From Markov random field theory to the neural circuitry of striate visual cortex

The consensus is that virtually all aspects of the response selectivity exhibited by visual cortical cells are either created of sharpened by intra-cortical inhibitory cells. There is abundant experimental evidence supporting the view that the inhibitory cortical cells are orientation specific. To understand the mechanism underlying the orientation specificity of inhibitory cortical cells is a key to understand the neural circuitry of the striate visual cortex. It is the purpose of this article to show how such an orientation-specific inhibition can be achieved from the striate-cortex innervating nonoriented lateral geniculate cells. A computational model for the orientation-specific inhibition is introduced. The model consists of three parts: (a) a two-layered hierarchical Markov random field; (b) a computational goal formulated based on the maximum a posteriori estimation principle; (c) a deterministic parallel algorithm to achieve the computational goal. A physiologically-plausible firing-rate-coded neural circuit is introduced to implement the computational model.