Motor System In Speech Perception Research Articles

Neural dynamics of the motor system during language development

Motor and sensory cortices are traditionally thought to be functionally separate systems. However, many studies have shown their roles in both action and perception to be highly integrated. In particular, this has been observed in regard to speech, where listening to speech sounds elicits neural activity in motor regions of the brain. Two datasets containing magnetoencephalography (MEG) data from 2-, 6-, 7-, and 11-month-old infants were used to investigate the role of the motor system in speech perception throughout various stages of language development. We examined the relationship between activation in auditory sensory and motor regions of the brain with respect to: (1) the development of neural responses with increasing age, and (2) potential differences between speech and nonspeech auditory signals. Results showed that motor regions are activated during speech perception across all ages. At 2 months of age, infants show activity in both motor and motor planning regions in response to speech, but not nonspeech, acoustic stimuli. Our data suggest that infants’ activation of sensory and motor brain regions in response to speech does not require experience producing speech.

Effect of Bilateral Opercular Syndrome on Speech Perception.

Speech perception ability and structural neuroimaging were investigated in two cases of bilateral opercular syndrome. Due to bilateral ablation of the motor control center for the lower face and surrounds, these rare cases provide an opportunity to evaluate the necessity of cortical motor representations for speech perception, a cornerstone of some neurocomputational theories of language processing. Speech perception, including audiovisual integration (i.e., the McGurk effect), was mostly unaffected in these cases, although verbal short-term memory impairment hindered performance on several tasks that are traditionally used to evaluate speech perception. The results suggest that the role of the cortical motor system in speech perception is context-dependent and supplementary, not inherent or necessary.

Motor engagement relates to accurate perception of phonemes and audiovisual words, but not auditory words

A longstanding debate has surrounded the role of the motor system in speech perception, but progress in this area has been limited by tasks that only examine isolated syllables and conflate decision-making with perception. Using an adaptive task that temporally isolates perception from decision-making, we examined an EEG signature of motor activity (sensorimotor μ/beta suppression) during the perception of auditory phonemes, auditory words, audiovisual words, and environmental sounds while holding difficulty constant at two levels (Easy/Hard). Results revealed left-lateralized sensorimotor μ/beta suppression that was related to perception of speech but not environmental sounds. Audiovisual word and phoneme stimuli showed enhanced left sensorimotor μ/beta suppression for correct relative to incorrect trials, while auditory word stimuli showed enhanced suppression for incorrect trials. Our results demonstrate that motor involvement in perception is left-lateralized, is specific to speech stimuli, and it not simply the result of domain-general processes. These results provide evidence for an interactive network for speech perception in which dorsal stream motor areas are dynamically engaged during the perception of speech depending on the characteristics of the speech signal. Crucially, this motor engagement has different effects on the perceptual outcome depending on the lexicality and modality of the speech stimulus.

Speech Perception Triggers Articulatory Action: Evidence From Mechanical Stimulation

Neuroimaging studies show that the brain articulatory motor system is activated during speech perception. These results, however, cannot determine whether the motor system is engaged in motor simulation (e.g., lip movement) or in non-motor computations. To gauge the causal role of the articulatory motor system, here we examine the effect of mechanical stimulation. Participants heard speech tokens, ambiguous with respect to voicing—either labial (ba/pa) or coronal (da/ta)—while lightly biting on either the lips or tongue. Compared to incongruent stimulation (e.g., lips, with da/ta), congruent stimulation (e.g., tongue, with da/ta) shifted the voicing percepts and improved discrimination sensitivity (d’). Results are the first to demonstrate that adults engage the articulatory motor system in speech perception even when it is irrelevant to response. The convergence with transcranial magnetic stimulation experiments demonstrates that speech perception engages articulatory action. These conclusions illuminate the links between embodiment and cognition.

The role of frontal speech motor system in speech perception: An fMRI study

The role of frontal speech motor system in speech perception: An fMRI study

Reanalyzing neurocognitive data on the role of the motor system in speech perception within COSMO, a Bayesian perceptuo-motor model of speech communication

While neurocognitive data provide clear evidence for the involvement of the motor system in speech perception, its precise role and the way motor information is involved in perceptual decision remain unclear. In this paper, we discuss some recent experimental results in light of COSMO, a Bayesian perceptuo-motor model of speech communication. COSMO enables us to model both speech perception and speech production with probability distributions relating phonological units with sensory and motor variables. Speech perception is conceived as a sensory-motor architecture combining an auditory and a motor decoder thanks to a Bayesian fusion process. We propose the sketch of a neuroanatomical architecture for COSMO, and we capitalize on properties of the auditory vs. motor decoders to address three neurocognitive studies of the literature. Altogether, this computational study reinforces functional arguments supporting the role of a motor decoding branch in the speech perception process.

A causal test of the motor theory of speech perception: a case of impaired speech production and spared speech perception

The debate about the causal role of the motor system in speech perception has been reignited by demonstrations that motor processes are engaged during the processing of speech sounds. Here, we evaluate which aspects of auditory speech processing are affected, and which are not, in a stroke patient with dysfunction of the speech motor system. We found that the patient showed a normal phonemic categorical boundary when discriminating two non-words that differ by a minimal pair (e.g., ADA–AGA). However, using the same stimuli, the patient was unable to identify or label the non-word stimuli (using a button-press response). A control task showed that he could identify speech sounds by speaker gender, ruling out a general labelling impairment. These data suggest that while the motor system is not causally involved in perception of the speech signal, it may be used when other cues (e.g., meaning, context) are not available.

The shadow of a doubt? Evidence for perceptuo-motor linkage during auditory and audiovisual close-shadowing.

One classical argument in favor of a functional role of the motor system in speech perception comes from the close-shadowing task in which a subject has to identify and to repeat as quickly as possible an auditory speech stimulus. The fact that close-shadowing can occur very rapidly and much faster than manual identification of the speech target is taken to suggest that perceptually induced speech representations are already shaped in a motor-compatible format. Another argument is provided by audiovisual interactions often interpreted as referring to a multisensory-motor framework. In this study, we attempted to combine these two paradigms by testing whether the visual modality could speed motor response in a close-shadowing task. To this aim, both oral and manual responses were evaluated during the perception of auditory and audiovisual speech stimuli, clear or embedded in white noise. Overall, oral responses were faster than manual ones, but it also appeared that they were less accurate in noise, which suggests that motor representations evoked by the speech input could be rough at a first processing stage. In the presence of acoustic noise, the audiovisual modality led to both faster and more accurate responses than the auditory modality. No interaction was however, observed between modality and response. Altogether, these results are interpreted within a two-stage sensory-motor framework, in which the auditory and visual streams are integrated together and with internally generated motor representations before a final decision may be available.

Effects of visuoauditive integration on motor system in speech perception: A TMS study

Unilateral spatial neglect frequently occurs after right-hemisphere stroke. It represents a major problem in the domain of public health, since it prevents patients from orienting or responding to left-sided stimuli. The exact anatomical location of lesions underlying the manifestation of this syndrome is currently debated (Bartolomeo, 2012). In the present study, we used a longitudinal approach in order to identify the lesional predictors of chronic neglect in longrange white matter bundles. We present a longitudinal study of 37 patients with right-hemisphere damage, tested at the acute/subacute phase and at more than 1 year after the stroke. 27 patients presented signs of spatial neglect in the acute/subacute phase. Each patient underwent a radiological assessment including a DTI sequence, (50 directions; bvalue of 1000 mm2/s). Voxelwise statistical analysis of the fractional anisotropy (FA) data was carried out using TBSS (Tract-Based Spatial Statistics, Smith, 2006). The longitudinal follow-up revealed that only 10 patients (27%) recovered from neglect at retest. In acute/subacute neglect, a lower FAwas found in the way of the right Superior Longitudinal fasciculus (SLF II and III) and of the corpus callosum. In the chronic phase, TBSS analysis showed the implication of the posterior portion of the corpus callosum (splenium) and of SLF II & III. The voxelwise correlation between a cancellation task (Bells test) and FA maps found a lower FA in the way of the anterior corpus callosum, local frontal and fronto-parietal white matter (SLF II and III), and in the thalamus. Our results confirm a key role of fronto-parietal disconnection in the emergence and chronic persistence of neglect (Thiebaut de Schotten et al., 2012). Moreover, we demonstrated an implication of interhemispheric disconnection (splenium and forceps major) in chronic neglect. These findings support the hypothesis that interhemispheric disconnection may deprive the right frontoparietal pathway of visual inputs, amputing the brain reconstruction of the left hemi-space (Tomaiuolo et al., 2010), and that chronic neglect at least in part results from the activity of an isolated left hemisphere (Bartolomeo et al., 2007).

Using TMS to study the role of the articulatory motor system in speech perception

Background: The ability to communicate using speech is a remarkable skill, which requires precise coordination of articulatory movements and decoding of complex acoustic signals. According to the traditional view, speech production and perception rely on motor and auditory brain areas, respectively. However, there is growing evidence that auditory-motor circuits support both speech production and perception. Aims: In this article we provide a review of how transcranial magnetic stimulation (TMS) has been used to investigate the excitability of the motor system during listening to speech and the contribution of the motor system to performance in various speech perception tasks. We also discuss how TMS can be used in combination with brain-imaging techniques to study interactions between motor and auditory systems during speech perception. Main contribution: TMS has proven to be a powerful tool to investigate the role of the articulatory motor system in speech perception. Conclusions: TMS studies have provided support for the view that the motor structures that control the movements of the articulators contribute not only to speech production but also to speech perception.

Teaching and Learning Guide for: Mirror Neurons, the Motor System, and Language – From the Motor Theory to Embodied Cognition and Beyond

Teaching and Learning Guide for: Mirror Neurons, the Motor System, and Language – From the Motor Theory to Embodied Cognition and Beyond

The Perception-for-Action-Control Theory (PACT): A perceptuo-motor theory of speech perception

It is an old-standing debate in the field of speech communication to determine whether speech perception involves auditory or multisensory representations and processing, independently on any procedural knowledge about the production of speech units or on the contrary if it is based on a recoding of the sensory input in terms of articulatory gestures, as posited in the Motor Theory of Speech Perception. The discovery of mirror neurons in the last 15 years has strongly renewed the interest for motor theories. However, while these neurophysiological data clearly reinforce the plausibility of the role of motor properties in perception, it could lead in our view to incorrectly de-emphasise the role of perceptual shaping, crucial in speech communication. The so-called Perception-for-Action-Control Theory (PACT) aims at defining a theoretical framework connecting in a principled way perceptual shaping and motor procedural knowledge in speech multisensory processing in the human brain. In this paper, the theory is presented in details. It is described how this theory fits with behavioural and linguistic data, concerning firstly vowel systems in human languages, and secondly the perceptual organization of the speech scene. Finally a neuro-computational framework is presented in connection with recent data on the possible functional role of the motor system in speech perception.

A mediating role of the premotor cortex in phoneme segmentation

Consistent with a functional role of the motor system in speech perception, disturbing the activity of the left ventral premotor cortex by means of repetitive transcranial magnetic stimulation (rTMS) has been shown to impair auditory identification of syllables that were masked with white noise. However, whether this region is crucial for speech perception under normal listening conditions remains debated. To directly test this hypothesis, we applied rTMS to the left ventral premotor cortex and participants performed auditory speech tasks involving the same set of syllables but differing in the use of phonemic segmentation processes. Compared to sham stimulation, rTMS applied over the ventral premotor cortex resulted in slower phoneme discrimination requiring phonemic segmentation. No effect was observed in phoneme identification and syllable discrimination tasks that could be performed without need for phonemic segmentation. The findings demonstrate a mediating role of the ventral premotor cortex in speech segmentation under normal listening conditions and are interpreted in relation to theories assuming a link between perception and action in the human speech processing system.