The distribution of wavelength and orientation selective cells in different areas of monkey visual cortex.

The distribution of orientation and wavelength selective cells in visual areas V1, the V4 complex and V5 of macaque monkey cortex was studied by recording from regions representing equivalent eccentricities in each and characterizing cells for their orientational and wavelength preferences. The results showed: (a) that in V1 wavelength selective cells are concentrated in the region of foveal representation (central 0-2 degrees) and decline at increasing eccentricities; (b) that in the V4 complex the concentration of such cells does not vary with eccentricity; rather, there are regional variations that are not eccentricity dependent but follow other, and unknown, rules; (c) that in V5 there are virtually no wavelength selective cells even at central eccentricities; (d) that in V1 fewer than 50% of cells with receptive fields in the central 0-2 degrees are orientation selective and that the proportion of such cells increases to reach a high of about 80% at eccentricities of between 10 and 30 degrees; (e) that in the V4 complex and in V5 the concentration of orientation selective cells decreases at increasing eccentricities; (f) that very few wavelength selective cells in V1 and in the V4 complex are orientation selective. The implications of these findings for a comparison between visual areas of the monkey cortex are discussed.