This paper demonstrates that much of visual motion coding in primary visual cortex can beunderstood from a theory of efficient motion coding in the multiscale representation. The theory predicts that cortical cells can have a spectrum of directional indices, be tuned to different directions of motion, and have spatio-temporally separable or inseparable receptive fields (RF). The predictions also include the following correlations between motion coding and spatial, chromatic, and stereo codings: the preferred speed is larger when the cell receptive field size is larger, the color channel prefers smaller speed than the luminance channel, and both the optimal speeds and the preferred directions of motion can be different for inputs from different eyes to the same neuron. These predictions agree with experimental observations. In addition, this theory makes predictions that have not been experimentally investigated systematically and provides testing ground for the efficient multiscale coding framework. These predictions are: (1) if nearby cortical cells of a given preferred orientation and scale prefer opposite directions of motion and have quadrature RF phase relationship with each other, then they will have the same directional index; (2) a single neuron can have different optimal motion speeds for opposite motion directions of monocular stimuli, and (3) a neuron's ocular dominance may change with motion direction if the neuron prefers opposite directions for inputs from different eyes.
Published in Neural Computation vol. 8, no.4, p705-30, May, 1996