Norma Graham

Norma Graham

Ph.D., University of Pennsylvania, 1970

General Area of Research

Visual perception, human psychophysics, mathematical models of visual behavior and neurophysiology

Current Research

Mathematical Models Of Visual Processes.Visual processing requires 25-40% of the human brain's tissue, but we understand very little of it. In our lab, we are interested in intermediate levels of visual processing: levels which are lower than the perception of "objects” and "scenes" but higher than the pointwise processing of the retina. (The terms "lower" and "higher" are only approximate, of course, since information travels "downstream" as well as "upstream".) These intermediate processes presumably have their neural substrate in the cortical areas V1 to V4/MT. The approach that we have been using to study these intermediate levels is to build on the field's accumulated knowledge of multiple analyzers selectively sensitive to spatial frequency, orientation, spatial position, direction of motion, etc. We use mathematical models to interpret data from behavioral studies (some done by us) and neurophysiological studies (usually done by others) of visual perception. We have been particularly interested in four visual processes: light adaptation, multiple analyzers like spatial-frequency channels, complex or second-order channels, and contrast normalization. We are also interested in the problem of adequately characterizing the "decision stage" (the assumptions that link the outputs of the visual processes under study to the responses of the observers in the behavioral experiments).For a more complete description of these and other research projects please visit the Research Lab Site

Courses Taught

Selected Publications

Two visual contrast processes: One new, one old.

Graham, Norma
Wolfson, S.
Sabina Chubb,
Charles (Ed)
Dosher, Barbara A. (Ed)
Lu, Zhong-Lin (Ed)
Shiffrin, Richard M. (Ed)

Beyond multiple pattern analyzers modeled as linear filters (as classical V1 simple cells): useful additions of the last 25 years.

Graham NV