Orientation and color columns in monkey visual cortex.

The literature on orientation and color columns in monkey visual cortex is reviewed. The orientation column model most consistent with existing data is one containing 'stripes' of alternating positive and negative orientation 'singularities' (cytochrome oxidase blobs) which run along the centers of ocular dominance (OD) columns, with horizontal and vertical orientations alternating at interblob centers. Evidence is summarized suggesting that color is mapped continuously across the monkey's primary visual cortex, with the ends of the spectrum located at 'red' and 'blue' cytochrome oxidase blobs and extra-spectral purple located between adjacent red and blue blobs in the same OD column. In the orientation column model, the 'linear zones' of Obermayer and Blasdel have the appearance of the lines on a pumpkin. A pinwheel model of color columns, consistent with existing data, includes spectral and extra-spectral colors as spokes. Spectral iso-color lines run across iso-orientation lines in linear zones, while extra-spectral iso-color lines occupy the 'saddle points' of Obermayer and Blasdel. The color column model accounts for closure of the perceptual color circle, as proposed by Isaac Newton in 1704, but does not account for color opponency.