Poster E108, Monday, March 27, 2:30 – 4:30 pm, Pacific Concourse
The “temporal synchrony” method for identifying multisensory brain regions using fMRI
W. Dale Stevens1, Stephanie M. Lavoie1, Ryan A. Stevenson2, Morgan D. Barense3, Mark T. Wallace4, James M. Bebko1; 1York University, 2University of Western Ontario, 3University of Toronto, 4Vanderbilt University
Multisensory perception is integral to cognitive, language, and social development and functioning. The posterior superior temporal sulcus (pSTS) plays a critical role in auditory-visual (AV) integration. Several criteria used for identifying putative AV-multisensory regions with fMRI include higher activation for AV-multisensory stimuli than the 1) mean activation for unisensory auditory and visual stimuli (“mean” method); 2) maximum activation for unisensory auditory and visual stimuli (“max” method); 3) summed activation for unisensory auditory and visual stimuli (“super-additivity” method). Only the super-additivity method accounts for known population-level neural responses of multisensory neurons; however, it has not proven to be empirically tenable, as previous work failed to reliably identify pSTS regions using this method. A known property of multisensory neurons is a greater response to temporally synchronous than asynchronous stimuli. Here, a novel “temporal synchrony” method, identifying brain regions that show higher activation for temporally synchronous than asynchronous AV-multisensory stimuli, was compared to previous methods using fMRI with 17 healthy young adults. Participants were presented with video clips of temporally synchronous and asynchronous social-linguistic, social non-linguistic, and non-social/non-linguistic stimuli. Collapsed across content conditions, the temporal synchrony method identified a pSTS region in more participants than all previous methods. Within individually-defined pSTS regions across participants, the temporal synchrony criterion was met in all individual content conditions, while the super-additivity criterion was not met in any. Our results demonstrate that the temporal synchrony method is more theoretically valid and empirically tenable than previously used methods. We recommend its application in future studies of multisensory perception.
Topic Area: PERCEPTION & ACTION: Multisensory