The proposed research focuses on the sensory part of this transformation. Namely, how does the visual system process the optic flow that occurs during self-motion in a way that could be useful for guiding navigation? The applicant, Christopher Pack, is currently a Ph.D. candidate with Professor Stephen Grossberg and Professor Ennio Mingolla in the Department of Cognitive and Neural Systems at Boston University. His dissertation research has employed quantitative modeling methods and psychophysical techniques to probe the neural mechanisms underlying optic flow processing. However, the applicant's long-term goal is to establish a neurophysiological research program to study optic flow and eye movement processing in monkey cortex. The applicant's doctoral studies have provided a strong background in theoretical and psychophysical techniques. This background will be essential to the design and implementation of novel neurophysiological experiments. The facilities and instruction necessary to carry out these experiments will be provided by the sponsor, Dr. Richard Born.

The proposed research consists of a series of neurophysiological experiments. These experiments are motivated in part by a neural model developed and tested by the applicant, in collaboration with his mentors. The model quantitatively simulates a wide variety of seemingly paradoxical physiological results relating monkey cortical cell response properties to optic flow stimuli. Using the same parameters, the model qualitatively simulates human psychophysical results on the perception of self-motion direction. The proposed experiments will provide a test of the main model predictions, while gathering meaningful data on cortical processing of optic flow. One goal of the proposed experimental work is to relate cell properties in area MST to ecologically valid optic flow stimuli. This would serve as an important link in understanding how the visual system uses optic flow for navigation.

A second set of experiments would probe the mechanisms by which humans and primates combine visual and nonvisual sources of information. When the eyes move, the background sweeps across the retinal surface. In order to perceive a stable world, it is necessary to compensate in some way for the visual effects of eye movements. Otherwise, basic behaviors such as navigation and tracking of moving objects would be impossible. Analysis of psychophysical and physiological data suggests that the necessary compensation may take place in cortical area MT.

This proposal includes brief overviews of previous work on optic flow, heading perception, and data from cell recordings. The applicant's modeling work is presented briefly to provide some motivation for the proposed experiments. The experimental methods are also described. The planned experiments are the result of discussions with the sponsor during lab visits and phone conversations. Dr. Born is currently investigating motion perception and eye movement influences on areas MT and MST, making this collaboration appealing to him, as well as to the applicant.