MULTISENSORY PROCESSING IN ‘UNIMODAL’ NEURONS: EVIDENCE FOR SUBTHRESHOLD EXCITATORY CROSS-MODAL EFFECTS IN CAT VISUAL CORTEX
Poster Presentation

Brian Allman
Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine

M. Alex Meredith
Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine

     Abstract ID Number: 45
     Full text: Not available
     Last modified: March 14, 2006
     Presentation date: 06/20/2006 10:00 AM in Hamilton Building, Foyer
     (View Schedule)

Abstract
Most multisensory studies examine neurons that receive convergent excitatory inputs from different sensory modalities and consequently demonstrate multisensory integration. On the other hand, when multisensory convergence is not apparent, the multisensory capacities of seemingly ‘unimodal’ neurons often go unexamined. The present experiments tested the multisensory responses of ‘unimodal’ neurons in the well-known Posterolateral Lateral Suprasylvian (PLLS) visual area of the cat. A total of 204 visually-responsive neurons were presented separate- and combined-modality stimulation using natural visual and auditory cues. None of the neurons responded to auditory stimuli presented alone. When the visual and auditory stimuli were combined, 19% (39/204) showed a significant response increase. Furthermore, the overwhelming majority (82%; 167/204) of the neurons showed a combined response that was greater than that produced by visual stimulation alone, and this population response change was highly significant (paired ‘t’-test, p<0.0001). These data indicate that subthreshold excitatory effects can occur on apparently ‘unimodal’ neurons and that these response modulations are robust at the population level. Such subthreshold effects might more appropriately be considered as manifestations of multisensory processing than multisensory integration. Supported by NIH-NS39460.