High-density electrical mapping of mismatch negativity evoked by the McGurk illusion
Poster Presentation

Pierfilippo De Sanctis

Dave Saint-Amour

Sophie Molholm

Walter Ritter

John James Foxe

     Abstract ID Number: 148
     Full text: Not available
     Last modified: March 21, 2005

Abstract
Seeing a speaker’s articulatory gestures can affect speech perception, as illustrated by the McGurk effect, where dubbing an incongruent articulatory movement onto an auditory phoneme leads to an illusory auditory perception. It has been shown that the event-related potential, the Mismatch Negativity (MMN), can be evoked by the McGurk illusion. Since the auditory stimuli are invariant, the deviant elicited MMN has been interpreted as phonetic in nature. Here we investigated the putative hemispheric dominance of McGurk-MMN by recording high-density ERPs using an oddball paradigm in two conditions: visual alone (/ba/ “standard” and /va/ “deviant”) and audiovisual (audio /ba/ and visual /ba/ “standard” and /va/ “deviant”, illusory percept /va/). If the McGurk-MMN represents phonetic processing, then one would predict left hemisphere dominance. A McGurk-MMN was indeed found, indicating that audiovisual integration gave rise to the auditory deviant percept. Surprisingly, the topography of the McGurk-MMN showed a right hemispheric dominance, suggesting that this effect may not be based on a phonological trace but might rely on acoustical processing which involves the right hemisphere. Source-analysis localized the generator of this right hemisphere dominant MMN response to the superior temporal gyrus, a region well-known for its multisensory integration properties from imaging studies.