Role In Speech Perception Research Articles

Sonority's Effect as a Surface Cue on Lexical Speech Perception of Children With Cochlear Implants.

Sonority is the relative perceptual prominence/loudness of speech sounds of the same length, stress, and pitch. Children with cochlear implants (CIs), with restored audibility and relatively intact temporal processing, are expected to benefit from the perceptual prominence cues of highly sonorous sounds. Sonority also influences lexical access through the sonority-sequencing principle (SSP), a grammatical phonotactic rule, which facilitates the recognition and segmentation of syllables within speech. The more nonsonorous the onset of a syllable is, the larger is the degree of sonority rise to the nucleus, and the more optimal the SSP. Children with CIs may experience hindered or delayed development of the language-learning rule SSP, as a result of their deprived/degraded auditory experience. The purpose of the study was to explore sonority's role in speech perception and lexical access of prelingually deafened children with CIs. A case-control study with 15 children with CIs, 25 normal-hearing children (NHC), and 50 normal-hearing adults was conducted, using a lexical identification task of novel, nonreal CV-CV words taught via fast mapping. The CV-CV words were constructed according to four sonority conditions, entailing syllables with sonorous onsets/less optimal SSP (SS) and nonsonorous onsets/optimal SSP (NS) in all combinations, that is, SS-SS, SS-NS, NS-SS, and NS-NS. Outcome measures were accuracy and reaction times (RTs). A subgroup analysis of 12 children with CIs pair matched to 12 NHC on hearing age aimed to study the effect of oral-language exposure period on the sonority-related performance. The children groups showed similar accuracy performance, overall and across all the sonority conditions. However, within-group comparisons showed that the children with CIs scored more accurately on the SS-SS condition relative to the NS-NS and NS-SS conditions, while the NHC performed equally well across all conditions. Additionally, adult-comparable accuracy performance was achieved by the children with CIs only on the SS-SS condition, as opposed to NS-SS, SS-NS, and SS-SS conditions for NHC. Accuracy analysis of the subgroups of children matched in hearing age showed similar results. Overall longer RTs were recorded by the children with CIs on the sonority-treated lexical task, specifically on the SS-SS condition compared with age-matched controls. However, the subgroup analysis showed that both groups of children did not differ on RTs. Children with CIs performed better in lexical tasks relying on the sonority perceptual prominence cues, as in SS-SS condition, than on SSP initial relying conditions as NS-NS and NS-SS. Template-driven word learning, an early word-learning strategy, appears to play a role in the lexical access of children with CIs whether matched in hearing age or not. The SS-SS condition acts as a preferred word template. The longer RTs brought about by the highly accurate SS-SS condition in children with CIs is possibly because listening becomes more effortful. The lack of RTs difference between the children groups when matched on hearing age points out the importance of oral-language exposure period as a key factor in developing the auditory processing skills.

The Role of Speech Perception in French Nasal Vowel Adaptation: Phonemic vs. Acoustic Processing

The Role of Speech Perception in French Nasal Vowel Adaptation: Phonemic vs. Acoustic Processing

Olivocochlear Efferent Activity Is Associated With the Slope of the Psychometric Function of Speech Recognition in Noise.

The medial olivocochlear (MOC) efferent system can modify cochlear function to improve sound detection in noise, but its role in speech perception in noise is unclear. The purpose of this study was to determine the association between MOC efferent activity and performance on two speech-in-noise tasks at two signal-to-noise ratios (SNRs). It was hypothesized that efferent activity would be more strongly correlated with performance at the more challenging SNR, relative to performance at the less challenging SNR. Sixteen adults aged 35 to 73 years participated. Subjects had pure-tone averages ≤25 dB HL and normal middle ear function. High-frequency pure-tone averages were computed across 3000 to 8000 Hz and ranged from 6.3 to 48.8 dB HL. Efferent activity was assessed using contralateral suppression of transient-evoked otoacoustic emissions (TEOAEs) measured in right ears, and MOC activation was achieved by presenting broadband noise to left ears. Contralateral suppression was expressed as the decibel change in TEOAE magnitude obtained with versus without the presence of the broadband noise. TEOAE responses were also examined for middle ear muscle reflex activation and synchronous spontaneous otoacoustic emissions (SSOAEs). Speech-in-noise perception was assessed using the closed-set coordinate response measure word recognition task and the open-set Institute of Electrical and Electronics Engineers sentence task. Speech and noise were presented to right ears at two SNRs. Performance on each task was scored as percent correct. Associations between contralateral suppression and speech-in-noise performance were quantified using partial rank correlational analyses, controlling for the variables age and high-frequency pure-tone average. One subject was excluded due to probable middle ear muscle reflex activation. Subjects showed a wide range of contralateral suppression values, consistent with previous reports. Three subjects with SSOAEs had similar contralateral suppression results as subjects without SSOAEs. The magnitude of contralateral suppression was not significantly correlated with speech-in-noise performance on either task at a single SNR (p > 0.05), contrary to hypothesis. However, contralateral suppression was significantly correlated with the slope of the psychometric function, computed as the difference between performance levels at the two SNRs divided by 3 (decibel difference between the 2 SNRs) for the coordinate response measure task (partial rs = 0.59; p = 0.04) and for the Institute of Electrical and Electronics Engineers task (partial rs = 0.60; p = 0.03). In a group of primarily older adults with normal hearing or mild hearing loss, olivocochlear efferent activity assessed using contralateral suppression of TEOAEs was not associated with speech-in-noise performance at a single SNR. However, auditory efferent activity appears to be associated with the slope of the psychometric function for both a word and sentence recognition task in noise. Results suggest that individuals with stronger MOC efferent activity tend to be more responsive to changes in SNR, where small increases in SNR result in better speech-in-noise performance relative to individuals with weaker MOC efferent activity. Additionally, the results suggest that the slope of the psychometric function may be a more useful metric than performance at a single SNR when examining the relationship between speech recognition in noise and MOC efferent activity.

Speech understanding in noise in elderly adults: the effect of inhibitory control and syntactic complexity.

Previous research has suggested that speech perception in elderly adults is influenced not only by age-related hearing loss or presbycusis but also by declines in cognitive abilities, by background noise and by the syntactic complexity of the message. To gain further insight into the influence of these cognitive as well as acoustic and linguistic factors on speech perception in elderly adults by investigating inhibitory control as a listener characteristic and background noise type and syntactic complexity as input characteristics. Phoneme identification was measured in different noise conditions and in different linguistic contexts (single words, sentences with varying syntactic complexity). Additionally, inhibitory control was measured using a visual stimulus-response matching task. Fifty-one adults participated in this study, including elderly adults with age-related hearing loss (n = 9) and with normal hearing (n = 17), and a control group of normal hearing younger adults (n = 25). The analysis revealed that elderly adults with normal hearing and with hearing loss were less likely to identify successfully phonemes in single words than younger normal hearing controls. In the context of sentences, only elderly adults with hearing loss had a lower odds of correct phoneme perception than the control group. Additionally, in elderly adults with hearing loss, phoneme-in-sentence perception was linked to age-related declines in inhibitory control. In all participants, phoneme identification in sentences was influenced by both noise type and syntactic complexity. Inhibitory control and syntactic complexity might play a significant role in speech perception, especially in elderly listeners. These factors might also influence the results of clinical assessments of speech perception. Testing procedures thus need to be selected and their results interpreted carefully with these influences in mind.

The role of temporal fine structure in tone recognition and music perception

The sound signal can be decomposed into temporal envelope and temporal fine structure information. The temporal envelope information is crucial for speech perception in quiet environment, and the temporal fine structure information plays an important role in speech perception in noise, Mandarin tone recognition and music perception, especially the pitch and melody perception.

The effect of prior knowledge and intelligibility on the cortical entrainment response to speech.

It has been suggested that cortical entrainment plays an important role in speech perception by helping to parse the acoustic stimulus into discrete linguistic units. However, the question of whether the entrainment response to speech depends on the intelligibility of the stimulus remains open. Studies addressing this question of intelligibility have, for the most part, significantly distorted the acoustic properties of the stimulus to degrade the intelligibility of the speech stimulus, making it difficult to compare across "intelligible" and "unintelligible" conditions. To avoid these acoustic confounds, we used priming to manipulate the intelligibility of vocoded speech. We used EEG to measure the entrainment response to vocoded target sentences that are preceded by natural speech (nonvocoded) prime sentences that are either valid (match the target) or invalid (do not match the target). For unintelligible speech, valid primes have the effect of restoring intelligibility. We compared the effect of priming on the entrainment response for both 3-channel (unintelligible) and 16-channel (intelligible) speech. We observed a main effect of priming, suggesting that the entrainment response depends on prior knowledge, but not a main effect of vocoding (16 channels vs. 3 channels). Furthermore, we found no difference in the effect of priming on the entrainment response to 3-channel and 16-channel vocoded speech, suggesting that for vocoded speech, entrainment response does not depend on intelligibility.NEW & NOTEWORTHY Neural oscillations have been implicated in the parsing of speech into discrete, hierarchically organized units. Our data suggest that these oscillations track the acoustic envelope rather than more abstract linguistic properties of the speech stimulus. Our data also suggest that prior experience with the stimulus allows these oscillations to better track the stimulus envelope.

Superoptimal Perceptual Integration Suggests a Place-Based Representation of Pitch at High Frequencies.

Pitch, the perceptual correlate of sound repetition rate or frequency, plays an important role in speech perception, music perception, and listening in complex acoustic environments. Despite the perceptual importance of pitch, the neural mechanisms that underlie it remain poorly understood. Although cortical regions responsive to pitch have been identified, little is known about how pitch information is extracted from the inner ear itself. The two primary theories of peripheral pitch coding involve stimulus-driven spike timing, or phase locking, in the auditory nerve (time code), and the spatial distribution of responses along the length of the cochlear partition (place code). To rule out the use of timing information, we tested pitch discrimination of very high-frequency tones (>8 kHz), well beyond the putative limit of phase locking. We found that high-frequency pure-tone discrimination was poor, but when the tones were combined into a harmonic complex, a dramatic improvement in discrimination ability was observed that exceeded performance predicted by the optimal integration of peripheral information from each of the component frequencies. The results are consistent with the existence of pitch-sensitive neurons that rely only on place-based information from multiple harmonically related components. The results also provide evidence against the common assumption that poor high-frequency pure-tone pitch perception is the result of peripheral neural-coding constraints. The finding that place-based spectral coding is sufficient to elicit complex pitch at high frequencies has important implications for the design of future neural prostheses to restore hearing to deaf individuals.SIGNIFICANCE STATEMENT The question of how pitch is represented in the ear has been debated for over a century. Two competing theories involve timing information from neural spikes in the auditory nerve (time code) and the spatial distribution of neural activity along the length of the cochlear partition (place code). By using very high-frequency tones unlikely to be coded via time information, we discovered that information from the individual harmonics is combined so efficiently that performance exceeds theoretical predictions based on the optimal integration of information from each harmonic. The findings have important implications for the design of auditory prostheses because they suggest that enhanced spatial resolution alone may be sufficient to restore pitch via such implants.

Cross-linguistic perception of continuous speech: Neural entrainment to the speech amplitude envelope

Brain oscillations in the auditory cortex become entrained to slow amplitude fluctuations in the speech signal (i.e., amplitude envelope) during speech comprehension. Previous research has suggested that this cortical activity plays an important role in speech perception by aligning neuronal excitability to parts of the incoming speech signal that contain linguistic information such as syllables. However, it remains unclear how cortical entrainment to the speech envelope relates to higher-level linguistic processes during speech comprehension. The aim of the present study was to see if cortical entrainment to the amplitude envelope varies depending on whether or not the listener understands the linguistic content of the speech signal. To this end, the phase-locking between neural oscillations and amplitude envelopes of speech were measured in EEG recordings from listeners with different linguistic backgrounds (i.e., native English and Korean speakers) while they heard continuous speech in three languages ...

Enhancing speech envelope by integrating hair-cell adaptation into cochlear implant processing

Cochlear implants (CIs) bypass some of the mechanisms that underlie normal neural behavior as occurs in acoustic hearing. One such neural mechanism is short-term adaptation, which has been proposed to have a significant role in speech perception. Acoustically-evoked neural adaptation has been mainly attributed to the depletion of neurotransmitter in the hair-cell to auditory-nerve synapse and is therefore not fully present in CI stimulation. This study evaluated a signal processing method that integrated a physiological model of hair-cell adaptation into CI speech processing. The linear high-pass adaptation process expanded the range of rapid variations of the electrical signal generated by the clinical processing strategy. Speech perception performance with the adaptation-based processing was compared to that of the clinical strategy in seven CI users. While there was large variability across subjects, the new processing improved sentence recognition and consonant identification scores in quiet in all the tested subjects with an average improvement of 8% and 6% respectively. Consonant recognition scores in babble noise were improved at the higher signal-to-noise ratios tested (10 and 6 dB) only. Information transfer analysis of consonant features showed significant improvements for manner and place of articulation features, but not for voicing. Enhancement of within-channel envelope cues was confirmed by consonant recognition results obtained with single-channel strategies that presented the overall amplitude envelope of the signal on a single active electrode. Adaptation-inspired envelope enhancement techniques can potentially improve perception of important speech features by CI users.

Aging Affects Neural Synchronization to Speech-Related Acoustic Modulations

As people age, speech perception problems become highly prevalent, especially in noisy situations. In addition to peripheral hearing and cognition, temporal processing plays a key role in speech perception. Temporal processing of speech features is mediated by synchronized activity of neural oscillations in the central auditory system. Previous studies indicate that both the degree and hemispheric lateralization of synchronized neural activity relate to speech perception performance. Based on these results, we hypothesize that impaired speech perception in older persons may, in part, originate from deviances in neural synchronization. In this study, auditory steady-state responses that reflect synchronized activity of theta, beta, low and high gamma oscillations (i.e., 4, 20, 40, and 80 Hz ASSR, respectively) were recorded in young, middle-aged, and older persons. As all participants had normal audiometric thresholds and were screened for (mild) cognitive impairment, differences in synchronized neural activity across the three age groups were likely to be attributed to age. Our data yield novel findings regarding theta and high gamma oscillations in the aging auditory system. At an older age, synchronized activity of theta oscillations is increased, whereas high gamma synchronization is decreased. In contrast to young persons who exhibit a right hemispheric dominance for processing of high gamma range modulations, older adults show a symmetrical processing pattern. These age-related changes in neural synchronization may very well underlie the speech perception problems in aging persons.

Decoding Articulatory Features from fMRI Responses in Dorsal Speech Regions

The brain's circuitry for perceiving and producing speech may show a notable level of overlap that is crucial for normal development and behavior. The extent to which sensorimotor integration plays a role in speech perception remains highly controversial, however. Methodological constraints related to experimental designs and analysis methods have so far prevented the disentanglement of neural responses to acoustic versus articulatory speech features. Using a passive listening paradigm and multivariate decoding of single-trial fMRI responses to spoken syllables, we investigated brain-based generalization of articulatory features (place and manner of articulation, and voicing) beyond their acoustic (surface) form in adult human listeners. For example, we trained a classifier to discriminate place of articulation within stop syllables (e.g., /pa/ vs /ta/) and tested whether this training generalizes to fricatives (e.g., /fa/ vs /sa/). This novel approach revealed generalization of place and manner of articulation at multiple cortical levels within the dorsal auditory pathway, including auditory, sensorimotor, motor, and somatosensory regions, suggesting the representation of sensorimotor information. Additionally, generalization of voicing included the right anterior superior temporal sulcus associated with the perception of human voices as well as somatosensory regions bilaterally. Our findings highlight the close connection between brain systems for speech perception and production, and in particular, indicate the availability of articulatory codes during passive speech perception. Sensorimotor integration is central to verbal communication and provides a link between auditory signals of speech perception and motor programs of speech production. It remains highly controversial, however, to what extent the brain's speech perception system actively uses articulatory (motor), in addition to acoustic/phonetic, representations. In this study, we examine the role of articulatory representations during passive listening using carefully controlled stimuli (spoken syllables) in combination with multivariate fMRI decoding. Our approach enabled us to disentangle brain responses to acoustic and articulatory speech properties. In particular, it revealed articulatory-specific brain responses of speech at multiple cortical levels, including auditory, sensorimotor, and motor regions, suggesting the representation of sensorimotor information during passive speech perception.

The Role of Speech Perception in Persistent Speech Sound Disorder

Children with persistent speech sound disorder (SSD) continue to exhibit speech production errors well beyond the age at which they are expected to have resolved, often even after attempts at remed...

The Effect of Intensified Language Exposure on Accommodating Talker Variability.

This study systematically examined the role of intensified exposure to a second language on accommodating talker variability. English native listeners (n = 37) were compared with Mandarin listeners who had either lived in the United States for an extended period of time (n = 33) or had lived only in China (n = 44). Listeners responded to target words in an English word-monitoring task in which sequences of words were randomized. Half of the sequences were spoken by a single talker and the other half by multiple talkers. Mandarin listeners living in China were slower and less accurate than both English listeners and Mandarin listeners living in the United States. Mandarin listeners living in the United States were less accurate than English natives only in the more cognitively demanding mixed-talker condition. Mixed-talker speech affects processing in native and nonnative listeners alike, although the decrement is larger in nonnatives and further exaggerated in less proficient listeners. Language immersion improves listeners' ability to resolve talker variability, and this suggests that immersion may automatize nonnative processing, freeing cognitive resources that may play a crucial role in speech perception. These results lend support to the active control model of speech perception.

Auditory envelope following responses in the mature and developing human brain

Event Abstract Back to Event Auditory envelope following responses in the mature and developing human brain Huizhen Tang1*, Jon Brock1, Stephen Crain2 and Blake Johnson1 1 Macquarie University , Cognitive Science , Australia 2 Macquarie University , Linguistics , Australia Recent theories of speech perception propose that the speech envelope (the overall waveform of the speech signal) plays a crucial role in speech perception by aligning brain excitability patterns with the intensity fluctuations of the speech sounds. We tested two main hypotheses derived from these theories: (1) That the sound envelope provides crucial cues for encoding of temporal information in sounds; (2) that temporal encoding is not fully mature in preschool-aged children (3 to 5 years old). The acoustic stimulus was a broadband noise amplitude-modulated in a continuous sweep of frequencies from 1 to 80 Hz. Brain responses were measured with magnetoencephalography. The adult temporal modulation transfer function showed precise and continuous phase tracking throughout the frequency range, while children showed significantly worse tracking at both high and low modulation frequencies. Adult and child transfer functions also differed significantly in their preferred modulation frequencies, and hemispheric asymmetries. These results are the first to describe the auditory temporal modulation transfer function in preschool children. They show that the immature brain differs markedly from the adult brain in its capacity to encode temporal information in sounds. These results must be accounted for by neurolinguistic theories that emphasize the role of specific temporal modulation frequencies for the neural encoding of speech. Keywords: Auditory Perception, Brain Mapping, Language, Magnetoencephalography, Brain Development Conference: XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014. Presentation Type: Poster Topic: Language Citation: Tang H, Brock J, Crain S and Johnson B (2015). Auditory envelope following responses in the mature and developing human brain. Conference Abstract: XII International Conference on Cognitive Neuroscience (ICON-XII). doi: 10.3389/conf.fnhum.2015.217.00363 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2015; Published Online: 24 Apr 2015. * Correspondence: Ms. Huizhen Tang, Macquarie University, Cognitive Science, North Ryde, Australia, joann.tang@mq.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Huizhen Tang Jon Brock Stephen Crain Blake Johnson Google Huizhen Tang Jon Brock Stephen Crain Blake Johnson Google Scholar Huizhen Tang Jon Brock Stephen Crain Blake Johnson PubMed Huizhen Tang Jon Brock Stephen Crain Blake Johnson Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

The influence of inhibitory skill on phonological representations in production and perception☆

Inhibition is known to play a role in speech perception and has been hypothesized to likewise influence speech production. In this paper we test whether individual differences in inhibitory skill can lead to individual differences in phonological representations in perception and production. We further examine whether the type of inhibition that influences phonological representation is domain-specific or domain-general. Native French speakers read aloud sentences with words containing a voiced stop that either have a voicing neighbor (target) or not (control). The duration of pre-voicing was measured. Participants similarly performed a lexical decision task on versions of these target and matched control words whose pre-voicing duration was manipulated. Lastly, participants performed linguistic and non-linguistic inhibition tasks. Results indicate that the lower speakers' linguistic or non-linguistic inhibition is, the easier it is for them to recognize words with a voiceless neighbor when these words have a shorter, intermediate, pre-voicing rather than a longer one. Inhibitory skill did not predict recognition time for control words, indicating that the effect was due to the greater activation of the voiceless neighbor. Inhibition did not predict pre-voicing duration in production. These results indicate that individual differences in cognitive skills can influence phonological representations in speech perception.

Vowel production in sighted children and congenitally blind children

It is well known that vision plays an important role in speech perception. At the production level, we have recently shown that speakers with congenital visual deprivation produce smaller displacements of the lips (visible articulator) compared to their sighted peers [L. Ménard, C. Toupin, S. Baum, S. Drouin, J. Aubin, and M. Tiede, J. Acoust. Soc. Am. 134, 2975–2987 (2013)]. To further investigate the impact of visual experience on the articulatory gestures used to produce intelligible speech, a speech production study was conducted with blind and sighted school-aged children. Eight congenitally blind children (mean age: 7 years old, from 5 years to 11 years) and eight sighted children (mean age: 7 years old, from 5 years to 11 years) were recorded using a synchronous ultrasound and Optotrak imaging system to record tongue and lip positions. Repetitions of the French vowels /i/, /a/, and /u/ were elicited in a /bVb/ sequence in two prosodic conditions: neutraland under contrastive focus. Tongue contours, lip positions, and formant values were extracted. Acoustic data show that focused syllables are less differentiated from their unfocused counterparts in blind children than in sighted children. Trade-offs between lip and tongue positions are examined.

Interaction between auditory and motor systems in speech perception

Based on the Motor Theory of speech perception, the interaction between the auditory and motor systems plays an essential role in speech perception. Since the Motor Theory was proposed, it has received remarkable attention in the field. However, each of the three hypotheses of the theory still needs further verification. In this review, we focus on how the auditory-motor anatomical and functional associations play a role in speech perception and discuss why previous studies could not reach an agreement and particularly whether the motor system involvement in speech perception is task-load dependent. Finally, we suggest that the function of the auditory-motor link is particularly useful for speech perception under adverse listening conditions and the further revised Motor Theory is a potential solution to the "cocktail-party" problem.

Spectral information in nonspeech contexts influences children’s categorization of ambiguous speech sounds

For both adults and children, acoustic context plays an important role in speech perception. For adults, both speech and nonspeech acoustic contexts influence perception of subsequent speech items, consistent with the argument that effects of context are due to domain-general auditory processes. However, prior research examining the effects of context on children’s speech perception have focused on speech contexts; nonspeech contexts have not been explored previously. To better understand the developmental progression of children’s use of contexts in speech perception and the mechanisms underlying that development, we created a novel experimental paradigm testing 5-year-old children’s speech perception in several acoustic contexts. The results demonstrated that nonspeech context influences children’s speech perception, consistent with claims that context effects arise from general auditory system properties rather than speech-specific mechanisms. This supports theoretical accounts of language development suggesting that domain-general processes play a role across the lifespan.

Shared and distinct neural correlates of vowel perception and production

Recent neurobiological models postulate that sensorimotor interactions play a key role in speech perception and speech motor control, especially under adverse listening conditions or in case of complex articulatory speech sequences. The present fMRI study aimed to investigate whether isolated vowel perception and production might also induce sensorimotor activity, independently of syllable sequencing and coarticulation mechanisms and using a sparse acquisition technique in order to limit influence of scanner noise. To this aim, participants first passively listened to French vowels previously recorded from their own voice. In a subsequent production task, done within the same imaging session and using the same acquisition parameters, participants were asked to overtly produce the same vowels. Our results demonstrate that a left postero-dorsal stream, linking auditory speech percepts with articulatory representations and including the posterior inferior frontal gyrus, the adjacent ventral premotor cortex and the temporoparietal junction, is an influential part of both vowel perception and production. Specific analyses on phonetic features further confirmed the involvement of the left postero-dorsal stream in vowel processing and motor control. Altogether, these results suggest that vowel representations are largely distributed over sensorimotor brain areas and provide further evidence for a functional coupling between speech perception and production systems. ► Sparse sampling fMRI study of vowel perception and production. ► Implication of a left postero-dorsal stream in both vowel perception and production. ► Vowel representations distributed over sensorimotor brain areas. ► Support for a close relationship between speech perception and production.

Utility of TMS to understand the neurobiology of speech

According to a traditional view, speech perception and production are processed largely separately in sensory and motor brain areas. Recent psycholinguistic and neuroimaging studies provide novel evidence that the sensory and motor systems dynamically interact in speech processing, by demonstrating that speech perception and imitation share regional brain activations. However, the exact nature and mechanisms of these sensorimotor interactions are not completely understood yet. Transcranial magnetic stimulation (TMS) has often been used in the cognitive neurosciences, including speech research, as a complementary technique to behavioral and neuroimaging studies. Here we provide an up-to-date review focusing on TMS studies that explored speech perception and imitation. Single-pulse TMS of the primary motor cortex (M1) demonstrated a speech specific and somatotopically specific increase of excitability of the M1 lip area during speech perception (listening to speech or lip reading). A paired-coil TMS approach showed increases in effective connectivity from brain regions that are involved in speech processing to the M1 lip area when listening to speech. TMS in virtual lesion mode applied to speech processing areas modulated performance of phonological recognition and imitation of perceived speech. In summary, TMS is an innovative tool to investigate processing of speech perception and imitation. TMS studies have provided strong evidence that the sensory system is critically involved in mapping sensory input onto motor output and that the motor system plays an important role in speech perception.