Ph.D Thesis

Ph.D StudentFurman Moran
SubjectA Neural Model for Motion Processing in the Visual Cortex
During Pursuit Eye Movements
DepartmentDepartment of Biomedical Engineering
Supervisor ASSOCIATE PROF. Moshe Gur


Pursuit eye movements occur whenever we follow a moving object with our eyes. During pursuit, the visual system transforms the visual information coming from the eyes to a world-centered reference frame. Physiological and psychophysical studies had shown that this transformation is achieved via integration of visual information arriving from the eyes, with an internal motor signal indicating eye movements. In the present study we constructed a physiologically based neural network model consisting of three layers of computational units, simulating V1, MT and MST. The units in the third layer, like some neurons in area middle-superior-temporal (MST), receive, in addition to visual input, an extra-retinal signal related to eye movements. The excitatory and inhibitory connections to the MST layer developed during an unsupervised training process. The resulting MST units represent a transformation from retinal to real-world centered coordinates. We compared the response properties of these units with physiology, studied their relation to the input connectivity patterns, and studied the sensitivity of the training process to various training parameters. Next, we studied a pursuit related perceptual phenomena: The alteration of the perceived path of a moving target during pursuit of a circularly moving target. We studied the phenomenon experimentally, with a greater number of subjects then in previous studies, and under various parameter values. We performed model simulations of the phenomenon, and showed that simulation results match a variety of related psychophysical findings. By analyzing the model simulations, the experimental results were explained in terms of underlying neuronal mechanisms. Finally, we used the model to address the fundamental controversy regarding the relative weight of the motor signal during pursuit.