However, neuroimaging studies that have compared incongruent auditory–visual speech, including McGurk syllables, to congruent speech or other baselines have reported differences in a broad network of brain regions in addition to the STS, including the supramarginal gyrus ( Jones and Callan, 2003 Bernstein et al., 2008), the inferior parietal lobule ( Jones and Callan, 2003), the precentral gyrus ( Jones and Callan, 2003), the superior frontal gyrus ( Miller and D'Esposito, 2005), Heschl's gyrus ( Miller and D'Esposito, 2005), and the middle temporal gyrus ( Callan et al., 2004). The superior temporal sulcus (STS) has been implicated in auditory–visual multisensory integration for both speech and nonspeech stimuli ( Calvert et al., 2000 Sekiyama et al., 2003 Beauchamp, 2005a Miller and D'Esposito, 2005). These results demonstrate that the STS plays a critical role in the McGurk effect and auditory–visual integration of speech.Ī textbook example of how both the auditory and visual modalities are important for speech perception is the McGurk effect, in which an auditory syllable (phoneme) is perceived very differently depending on whether it is accompanied by a visual movie of a speaker pronouncing the same syllable or a different, incongruent syllable ( McGurk and MacDonald, 1976). TMS of the STS was effective at disrupting the McGurk effect only in a narrow temporal window from 100 ms before auditory syllable onset to 100 ms after onset, and TMS of a control location did not influence perception of McGurk or control stimuli. Across three experiments, TMS of the STS significantly reduced the likelihood of the McGurk percept but did not interfere with perception of non-McGurk stimuli. Then, activity in this region of the STS was disrupted with single-pulse transcranial magnetic stimulation (TMS) as subjects rated their percept of McGurk and non-McGurk stimuli. Because the location of multisensory integration in the STS varies from subject to subject, the location of auditory–visual speech processing in the STS was first identified in each subject with fMRI. We hypothesized that the STS plays a critical role in the creation of the McGurk percept. Anatomical and physiological studies in human and nonhuman primates have suggested that the superior temporal sulcus (STS) is involved in auditory–visual integration for both speech and nonspeech stimuli. A compelling example of auditory–visual multisensory integration is the McGurk effect, in which an auditory syllable is perceived very differently depending on whether it is accompanied by a visual movie of a speaker pronouncing the same syllable or a different, incongruent syllable.
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