title: fMRI-Guided transcranial magnetic stimulation reveals that the superior temporal sulcus is a cortical locus of the McGurk effect.
abstract: 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. 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. We hypothesized that the STS plays a critical role in the creation of the McGurk percept. 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. 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. 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. 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. These results demonstrate that the STS plays a critical role in the McGurk effect and auditory-visual integration of speech.
authors.affiliation: Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, Texas 77030, USA. Michael.S.Beauchamp@uth.tmc.edu
authors.forename: Michael S
authors.initials: MS
authors.lastname: Beauchamp
authors.forename: Audrey R
authors.initials: AR
authors.lastname: Nath
authors.forename: Siavash
authors.initials: S
authors.lastname: Pasalar
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D001931:Brain Mapping; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation / Q000379:methods; D011601:Psychophysics; D011930:Reaction Time / Q000502:physiology; D012660:Semantics; D013067:Speech Perception / Q000502:physiology*; D013702:Temporal Lobe / Q000098:blood supply* / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
chemical_list: D010100:Oxygen