Anatomical networks and physiological mechanisms of multisensory integration in macaque auditory cortex
Multiple Paper Presentation

Arnaud Falchier
Nathan Kline Institute

     Abstract ID Number: 126
     Last modified: June 1, 2007
     Presentation date: 07/06/2007 2:00 PM in Quad General Lecture Theatre
     (View Schedule)

Abstract
Until recently, it was believed that multisensory integration occurs mainly in higher order cortical association areas. Over the past years a growing number of studies emphasized the role of low level unisensory areas in multisensory integration. We developed a multidisciplinary approach to investigate both the structure of cortical networks and the physiological processes supporting multisensory integration in macaque auditory cortex. Analysis of the anatomic circuits underlying multisensory convergence is accomplished with orthograde and retrograde tracers placed by microinjection into cortical sites identified by physiological measurements. To analyze the dynamics of multisensory interactions enabled by these connections, we recorded laminar field potential profiles (with derived current source density or CSD measures), along with the concomitant profile of action potentials, using linear array multielectrodes. We will present a quantitative description of anatomical projections afferent to auditory cortex that could support multisensory integration. Of particular interest are our new findings showing direct projections from visual area V2 and Prostriata to belt and parabelt areas of auditory cortex. In addition we will present a detailed description of physiological mechanisms of somatosensory-auditory interaction in primary auditory cortex (A1). The findings in A1 contrast with those from surrounding auditory association areas. The essence of this contrast is that: 1) the association areas display classic excitatory multisensory convergence and interaction, much like that seen in other cortical and subcortical regions, while 2) primary cortical area A1 displays a modulatory type of multisensory interaction never before observed. In this case the non-auditory input by itself causes no significant excitation. Rather, it resets ongoing oscillatory activity so that the accompanying auditory input arrives while the local neuronal ensemble is in a high excitability phase, and is thus amplified. This novel type of interaction, may serve as a model for understanding how multisensory interactions occur in low level, putatively unisensory cortical areas.

To be Presented at the Following Symposium:
Multisensory integration: Evidence from human and non-human primate studies
Other papers in this Symposium:

• Sophie Molholm
  Nathan Kline Institute for Psychiatric Research
  The Multisensory Nature of Object-Based Attention
• John J. Foxe
  City College of New York
  Probability-based multisensory object formation: Rethinking cortical principles of sensory integration.