Probability-based multisensory object formation: Rethinking cortical principles of sensory integration.
Multiple Paper Presentation

John J. Foxe
City College of New York

     Abstract ID Number: 125
     Last modified: June 1, 2007
     Presentation date: 07/06/2007 2:00 PM in Quad General Lecture Theatre
     (View Schedule)

Abstract
I will describe a multisensory illusion whereby fully unambiguous auditory motion direction can be completely reversed by simultaneous visual apparent motion stimuli. Audio-visual perceptual studies of apparent motion have traditionally used spatially coincident auditory and visual presentations; a constraint that seriously deteriorates the quality of visual apparent motion stimuli. That is, visual apparent motion is comparatively weak when induced by relatively distant and spatially isolated LEDs, the stimulus set-up of choice. Recent neurophysiological findings, however, have shown that early cortical multisensory processing occurs even when the elements of a multisensory event are spatially disparate. On this basis, we reasoned that by relaxing the spatial constraint, thereby allowing the use of much more compelling visual apparent motion stimuli, we could produce considerably stronger multisensory apparent motion biasing effects. Auditory stimuli were separated by the greatest possible spatial angle (i.e., 180°), whereas visual stimuli were only separated by 1.6°. If spatial alignment were critical, this arrangement would be expected to eliminate all cross-sensory perceptual effects. Alternately, if cortical sensory integrations are predicated on learned probabilities regarding the various properties of multisensory stimuli, then cross-sensory perceptual effects should be stronger due to the more compelling visual apparent motion stimuli. The latter was strongly the case with very robust illusory effects observed. We conclude that multisensory perceptual processing is probability-based, developing through environmental exposure, which cannot be fully characterized in terms of simple rule-based models.

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
• Arnaud Falchier
  Nathan Kline Institute
  Anatomical networks and physiological mechanisms of multisensory integration in macaque auditory cortex