Auditory-visual Multisensory Interactions Modulate the Dynamics of BOLD Responses in Unisensory Cortices
Poster Presentation

Roberto Martuzzi
Department of Radiology, University Hospital, Lausanne, SWITZERLAND

Micah Murray
Division of Neuropsychology, University Hospital, Lausanne, SWITZERLAND

Christoph Michel
Department of Neuroscience, University of Geneva, Geneva, SWITZERLAND

Philippe Maeder
Department of Radiology, University Hospital, Lausanne, SWITZERLAND

Jean-Philippe Thiran
Signal Processing Institute, EPFL, Lausanne, SWITZERLAND

Stephanie Clarke
3Division of Neuropsychology, University Hospital, Lausanne, SWITZERLAND

Reto Meuli
Department of Radiology, University Hospital, Lausanne, SWITZERLAND

     Abstract ID Number: 113
     Full text: Not available
     Last modified: March 21, 2005
     Presentation date: 06/07/2005 9:00 AM in MART Auditorium
     (View Schedule)

Abstract
Multisensory inputs improve performance, and interactions occur early after stimulus presentation. We used event-related fMRI to investigate the loci and BOLD dynamics of auditory-visual interactions. Ten subjects performed a simple reaction time task at 3T, with three randomly intermixed conditions: visual alone, auditory alone, and simultaneous auditory-visual stimulation. Stimuli were presented for 150ms with an inter-stimulus interval varying from 14.2-17.8s in steps of 200ms to estimate the BOLD dynamics. Reaction times were significantly faster for multisensory stimuli. BOLD responses within the left lingual gyrus (BA19) were stronger to multisensory stimuli than either other unisensory condition. The posterior part of the superior temporal gyrus bilaterally (BA22), the insula bilaterally (BA13), and motor-related areas (BA4/24) responded sub-linearly. Peak latencies of the BOLD signal in the left visual cortex (BA17) were significantly earlier for multisensory than either visual (p<0.05) or auditory (p<0.05) stimuli. In the left superior temporal gyrus (BA22), the multisensory BOLD response peaked earlier than the visual (p<0.05), with a tendency versus the auditory response (p<0.10). Peak latencies from auditory and visual conditions did not differ. These results provide evidence for multisensory interactions and BOLD dynamic modulations between auditory-visual stimuli within specific, low-level unisensory areas.