"Optimal integration of sensory evidence: Building blocks and canonical computations"
Mon, March 18, 2013 • 12:00 PM - 1:00 PM • SEA 4.244 (Library/Auditorium)
ABSTRACT: A fundamental aspect of our sensory experience is that information from different modalities is often seamlessly integrated into a unified percept. Recent computational and behavioral studies have shown that humans combine sensory cues according to a statically optimal scheme derived from Bayesian probability theory; they perform better when two sensory cues are combined. We have explored multisensory cue integration for self-motion (heading) perception using both visual (optic flow) and vestibular (linear acceleration) signals. A neural correlate of this interaction during a heading direction discrimination task is found in the activity of single neurons in the macaque visual cortex. Neurons with congruent heading preferences for visual and vestibular stimuli show improved sensitivity and lower neuronal thresholds under cue combination. In contrast, neurons with opposite preferences show diminished sensitivity under cue combination. Congruent neurons also show trial-by-trial re-weighting of visual and vestibular cues, as expected from optimal integration, and population responses can predict the main properties of perception. The trial-by-trial re-weighting can be easily simulated using a divisive normalization model extended to multisensory integration. Whereas congruent multisensory cells increase self-motion precision, oppositely-tuned multisensory cells are specialized for solving a fundamental ambiguity of the visual system, that of distinguishing motion of the objects around us versus our own motion through space. Deficits in behavior brought by chemical inactivation provide further support of the hypothesis that extrastriate visual cortex mediates multisensory integration for motion perception. These findings provide the first behavioral demonstration of statistically-optimal cue integration in non-human primates and identify both the computations and neuronal populations that may form its neural basis. Diseases, like autism spectrum disorders, might suffer from deficits in one or more of these canonical computations, which are fundamental in helping merge our senses to interpret and interact with the world.