Oxyopia Abstract

February 1, 2002
Noon
489 Minor Hall

Anthony Truchard, PhD
Vision Science Program, University of Califiornia, Berkeley
Host: Ralph Freeman

Title

"The contribution of contrast gain control to binocular interactions and temporal encoding of neurons in primary visual cortex"

Abstract

To be effective, a visual system must cope with variations in the contrast level of its input signals. In this talk, I will discuss some aspects of this problem that I have looked into as a graduate student here at U.C. Berkeley.

First, I describe the contribution of contrast gain control to responses of binocular simple cells of visual cortex. The experimental results indicate that control gain control occurs primarily before the signals from the two eyes have been combined by the brain. This points to a major contribution of early, monocular stages of visual processing to contrast gain control.

Second, I re-examine the issue of whether the spatiotemporal energy detector (Adelson and Bergen, 1985) is a suitable model for motion detection by visual neurons. An analysis involving a novel noise stimulus indicates that while directionally selective complex cells share some properties in common with the energy detector, they also exhibit a rapid contrast-dependent suppression effect. This suppression effect, seen in both simple and complex cells, is expected to improve response selectivity and to help achieve contrast gain control.

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