Event-Related Potentials Associated with Somatosensory Effect in Audio-Visual Speech Perception

Somatosensory contribution to audio-visual speech processing

Audio–visual congruency alters power and coherence of oscillatory activity within and between cortical areas

The contribution of dynamic visual cues to audiovisual speech perception

Effects of noise and noise reduction on audiovisual speech perception in cochlear implant users: An ERP study

The present study investigated the impact of Chinese dialects on McGurk effect using behavioral and event-related potential (ERP) methodologies. Specifically, intra-language comparison of McGurk effect was conducted between Mandarin and Cantonese speakers. The behavioral results showed that Cantonese speakers exhibited a stronger McGurk effect in audiovisual speech perception compared to Mandarin speakers, although both groups performed equally in the auditory and visual conditions. ERP results revealed that Cantonese speakers were more sensitive to visual cues than Mandarin speakers, though this was not the case for the auditory cues. Taken together, the current findings suggest that the McGurk effect generated by Chinese speakers is mainly influenced by segmental phonology during audiovisual speech integration.

In audiovisual speech perception, visual information from a talker's face during mouth articulation is available before the onset of the corresponding audio speech, and thereby allows the perceiver to use visual information to predict the upcoming audio. This prediction from phonetically congruent visual information modulates audiovisual speech perception and leads to a decrease in N1 and P2 amplitudes and latencies compared to the perception of audio speech alone. Whether audiovisual experience, such as with musical training, influences this prediction is unclear, but if so, may explain some of the variations observed in previous research. The current study addresses whether audiovisual speech perception is affected by musical training, first assessing N1 and P2 event-related potentials (ERPs) and in addition, inter-trial phase coherence (ITPC). Musicians and non-musicians are presented the syllable, /ba/ in audio only (AO), video only (VO), and audiovisual (AV) conditions. With the predictory effect of mouth movement isolated from the AV speech (AV−VO), results showed that, compared to audio speech, both groups have a lower N1 latency and P2 amplitude and latency. Moreover, they also showed lower ITPCs in the delta, theta, and beta bands in audiovisual speech perception. However, musicians showed significant suppression of N1 amplitude and desynchronization in the alpha band in audiovisual speech, not present for non-musicians. Collectively, the current findings indicate that early sensory processing can be modified by musical experience, which in turn can explain some of the variations in previous AV speech perception research.

To investigate the nature of facial information involved in the integration of audiovisual speech perception, we examined the influence of facial views on the McGurk effect under two auditory conditions. While the speech perception of most of the audiovisual syllables used was little affected by the facial views and the auditory noise, a stronger McGurk effect was obtained for the 3/4-view image uttering labial sounds presented with auditory syllables of alveolars under the auditory noise. However, the facial view did not affect the visual identification of labials in the same way. These results suggest that the information about labial or nonlabial is not the only facial information involved in the McGurk effect. It appears some other information available only in the 3/4-view image might also be involved in the McGurk effect. Implications for the processing of visual, auditory and audiovisual speech are discussed.

Speech comprehension is improved by viewing a speaker's face, especially in adverse hearing conditions, a principle known as inverse effectiveness. However, the neural mechanisms that help to optimize how we integrate auditory and visual speech in such suboptimal conversational environments are not yet fully understood. Using human EEG recordings, we examined how visual speech enhances the cortical representation of auditory speech at a signal-to-noise ratio that maximized the perceptual benefit conferred by multisensory processing relative to unisensory processing. We found that the influence of visual input on the neural tracking of the audio speech signal was significantly greater in noisy than in quiet listening conditions, consistent with the principle of inverse effectiveness. Although envelope tracking during audio-only speech was greatly reduced by background noise at an early processing stage, it was markedly restored by the addition of visual speech input. In background noise, multisensory integration occurred at much lower frequencies and was shown to predict the multisensory gain in behavioral performance at a time lag of ∼250 ms. Critically, we demonstrated that inverse effectiveness, in the context of natural audiovisual (AV) speech processing, relies on crossmodal integration over long temporal windows. Our findings suggest that disparate integration mechanisms contribute to the efficient processing of AV speech in background noise. The behavioral benefit of seeing a speaker's face during conversation is especially pronounced in challenging listening environments. However, the neural mechanisms underlying this phenomenon, known as inverse effectiveness, have not yet been established. Here, we examine this in the human brain using natural speech-in-noise stimuli that were designed specifically to maximize the behavioral benefit of audiovisual (AV) speech. We find that this benefit arises from our ability to integrate multimodal information over longer periods of time. Our data also suggest that the addition of visual speech restores early tracking of the acoustic speech signal during excessive background noise. These findings support and extend current mechanistic perspectives on AV speech perception.

The McGurk effect, which denotes the influence of visual information on audiovisual speech perception, is less frequently observed in individuals with autism spectrum disorder (ASD) compared to those without it; the reason for this remains unclear. Several studies have suggested that facial configuration context might play a role in this difference. More specifically, people with ASD show a local processing bias for faces-that is, they process global face information to a lesser extent. This study examined the role of facial configuration context in the McGurk effect in 46 healthy students. Adopting an analogue approach using the Autism-Spectrum Quotient (AQ), we sought to determine whether this facial configuration context is crucial to previously observed reductions in the McGurk effect in people with ASD. Lip-reading and audiovisual syllable identification tasks were assessed via presentation of upright normal, inverted normal, upright Thatcher-type, and inverted Thatcher-type faces. When the Thatcher-type face was presented, perceivers were found to be sensitive to the misoriented facial characteristics, causing them to perceive a weaker McGurk effect than when the normal face was presented (this is known as the McThatcher effect). Additionally, the McGurk effect was weaker in individuals with high AQ scores than in those with low AQ scores in the incongruent audiovisual condition, regardless of their ability to read lips or process facial configuration contexts. Our findings, therefore, do not support the assumption that individuals with ASD show a weaker McGurk effect due to a difficulty in processing facial configuration context.

The McGurk effect, an incongruent pairing of visual /ga/–acoustic /ba/, creates a fusion illusion /da/ and is the cornerstone of research in audiovisual speech perception. Combination illusions occur given reversal of the input modalities—auditory /ga/-visual /ba/, and percept /bga/. A robust literature shows that fusion illusions in an oddball paradigm evoke a mismatch negativity (MMN) in the auditory cortex, in absence of changes to acoustic stimuli. We compared fusion and combination illusions in a passive oddball paradigm to further examine the influence of visual and auditory aspects of incongruent speech stimuli on the audiovisual MMN. Participants viewed videos under two audiovisual illusion conditions: fusion with visual aspect of the stimulus changing, and combination with auditory aspect of the stimulus changing, as well as two unimodal auditory- and visual-only conditions. Fusion and combination deviants exerted similar influence in generating congruency predictions with significant differences between standards and deviants in the N100 time window. Presence of the MMN in early and late time windows differentiated fusion from combination deviants. When the visual signal changes, a new percept is created, but when the visual is held constant and the auditory changes, the response is suppressed, evoking a later MMN. In alignment with models of predictive processing in audiovisual speech perception, we interpreted our results to indicate that visual information can both predict and suppress auditory speech perception.

The "McGurk effect" demonstrates that visual (lip-read) information is used during speech perception even when it is discrepant with auditory information. While this has been established as a robust effect in subjects from Western cultures, our own earlier results had suggested that Japanese subjects use visual information much less than American subjects do (Sekiyama & Tohkura, 1993). The present study examined whether Chinese subjects would also show a reduced McGurk effect due to their cultural similarities with the Japanese. The subjects were 14 native speakers of Chinese living in Japan. Stimuli consisted of 10 syllable (/ba/, /pa/, /ma/, /wa/, /da/, /ta/, /na/, /ga/, /ka/, /ra/) pronounced by two speakers, one Japanese and one American. Each auditory syllable was dubbed onto every, visual syllable within one speaker, resulting in 100 audiovisual stimuli in each language. The subjects' main task was to report what they thought they had heard while looking at and listening to the speaker while the stimuli were being uttered. Compared with previous results obtained with American subjects, the Chinese subjects showed a weaker McGurk effect. The results also showed that the magnitude of the McGurk effect depends on the length of time the Chinese subjects had lived in Japan. Factors that foster and alter the Chinese subjects' reliance on auditory information are discussed.

Multisensory convergence and integration in the neostriatum and globus pallidus of the rat

Introduction to dual sensory loss issue.

Noise alters beta-band activity in superior temporal cortex during audiovisual speech processing

Audiovisual perception of gemination and pharyngealization in Arabic