Directionally Selective Complex Cells and the Computation of Motion Energy in Cat Visual Cortex
Robert C. Emerson, James R. Bergen, and Edward H. Adelson
Vision Research, vol. 32, no. 2, pp. 203-218 (1992).
We applied a set of 1- and 2-bar tests to directionally selective (DS) complex cells in the cat's striate cortex, and
compared the responses with those predicted by two computational models. Single-bar responses and 2-bar interactions
produce distinctive patterns that are highly diagnostic. The observed responses are quite similar to those predicted
by a basic (non-opponent) motion-energy model [Adelson & Bergen (1985) Journal of the Optical Society of America A,
2, 284-299]. However, they are not consistent with an opponent combination of energy models, nor are they consistent
with any stage of the classic Reichardt model. In particular, the Reichardt model (as well as opponent combinations
of energy models) predicts a separable space-time symmetry in the 2-bar interaction that is not observed in our
measurements, while the non-opponent energy model predicts an inseparable, oriented interaction very similar to the
measured cortical responses. Comparisons between model and measurements suggest possible mechanisms of spatial
receptive-field organization and of nonlinear transformations.