech perception in deaf children with CIs. Visual and somatosensory cross-modal reorganization of auditory cortex have been documented separately in CI children, but reorganiza- tion in these modalities has not been documented within the same subjects. Our goal was to examine the relationship between cross-modal reorganization from both visual and somatosensory modalities within a single group of CI children.
Methods: We analyzed high-density electroencephalogram re- sponses to visual and somatosensory stimuli and current density reconstruction of brain activity sources. Speech perception in noise testing was performed. Current density reconstruction patterns were analyzed within the entire subject group and across groups of CI children exhibiting good versus poor speech perception. Results: Positive correlations between visual and somatosensory cross-modal reorganization suggested that neuroplasticity in dif- ferent sensory systems may be interrelated. Furthermore, CI chil- dren with good speech perception did not show recruitment of frontal or auditory cortices during visual processing, unlike CI children with poor speech perception.
Conclusion: Our results reflect changes in cortical resource allo- cation in pediatric CI users. Cross-modal recruitment of auditory and frontal cortices by vision, and cross-modal reorganization of auditory cortex by somatosensation, may underlie variability in speech and language outcomes in CI children.
It has long been known that listening to speech activates inferior frontal (pre-)motor regions in addition to a more dorsal premotor site (dPM). Recent work shows that dPM, located adjacent to laryngeal motor cortex, responds to low-level acoustic speech cues including vocal pitch, and the speech envelope, in addition to higher-level cues such as phoneme categories. An emerging hypothesis is that dPM is part of a general auditory-guided laryngeal control circuit that plays a role in producing speech and other voluntary auditory–vocal behaviors. We recently reported a study in which dPM responded to vocal pitch during a degraded speech recognition task, but only when speech was rated as unintelligible; dPM was more robustly modulated by the categorical difference between intelligible and unintelligible speech. Contrary to the general auditory–vocal hypothesis, this suggests intelligible speech is the primary driver of dPM. However, the same pattern of results was observed in pitch-sensitive auditory cortex. Crucially, vocal pitch was not relevant to the intelligibility judgment task, which may have facilitated processing of phonetic information at the expense of vocal pitch cues. The present fMRI study (n = 25) tests the hypothesis that, for a multitalker task that emphasizes pitch for talker segregation, left dPM and pitch-sensitive auditory regions will respond to vocal pitch regardless of overall speech intelligibility. This would suggest that pitch processing is indeed a primary concern of this circuit, apparent during perception only when the task demands it. Spectrotemporal modulation distortion was used to independently modulate vocal pitch and phonetic content in two-talker (male/female) utterances across two conditions (Competing, Unison), only one of which required pitch-based segregation (Competing). A Bayesian hierarchical drift-diffusion model was used to predict speech recognition performance from patterns of spectrotemporal distortion imposed on each trial. The model's drift rate parameter, a d′-like measure of performance, was strongly associated with vocal pitch for Competing but not Unison. Using a second Bayesian hierarchical model, we identified regions where behaviorally relevant acoustic features were related to fMRI activation in dPM. We regressed the hierarchical drift-diffusion model's posterior predictions of trial-wise drift rate, reflecting the relative presence or absence of behaviorally relevant acoustic features from trial to trial, against trial-wise activation amplitude. A significant positive association with overall drift rate, reflecting vocal pitch and phonetic cues related to overall intelligibility, was observed in left dPM and bilateral auditory cortex in both conditions. A significant positive association with “pitch-restricted” drift rate, reflecting only the relative presence or absence of behaviorally relevant pitch cues, regardless of the presence or absence of phonetic content (intelligibility), was observed in left dPM, but only in the Competing condition. Interestingly, the same effect was observed in bilateral auditory cortex but in both conditions. A post hoc mediation analysis ruled out the possibility that decision load was responsible for the observed pitch effects. These findings suggest that processing of vocal pitch is a primary concern of the auditory-cortex–dPM circuit, although during perception core pitch, processing is carried out by auditory cortex with a potential modulatory influence from dPM.
Successful speech understanding relies not only on the auditory pathway, but on cognitive processes that act on incoming sensory information. One area in which the importance of cognitive factors is particularly striking during speech comprehension is when the acoustic signal is made more challenging, which might happen due to background noise, talker characteristics, or hearing loss. This chapter focuses on the interaction between hearing and cognition in hearing loss in older adults. The chapter begins with a review of common age-related changes in hearing and cognition, followed by summary evidence from pupillometric, behavioral, and neuroimaging paradigms that elucidate the interplay between hearing and cognition. Across a variety of experimental paradigms, there is compelling evidence that when listeners process acoustically challenging speech, additional cognitive effort is required compared to acoustically clear speech. This increase in cognitive effort is associated with specific brain networks, with the clearest evidence implicating cingulo-opercular and executive attention networks. Individual differences in hearing and cognitive ability thus determine the cognitive demand faced by a particular listener, and the cognitive and neural resources needed to aid in speech perception.KeywordsListening effortBackground noiseSpeech perceptionCognitive agingSentence comprehensionNeuroimagingCingulo-opercular networkExecutive attentionPupillometryfMRI
Motor areas for speech production activate during speech perception. Such activation may assist speech perception in challenging listening conditions. It is not known how ageing affects the recruitment of articulatory motor cortex during active speech perception. This study aimed to determine the effect of ageing on recruitment of speech motor cortex during speech perception.
Single-pulse Transcranial Magnetic Stimulation (TMS) was applied to the lip area of left primary motor cortex (M1) to elicit lip Motor Evoked Potentials (MEPs). The M1 hand area was tested as a control site. TMS was applied whilst participants perceived syllables presented with noise (−10, 0, +10 dB SNRs) and without noise (clear). Participants detected and counted syllables throughout MEP recording. Twenty younger adult subjects (aged 18–25) and twenty older adult subjects (aged 65–80) participated in this study.
Results indicated a significant interaction between age and noise condition in the syllable task. Specifically, older adults significantly misidentified syllables in the 0 dB SNR condition, and missed the syllables in the −10 dB SNR condition, relative to the clear condition. There were no differences between conditions for younger adults. There was a significant main effect of noise level on lip MEPs. Lip MEPs were unexpectedly inhibited in the 0 dB SNR condition relative to clear condition. There was no interaction between age group and noise condition. There was no main effect of noise or age group on control hand MEPs. These data suggest that speech-induced facilitation in articulatory motor cortex is abolished when performing a challenging secondary task, irrespective of age.
presents preliminary evidence concerning the cerebral localization of lip-reading in hearing people (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Neurons of the rostral part of inferior premotor cortex of the monkey discharge during goal-directed hand movements such as grasping, holding, and tearing. We report here that many of these neurons become active also when the monkey observes specific, meaningful hand movements performed by the experimenters. The effective experimenters' movements include among others placing or retrieving a piece of food from a table, grasping food from another experimenter's hand, and manipulating objects. There is always a clear link between the effective observed movement and that executed by the monkey and, often, only movements of the experimenter identical to those controlled by a given neuron are able to activate it. These findings indicate that premotor neurons can retrieve movements not only on the basis of stimulus characteristics, as previously described, but also on the basis of the meaning of the observed actions.
1. We stimulated the motor cortex of normal subjects (transcranial magnetic stimulation) while they 1) observed an experimenter grasping 3D-objects, 2) looked at the same 3D-objects, 3) observed an experimenter tracing geometrical figures in the air with his arm, and 4) detected the dimming of a light. Motor evoked potentials (MEPs) were recorded from hand muscles. 2. We found that MEPs significantly increased during the conditions in which subjects observed movements. The MEP pattern reflected the pattern of muscle activity recorded when the subjects executed the observed actions. 3. We conclude that in humans there is a system matching action observation and execution. This system resembles the one recently described in the monkey.
To investigate mechanisms of audio-vocal interactions in the human brain, we studied the effect of speech output on modulation of neuronal activity in the auditory cortex. The modulation was assessed indirectly by measuring changes in cerebral blood flow (CBF) during unvoiced speech (whispering). Using positron emission tomography (PET), CBF was measured in eight volunteers as they uttered syllables at each of seven rates (30, 50, 70, 90, 110, 130 or 150/min) during each of the seven 60-s PET scans. Low-intensity white noise was used throughout scanning to mask auditory input contingent on the whispering. We found that, as a function of the increasing syllable rate, CBF increased in the left primary face area, the upper pons, the left planum temporale and the left posterior perisylvian cortex. The latter two regions contain secondary auditory cortex and previously have been implicated in the processing of speech sounds. We conclude that, in the absence of speech-contingent auditory input, the modulation of CBF in the auditory cortex is mediated by motor-to-sensory discharges. As such, it extends our previous findings of oculomotor corollary discharges to the audio-vocal domain.
Lateralization of perception of various facial attributes (age, attractiveness, gender, lip-reading and expression) was studied using chimaeric faces in which the sides of the face differed along one dimension (e.g. the left side was male and the right side female). Computer graphics were used to eliminate naturally occurring physical asymmetries (e.g. those present in the mouth during speech and spontaneous smiles) and obvious vertical mid-line joins in the photo-realistic chimaeric stimuli. Following previous studies, we found that subjects' judgements of gender and expression were influenced more by the left than the right side of the face (viewer's perspective). This left of face stimulus bias extended to judgements about facial attractiveness and facial age. This was not true of lip-reading stimuli; for these stimuli subjects were influenced more by the right than the left side of the face. Thus using free fixation, it appears possible to demonstrate in normal subjects that brain processes underlying judgements of facial speech display different lateralization from the judgements of other facial dimensions.
The monkey premotor cortex contains neurons that discharge during action execution and during observation of actions made by others. Transcranial magnetic stimulation experiments suggest that a similar observation/execution matching system also is present in humans. We recorded neuromagnetic oscillatory activity of the human precentral cortex from 10 healthy volunteers while (i) they had no task to perform, (ii) they were manipulating a small object, and (iii) they were observing another individual performing the same task. The left and right median nerves were stimulated alternately (interstimulus interval, 1.5 s) at intensities exceeding motor threshold, and the poststimulus rebound of the rolandic 15- to 25-Hz activity was quantified. In agreement with previous studies, the rebound was strongly suppressed bilaterally during object manipulation. Most interestingly, the rebound also was significantly diminished during action observation (31-46% of the suppression during object manipulation). Control experiments, in which subjects were instructed to observe stationary or moving stimuli, confirmed the specificity of the suppression effect. Because the recorded 15- to 25-Hz activity is known to originate mainly in the precentral motor cortex, we concluded that the human primary motor cortex is activated during observation as well as execution of motor tasks. These findings have implications for a better understanding of the machinery underlying action recognition in humans.
There is described a 60-channel EEG acquisition system designed for the recording of scalp-potential distributions starting just 2.5 ms after individual transcranial magnetic stimulation (TMS) pulses. The amplifier comprises gain-control and sample-and-hold circuits to prevent large artefacts from magnetically induced voltages in the leads. The maximum amplitude of the stimulus artefact during the 2.5 ms gating period is 1.7 microV, and 5 ms after the TMS pulse it is only 0.9 microV. It is also shown that mechanical forces to the electrodes under the stimulator coil are a potential source of artefacts, even though, with chlorided silver wire and Ag/AgCl-pellet electrodes, the artefact is smaller than 1 microV. The TMS-compatible multichannel EEG system makes it possible to locate TMS-evoked electric activity in the brain.
In a previous study we used functional magnetic resonance imaging (fMRI) to demonstrate activation in auditory cortex during silent speechreading. Since image acquisition during fMRI generates acoustic noise, this pattern of activation could have reflected an interaction between background scanner noise and the visual lip-read stimuli. In this study we employed an event-related fMRI design which allowed us to measure activation during speechreading in the absence of acoustic scanner noise. In the experimental condition, hearing subjects were required to speechread random numbers from a silent speaker. In the control condition subjects watched a static image of the same speaker with mouth closed and were required to subvocally count an intermittent visual cue. A single volume of images was collected to coincide with the estimated peak of the blood oxygen level dependent (BOLD) response to these stimuli across multiple baseline and experimental trials. Silent speechreading led to greater activation in lateral temporal cortex relative to the control condition. This indicates that activation of auditory areas during silent speechreading is not a function of acoustic scanner noise and confirms that silent speechreading engages similar regions of auditory cortex as listening to speech.
Does the lateral temporal cortex require acoustic exposure in order to become specialized for speech processing? Six hearing participants and six congenitally deaf participants, all with spoken English as their first langugage, were scanned using functional magnetic resonance imaging while performing a simple speech-reading task. Focal activation of the left lateral temporal cortex was significantly reduced in the deaf group compared with the hearing group. Activation within this region was present in individual deaf participants, but varied in location from person to person. Early acoustic experience may be required for regions within the left temporal cortex in order to develop into a coherent network with subareas devoted to specific speech analysis functions.
The precise neural mechanisms underlying speech perception are still to a large extent unknown. The most accepted view is that speech perception depends on auditory-cognitive mechanisms specifically devoted to the analysis of speech sounds. An alternative view is that, crucial for speech perception, it is the activation of the articulatory (motor) gestures that generate these sounds. The listener understands the speaker when his/her articulatory gestures are activated (motor theory of speech perception). Here, by using transcranial magnetic stimulation (TMS), we demonstrate that, during speech listening, there is an increase of motor-evoked potentials recorded from the listeners' tongue muscles when the presented words strongly involve, when pronounced, tongue movements. Although these data do not prove the motor theory of speech perception, they demonstrate for the first time that word listening produces a phoneme specific activation of speech motor centres.
Action observation facilitates corticospinal excitability. This is presumably due to a premotor neural system that is active when we perform actions and when we observe actions performed by others. It has been speculated that this neural system is a precursor of neural systems subserving language. If this theory is true, we may expect hemispheric differences in the motor facilitation produced by action observation, with the language-dominant left hemisphere showing stronger facilitation than the right hemisphere. Furthermore, it has been suggested that body parts are recognized via cortical regions controlling sensory and motor processing associated with that body part. If this is true, then corticospinal facilitation during action observation should be modulated by the laterality of the observed body part. The present study addressed these two issues using TMS for each motor cortex separately as participants observed actions being performed by a left hand, a right hand, or a control stimulus on the computer screen. We found no overall difference between the right and left hemisphere for motor-evoked potential (MEP) size during action observation. However, when TMS was applied to the left motor cortex, MEPs were larger while observing right hand actions. Likewise, when TMS was applied to the right motor cortex, MEPs were larger while observing left hand actions. Our data do not suggest left hemisphere superiority in the facilitating effects of action observation on the motor system. However, they do support the notion of a sensory-motor loop according to which sensory stimulus properties (for example, the image of a left hand or a right hand) directly affect motor cortex activity, even when no motor output is required. The pattern of this effect is congruent with the pattern of motor representation in each hemisphere.
Infants between 12 and 21 days of age can imitate both facial and manual gestures; this behavior cannot be explained in terms of either conditioning or innate releasing mechanisms. Such imitation implies that human neonates can equate their own unseen behaviors with gestures they see others perform.
We recorded electrical activity from 532 neurons in the rostral part of inferior area 6 (area F5) of two macaque monkeys. Previous data had shown that neurons of this area discharge during goal-directed hand and mouth movements. We describe here the properties of a newly discovered set of F5 neurons ("mirror neurons', n = 92) all of which became active both when the monkey performed a given action and when it observed a similar action performed by the experimenter. Mirror neurons, in order to be visually triggered, required an interaction between the agent of the action and the object of it. The sight of the agent alone or of the object alone (three-dimensional objects, food) were ineffective. Hand and the mouth were by far the most effective agents. The actions most represented among those activating mirror neurons were grasping, manipulating and placing. In most mirror neurons (92%) there was a clear relation between the visual action they responded to and the motor response they coded. In approximately 30% of mirror neurons the congruence was very strict and the effective observed and executed actions corresponded both in terms of general action (e.g. grasping) and in terms of the way in which that action was executed (e.g. precision grip). We conclude by proposing that mirror neurons form a system for matching observation and execution of motor actions. We discuss the possible role of this system in action recognition and, given the proposed homology between F5 and human Brocca's region, we posit that a matching system, similar to that of mirror neurons exists in humans and could be involved in recognition of actions as well as phonetic gestures.
resonance imaging (fMRI) was used to localize brain areas that were active during the observation of actions made by another individual. Object- and non-object-relat ed actions made with different effectors (mouth, hand and foot) were presented. Observation of both object- and non-object-relat ed actions determined a somatotopically organized activation of premotor cortex. The somatotopic pattern was similar to that of the classical motor cortex homunculus. During the observation of object-related actions, an activation, also somatotopically organized,
If the contributions to this book have a common theme, it is that lip-reading is not epiphenomenal to normal speech processing; when it is missing, speech processing can go awry in a number of ways. In detailing the circumstances in which this happens, we learn more of the nature of auditory speech processes and are consequently less dismissive of the importance of lip-reading as a cognitive function.
It is a sampler of some current approaches that, by looking at lip-reading from a fresh point of view, have discovered fresh things to say about a range of cognitive processes and their development. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
This book . . . will suggest an approach to the neural basis of communication which emphasizes behavioral analysis, rather than linguistic or cognitive processes.
There are two common assumptions about the neural mechanisms of human communication which are related, and whose validity will be questioned: (1) that the critical role of the left hemisphere in communication is based on a specialization for linguistic/semantic function, and (2) that language behavior is organized quite separately from nonlanguage behaviors in the brain.
What will be proposed instead is that human communication has, during the course of evolution, become intrinsically bound to the various motor programming systems that control the relevant musculature. . . . The presumption will be that our communication systems have been shaped in part by the characteristics of certain motor systems. This view shifts the emphasis . . . to the neural mechanisms of movement selection, manual as well as vocal.
The focus of the investigation was the relationship between communicative and noncommunicative functions. In particular, we studied the ability to make a variety of oral and manual movements, and how these abilities related to speech function. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Pianists often report that pure listening to a well-trained piece of music can involuntarily trigger the respective finger movements. We designed a magnetoencephalography (MEG) experiment to compare the motor activation in pianists and nonpianists while listening to piano pieces. For pianists, we found a statistically significant increase of activity above the region of the contralateral motor cortex. Brain surface current density (BSCD) reconstructions revealed a spatial dissociation of this activity between notes preferably played by the thumb and the little finger according to the motor homunculus. Hence, we could demonstrate that pianists, when listening to well-trained piano music, exhibit involuntary motor activity involving the contralateral primary motor cortex (M1).
Can the cortical substrates for the perception of face actions be distinguished when the superficial visual qualities of these actions are very similar? Two fMRI experiments are reported. Compared with watching the face at rest, observing silent speech was associated with bilateral activation in a number of temporal cortical regions, including the superior temporal sulcus (STS). Watching face movements of similar extent and duration, but which could not be construed as speech (gurning; Experiment 1b) was not associated with activation of superior temporal cortex to the same extent, especially in the left hemisphere. Instead, the peak focus of the largest cluster of activation was in the posterior part of the inferior temporal gyrus (right, BA 37). Observing silent speech, but not gurning faces, was also associated with bilateral activation of inferior frontal cortex (BA 44 and 45). In a second study, speechreading and observing gurning faces were compared within a single experiment, using stimuli which comprised the speaker’s face and torso (and hence a much smaller image of the speaker’s face and facial actions). There was again differential engagement of superior temporal cortex which followed the pattern of Experiment 1. These findings suggest that superior temporal gyrus and neighbouring regions are activated bilaterally when subjects view face actions – at different scales – that can be interpreted as speech. This circuitry is not accessed to the same extent by visually similar, but linguistically meaningless actions. However, some temporal regions, such as the posterior part of the right superior temporal sulcus, appear to be common processing sites for processing both seen speech and gurns.
How does imitation occur? How can the motor plans necessary for imitating an action derive from the observation of that action?
Imitation may be based on a mechanism directly matching the observed action onto an internal motor representation of that
action (“direct matching hypothesis”). To test this hypothesis, normal human participants were asked to observe and imitate
a finger movement and to perform the same movement after spatial or symbolic cues. Brain activity was measured with functional
magnetic resonance imaging. If the direct matching hypothesis is correct, there should be areas that become active during
finger movement, regardless of how it is evoked, and their activation should increase when the same movement is elicited by
the observation of an identical movement made by another individual. Two areas with these properties were found in the left
inferior frontal cortex (opercular region) and the rostral-most region of the right superior parietal lobule.
The left hemisphere's dominance for movement is well known. The basis of its dominance is less clear. We have tested 16 left hemisphere (LH) patients, 17 right hemisphere (RH) patients and 12 neurologically normal controls on a battery of five tasks. The tasks were based on animal lesion and recording studies, and human imaging and magnetic stimulation studies that identified two distributed systems that are important for the selection of motor responses and object-oriented responses. The LH patients were impaired on three response selection tasks: learning to select between joystick movement responses instructed by visual cues; learning to select between analogous object-oriented responses instructed by visual cues; learning to select movements in a sequence. Although we replicated the finding that LH damage impairs sequencing, some of the impaired tasks had no sequencing element. We therefore argue that the LH deficits are best explained as an impairment of response selection. This was confirmed by showing that LH subjects were unimpaired on a more demanding task-object discrimination learning-which imposed a greater memory load but had no response selection element. Moreover, the LH deficits could not be attributed to disorganization of movement kinematics. The lesions of the impaired LH group were widespread but always included the distributed systems known to be important for response selection-the dorsolateral frontal and parietal cortices, striatum, thalamus and white matter fascicles.
Infants between 12 and 21 days of age can imitate both facial and manual gestures; this behavior cannot be explained in terms
of either conditioning or innate releasing mechanisms. Such imitation implies that human neonates can equate their own unseen
behaviors with gestures they see others perform.
MOST verbal communication occurs in contexts where the listener can see
the speaker as well as hear him. However, speech perception is normally
regarded as a purely auditory process. The study reported here
demonstrates a previously unrecognised influence of vision upon speech
perception. It stems from an observation that, on being shown a film of
a young woman's talking head, in which repeated utterances of the
syllable [ba] had been dubbed on to lip movements for [ga], normal
adults reported hearing [da]. With the reverse dubbing process, a
majority reported hearing [bagba] or [gaba]. When these subjects
listened to the soundtrack from the film, without visual input, or when
they watched untreated film, they reported the syllables accurately as
repetitions of [ba] or [ga]. Subsequent replications confirm the
reliability of these findings; they have important implications for the
understanding of speech perception.
The author in an erudite article hypothesizes the neural mechanisms of disorders of learned movement. He gives instances wherein the anterior portion of the corpus callosum, when disrupted, will result in apraxia. He further propounds the idea that Wernicke's area, the premotor and motor area, are intimately involved in this mechanism. Axial movements do not seem to be affected by pathology in the aforementioned areas and the author believes that the extrapyramidal motor system is part of the pathway utilized. It would seem that the author would have to explain Dandy's findings and conclusion: 'On several occasions when tumors of the 3rd ventricle were removed, I divided the corpus callosum in its entire anterior posterior extent without any untoward results'. (Rosner - New Rochelle, N.Y)
Asymmetries in the amplitude and velocity of oral movements were studied in 24 right-handed subjects as they produced either syllables or non-verbal movements of the mouth. Single-frame analysis of the videotaped mouth movements revealed that the right side of the mouth opened wider and faster than the left for both verbal and non-verbal movements. Moreover, the size of the right bias increased as a function of the complexity of required movements. In addition, movements embedded within a series showed a greater right bias than movements at the beginning of a series. On the whole, females exhibited larger asymmetries than males. These results provide support for the suggestion that the left hemisphere plays an important role in the control of complex motor behaviour.
A motor theory of speech perception, initially proposed to account for results of early experiments with synthetic speech, is now extensively revised to accommodate recent findings, and to relate the assumptions of the theory to those that might be made about other perceptual modes. According to the revised theory, phonetic information is perceived in a biologically distinct system, a ‘module’ specialized to detect the intended gestures of the speaker that are the basis for phonetic categories. Built into the structure of this module is the unique but lawful relationship between the gestures and the acoustic patterns in which they are variously overlapped. In consequence, the module causes perception of phonetic structure without translation from preliminary auditory impressions. Thus, it is comparable to such other modules as the one that enables an animal to localize sound. Peculiar to the phonetic module are the relation between perception and production it incorporates and the fact that it must compete with other modules for the same stimulus variations.
Patients with left hemisphere damage were found to be impaired relative to patients with right hemisphere damage, on a task in which they copied unfamiliar meaningless movements of the hand and arm. The difficulty in copying the hand movements was unrelated to the presence or absence of hemiplegia, except to the extent that a hemiplegic limb is not testable. The impairment was bilateral and equal in the two hands in cases without hemiplegia. The same patients who showed a movement copying disorder showed no difficulty in isolated finger flexion or in copying a static hand posture. Correlational data also indicated that finger flexion and the copying of movement sequences were unrelated tasks. The movement copying defect in the left hemisphere group was not significantly related to the verbal impairment; neither could it be accounted for on the basis of inadequate perception of the movements. It is suggested instead that the impairment is a disorder of motor control, unrelated to representational content. Further support for the idea that the unique functions of the left hemisphere, in speech as well, may be related to motor sequencing rather than to symbolic or language function is adduced from recent studies.
The aim of this study was to investigate the relation of apraxia to the sequential features of the motor task required and to the intra-hemispheric locus of lesion. A single movement and a multiple movement imitation test were given to 60 control patients and 60 left brain-damaged patients, among which patients with frontal and parietal lesion were identified, based on CT scan evidence. Both groups performed the tasks using the left limb. On either test left brain-damaged patients scored poorer than controls and parietal patients were significantly more impaired not only than controls, but also than frontal patients. Seventy five per cent of them performed lower than the poorest control patient. In comparison, the severity and the frequency of the motor deficit following frontal damage was much lower. In no case was there a significant difference between the discriminating power of the single movement test and of the sequence test. These findings suggest that the left parietal lobe has a leading role in motor planning and that the control it exerts over the motor cortex of the right hemisphere does not necessarily involve pathways running through the left premotor area.
A high proportion of normal subjects have speech expression controlled predominantly by the left hemisphere. Since the left hemisphere also has stronger control of the right side of the lower face, it might be expected that normal subjects would show a right-sided asymmetry in mouth opening during speech. This hypothesis was tested by measuring lip opening in 196 subjects. Of these, 150 (76%) showed greater right-side opening. This tendency was found for males, females, left- and right-handers in four experiments using two different techniques. Mouth asymmetry during speech may provide an indication of which hemisphere is dominant for expressive speech.
We recorded electrical activity from 532 neurons in the rostral part of inferior area 6 (area F5) of two macaque monkeys. Previous data had shown that neurons of this area discharge during goal-directed hand and mouth movements. We describe here the properties of a newly discovered set of F5 neurons ("mirror neurons', n = 92) all of which became active both when the monkey performed a given action and when it observed a similar action performed by the experimenter. Mirror neurons, in order to be visually triggered, required an interaction between the agent of the action and the object of it. The sight of the agent alone or of the object alone (three-dimensional objects, food) were ineffective. Hand and the mouth were by far the most effective agents. The actions most represented among those activating mirror neurons were grasping, manipulating and placing. In most mirror neurons (92%) there was a clear relation between the visual action they responded to and the motor response they coded. In approximately 30% of mirror neurons the congruence was very strict and the effective observed and executed actions corresponded both in terms of general action (e.g. grasping) and in terms of the way in which that action was executed (e.g. precision grip). We conclude by proposing that mirror neurons form a system for matching observation and execution of motor actions. We discuss the possible role of this system in action recognition and, given the proposed homology between F5 and human Brocca's region, we posit that a matching system, similar to that of mirror neurons exists in humans and could be involved in recognition of actions as well as phonetic gestures.
Infants' development of speech begins with a language-universal pattern of production that eventually becomes language specific. One mechanism contributing to this change is vocal imitation. The present study was undertaken to examine developmental change in infants' vocalizations in response to adults' vowels at 12, 16, and 20 weeks of age and test for vocal imitation. Two methodological aspects of the experiment are noteworthy: (a) three different vowel stimuli (/a/, /i/, and /u/) were videotaped and presented to infants by machine so that the adult model could not artifactually influence infant utterances, and (b) infants' vocalizations were analyzed both physically, using computerized spectrographic techniques, and perceptually by trained phoneticians who transcribed the utterances. The spectrographic analyses revealed a developmental change in the production of vowels. Infants' vowel categories become more separated in vowel space from 12 to 20 weeks of age. Moreover, vocal imitation was documented, infants listening to a particular vowel produced vocalizations resembling that vowel. A hypothesis is advanced extending Kuhl's native language magnet (NLM) model to encompass infants' speech production. It is hypothesized that infants listening to ambient language store perceptually derived representations of the speech sounds they hear which in turn serve as targets for the production of speech utterances. NLM unifies previous findings on the effects of ambient language experience on infants' speech perception and the findings reported here that short-term laboratory experience with speech is sufficient to influence infants' speech production.
In monkeys, the rostral part of ventral premotor cortex (area F5) contains neurons that discharge, both when the monkey grasps or manipulates objects and when it observes the experimenter making similar actions. These neurons (mirror neurons) appear to represent a system that matches observed events to similar, internally generated actions, and in this way forms a link between the observer and the actor. Transcranial magnetic stimulation and positron emission tomography (PET) experiments suggest that a mirror system for gesture recognition also exists in humans and includes Broca's area. We propose here that such an observation/execution matching system provides a necessary bridge from'doing' to'communicating',as the link between actor and observer becomes a link between the sender and the receiver of each message.
This article is subdivided into two parts. In the first part we review the properties of a particular class of premotor neurons, the "mirror" neurons. With this term we define neurons that discharge both when the monkey makes a particular action and when it observes another individual (monkey or human) making a similar action. The second part is an attempt to give a neurophysiological account of the mechanisms underlying behaviors where an individual reproduces, overtly or internally, movements or actions made by another individual. We will refer to these behaviors as "resonance behaviors". We distinguish two types of resonance behavior. The first type is characterized by imitation, immediate or with delay, of movements made by other individuals. Examples of resonance behavior of this type are the "imitative" behaviors observed in birds, young infants and patients with frontal lesions. The second type of resonance behavior is characterized by the occurrence, at the observation of an action, of a neural pattern, which, when internally generated, determines the making of the observed action. In this type of resonance behavior the observed action is, typically, not repeated (overtly). We argue that resonance behavior of the second type is at the basis of the understanding of actions made by others. At the end of the article we review evidence of mirror mechanisms in humans and discuss their anatomical localizations.
The evolution of speech can be studied independently of the evolution of language, with the advantage that most aspects of speech acoustics, physiology and neural control are shared with animals, and thus open to empirical investigation. At least two changes were necessary prerequisites for modern human speech abilities: (1) modification of vocal tract morphology, and (2) development of vocal imitative ability. Despite an extensive literature, attempts to pinpoint the timing of these changes using fossil data have proven inconclusive. However, recent comparative data from nonhuman primates have shed light on the ancestral use of formants (a crucial cue in human speech) to identify individuals and gauge body size. Second, comparative analysis of the diverse vertebrates that have evolved vocal imitation (humans, cetaceans, seals and birds) provides several distinct, testable hypotheses about the adaptive function of vocal mimicry. These developments suggest that, for understanding the evolution of speech, comparative analysis of living species provides a viable alternative to fossil data. However, the neural basis for vocal mimicry and for mimesis in general remains unknown.
Paired-pulse transcranial magnetic stimulation (TMS) was used to examine changes in cortical excitability during action observation. We stimulated the left primary motor cortex (M1) of eight healthy volunteers during rest, observation of handwriting and observation of arm movements. Motor evoked potentials (MEP) were recorded from the first dorsal intereosseous (FDI) and biceps (BIC) muscles. Our results showed that action observation induced a facilitation of the MEP amplitude evoked by the single test stimulus and reduced intracortical inhibition and facilitation at 3 ms and 12 ms interstimulus intervals (ISIs), respectively, during paired-pulse stimulation. These changes were specific for the muscle involved in the observed action. Our study presents further evidence that motor excitability is significantly modified when the subject observes an action performed by another individual.
There is growing evidence that observation of actions performed by other individuals activates observer's cortical motor areas. This matching of observed actions on the observer's motor repertoire could be at the basis of action recognition. Here we investigated if action observation, in addition to cortical motor areas, involves also low level motor structures mimicking the observed actions as if they were performed by the observer. Spinal cord excitability was tested by eliciting the H-reflex in a finger flexor muscle (flexor digitorum superficialis) in humans looking at goal-directed hand actions presented on a TV screen. We found that, in the absence of any detectable muscle activity, there was in the observers a significant modulation of the monosynaptic reflex size, specifically related to the different phases of the observed movement. The recorded H-reflex rapidly increased in size during hand opening, it was depressed during hand closing and quickly recovered during object lifting. This modulation pattern is, however, opposite to that occurring when the recorded muscles are actually executing the observed action [Lemon et al. (1995) J. Neurosci., 15, 6145-56]. Considering that, when investigated at cortical level the modulation pattern of corticospinal excitability replicates the observed movements [Fadiga et al. (1995) J. Neurophysiol., 73, 2608-2611], this spinal 'inverted mirror' behaviour might be finalised to prevent the overt replica of the seen action.
Functional magnetic resonance imaging (fMRI) was used to localize brain areas that were active during the observation of actions made by another individual. Object- and non-object-related actions made with different effectors (mouth, hand and foot) were presented. Observation of both object- and non-object-related actions determined a somatotopically organized activation of premotor cortex. The somatotopic pattern was similar to that of the classical motor cortex homunculus. During the observation of object-related actions, an activation, also somatotopically organized, was additionally found in the posterior parietal lobe. Thus, when individuals observe an action, an internal replica of that action is automatically generated in their premotor cortex. In the case of object-related actions, a further object-related analysis is performed in the parietal lobe, as if the subjects were indeed using those objects. These results bring the previous concept of an action observation/execution matching system (mirror system) into a broader perspective: this system is not restricted to the ventral premotor cortex, but involves several somatotopically organized motor circuits.
The effects of different phases of an observed movement on the modulation of cortical motor output were studied by means of transcranial magnetic stimulation (TMS). A video-clip of a reaching-grasping action was shown and single TMS pulses were delivered during its passive observation. Times of cortical stimulation were related to the phases of the shown movement, locking them to the appearance of specific kinematic landmarks. The amplitude of the motor evoked potentials (MEPs) induced by TMS in the first dorsal interosseus (FDI) muscle was modulated by the amount of the observed finger aperture. The presence of such an effect is consistent with the notion of a mirror neuron system in premotor areas that couples action execution and action observation also in terms of temporal coding.
Observation of limb movements in human subjects resulted in increased motor-evoked potential (MEP) amplitude elicited by magnetic stimulation of motor cortex in the muscles involved in that movement, suggesting that an observation-execution matching (OEM) system exists in humans. We investigated whether the OEM system is activated by speech gestures presented in the visual and auditory modalities. We found that visual observation of speech movement enhanced MEP amplitude specifically in muscles involved in production of the observed speech. In contrast, listening to the sound did not produce MEP enhancement. The findings suggest that the OEM system may be modality specific. It may be involved in action recognition in the visual modality, but is not responsible for perception of simple items of sound.
What are the neural bases of action understanding? Although this capacity could merely involve visual analysis of the action, it has been argued that we actually map this visual information onto its motor representation in our nervous system. Here we discuss evidence for the existence of a system, the 'mirror system', that seems to serve this mapping function in primates and humans, and explore its implications for the understanding and imitation of action.
Can the cortical substrates for the perception of face actions be distinguished when the superficial visual qualities of these actions are very similar? Two fMRI experiments are reported. Compared with watching the face at rest, observing silent speech was associated with bilateral activation in a number of temporal cortical regions, including the superior temporal sulcus (STS). Watching face movements of similar extent and duration, but which could not be construed as speech (gurning; Experiment 1b) was not associated with activation of superior temporal cortex to the same extent, especially in the left hemisphere. Instead, the peak focus of the largest cluster of activation was in the posterior part of the inferior temporal gyrus (right, BA 37). Observing silent speech, but not gurning faces, was also associated with bilateral activation of inferior frontal cortex (BA 44 and 45). In a second study, speechreading and observing gurning faces were compared within a single experiment, using stimuli which comprised the speaker's face and torso (and hence a much smaller image of the speaker's face and facial actions). There was again differential engagement of superior temporal cortex which followed the pattern of Experiment 1. These findings suggest that superior temporal gyrus and neighbouring regions are activated bilaterally when subjects view face actions--at different scales--that can be interpreted as speech. This circuitry is not accessed to the same extent by visually similar, but linguistically meaningless actions. However, some temporal regions, such as the posterior part of the right superior temporal sulcus, appear to be common processing sites for processing both seen speech and gurns.
Observation–execution matchingsystemfor speech
- M Sundara
- Ak Namasivayam
- Chen
Sundara M, Namasivayam AK, Chen R. Observation–execution matchingsystemfor speech: NeuroReport 2001;12:1341–4.
The anatomy coloring book
- W Kapit
- L M Elson
Kapit W, Elson LM. The anatomy coloring book. New York: Harper & Row, 1977.
The apraxias: neural mechanisms of disorders of learned movement
- Geshwind
Oral asymmetries during verbal and non-verbal movements of the mouth
- Wylie