The Journal of Neuroscience, January 1, 1998, 18(1):531-547
A Model for Encoding Multiple Object Motions and Self-Motion in
Area MST of Primate Visual Cortex
Richard S.
Zemel1 and
Terrence J.
Sejnowski2
1 Howard Hughes Medical Institute, Salk Institute for
Biological Studies, San Diego, California 92186-5800, and
2 Department of Biology, University of California, San
Diego, La Jolla, California 92093
Many cells in the dorsal part of the medial superior temporal (MST)
region of visual cortex respond selectively to specific combinations of
expansion/contraction, translation, and rotation motions. Previous
investigators have suggested that these cells may respond selectively
to the flow fields generated by self-motion of an observer. These
patterns can also be generated by the relative motion between an
observer and a particular object. We explored a neurally constrained
model based on the hypothesis that neurons in MST partially segment the
motion fields generated by several independently moving objects. Inputs
to the model were generated from sequences of ray-traced images that
simulated realistic motion situations, combining observer motion, eye
movements, and independent object motions. The input representation was
based on the response properties of neurons in the middle temporal area
(MT), which provides the primary input to area MST. After applying an
unsupervised optimization technique, the units became tuned to patterns
signaling coherent motion, matching many of the known properties of MST cells. The results of this model are consistent with recent studies indicating that MST cells primarily encode information concerning the
relative three-dimensional motion between objects and the observer.
Key words:
visual cortex; motion processing; motion segmentation; neural coding; area MST; heading detection; network model; flow field
analysis
Copyright © 1998 Society for Neuroscience 0270-6474/98/181531-17$05.00/0