Friday, March 31, 2017 3 p.m. to 4 p.m.

Resonances and patterns in the visual cortex

 

Professor Bard Ermentrou

Distinguished University Professor

Department of Mathematics

University of Pittsburgh

 

Abstract:  When subjects are exposed to full field flicker in certain frequencies, they perceive a variety of complex geometric patterns that are often called flicker hallucinations. On the other hand, when looking at high contrast geometric patterns like op art, shimmering and flickering is observed. In some people, flicker or such op art can induce seizures.  In this talk, I describe a simple network model of excitatory and inhibitory neurons that comprise the visual area of the brain. I show that these phenomena are reproduced and then give an explanation based on symmetry breaking bifurcations and Floquet theory. Symmetric bifurcation theory also shows why one expects a different class of patterns at high frequencies from those at low frequencies. Finally, I will describe some recent experimental verification of our ideas in a collaboration with some psychologists in Australia.

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Mathematical Sciences Building: 318

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