Visual motion is processed by neurons in primary visual cortex that are sensitive to spatial orientation and speed. Many models of local velocity computation are based on a second stage that pools the outputs of first-stage neurons selective for different orientation, but the nature of this pooling remains controversial. In a human psychophysical detection experiment, we found near-perfect summation of image energy when it was distributed uniformly across all orientations, but poor summation when it was concentrated in specific orientation bands. The data are consistent with a model that integrates uniformly over all orientations, even when this strategy is sub-optimal.
Bibliographical noteFunding Information:
P.S. was supported by an NIH training grant, D.C.K. was supported by a grant from the NIH and E.P.S. was supported by a Sloan Fellowship, an NSF CAREER grant and the Sloan Program in Theoretical Neurobiology at New York University.