Onset timing of audiovisual crossmodal activations in primary sensory cortices
Single Paper Presentation

Tommi Raij
MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Harvard Medical School, Charlestown, MA, USA

Jyrki Ahveninen
MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Harvard Medical School, Charlestown, MA, USA

Fa-Hsuan Lin
MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Harvard Medical School, Charlestown, MA, USA

Thomas Witzel
Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, USA

Iiro Jääskeläinen
Laboratory of Computational Engineering, Helsinki University of Technology, Espoo, Finland

Cherif Sahyoun
Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, USA

Christos Vasios
MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Harvard Medical School, Charlestown, MA, USA

Steven Stufflebeam
MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Harvard Medical School, Charlestown, MA, USA

Matti Hämäläinen
MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Harvard Medical School, Charlestown, MA, USA

John Belliveau
MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Harvard Medical School, Charlestown, MA, USA

     Abstract ID Number: 103
     Full text: Not available
     Last modified: March 26, 2007
     Presentation date: 07/06/2007 11:30 AM in Quad General Lecture Theatre
     (View Schedule)

Abstract
Recent research suggests a role for primary sensory areas in multisensory integration. To investigate timing of earliest crossmodal influences, we recorded magnetoencephalographic (MEG) responses in 8 healthy humans to 300-ms auditory noise bursts and visual checkerboard stimuli and measured the onset latency of neural activity from the sensors over primary auditory and visual cortices. The auditory cortices were activated by auditory stimuli at 28 and 26 ms and by visual stimuli at 74 and 62 ms in the left and right hemispheres, respectively. The visual cortex was activated by visual stimuli at 49 ms and by auditory stimuli at 65 ms. Hence, crossmodal activations in auditory cortex started 36-46 ms and in the visual cortex 16 ms later than modality-specific activations. Theoretically, crossmodal input could arrive at primary sensory areas through direct connections from central sensory pathways, or through crossmodal cortico-cortical connections, either directly or through audiovisual association cortices. The observed asymmetrical crossmodal timings reflect different sensory-specific onset latencies in the auditory and visual cortices, thus suggesting that the origin of the crossmodal activations is in the primary sensory cortices of the opposite modality, with conduction delays of 37-39 ms from auditory to visual cortex and of 13-25 ms from visual to auditory cortex.