title: Putative mechanisms mediating tolerance for audiovisual stimulus onset asynchrony.
abstract: Audiovisual (AV) speech perception is robust to temporal asynchronies between visual and auditory stimuli. We investigated the neural mechanisms that facilitate tolerance for audiovisual stimulus onset asynchrony (AVOA) with EEG. Individuals were presented with AV words that were asynchronous in onsets of voice and mouth movement and judged whether they were synchronous or not. Behaviorally, individuals tolerated (perceived as synchronous) longer AVOAs when mouth movement preceded the speech (V-A) stimuli than when the speech preceded mouth movement (A-V). Neurophysiologically, the P1-N1-P2 auditory evoked potentials (AEPs), time-locked to sound onsets and known to arise in and surrounding the primary auditory cortex (PAC), were smaller for the in-sync than the out-of-sync percepts. Spectral power of oscillatory activity in the beta band (14-30 Hz) following the AEPs was larger during the in-sync than out-of-sync perception for both A-V and V-A conditions. However, alpha power (8-14 Hz), also following AEPs, was larger for the in-sync than out-of-sync percepts only in the V-A condition. These results demonstrate that AVOA tolerance is enhanced by inhibiting low-level auditory activity (e.g., AEPs representing generators in and surrounding PAC) that code for acoustic onsets. By reducing sensitivity to acoustic onsets, visual-to-auditory onset mapping is weakened, allowing for greater AVOA tolerance. In contrast, beta and alpha results suggest the involvement of higher-level neural processes that may code for language cues (phonetic, lexical), selective attention, and binding of AV percepts, allowing for wider neural windows of temporal integration, i.e., greater AVOA tolerance.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, The Ohio State University, College of Medicine, Columbus, Ohio;
authors.forename: Jyoti
authors.initials: J
authors.lastname: Bhat
authors.affiliation: Center for Mind and Brain, University of California, Davis, California; Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California; and.
authors.forename: Lee M
authors.initials: LM
authors.lastname: Miller
authors.affiliation: Department of Psychology, The Ohio State University, Columbus, Ohio.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Pitt
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, The Ohio State University, College of Medicine, Columbus, Ohio; Center for Mind and Brain, University of California, Davis, California; ajshahin@ucdavis.edu.
authors.forename: Antoine J
authors.initials: AJ
authors.lastname: Shahin
mesh_terms: D000161:Acoustic Stimulation; D000513:Alpha Rhythm; D001303:Auditory Cortex / Q000502:physiology*; D001307:Auditory Perception; D001611:Beta Rhythm; D003344:Cortical Synchronization; D005072:Evoked Potentials, Auditory; D005260:Female; D006801:Humans; D008297:Male; D009055:Mouth / Q000502:physiology; D009068:Movement; D010775:Photic Stimulation; D013067:Speech Perception; D014796:Visual Perception; D014831:Voice; D055815:Young Adult
keywords: EEG; alpha band activity; audiovisual stimulus onset asynchrony; auditory evoked potentials; beta band activity; oscillatory activity