Opponent‐colour cells in different layers of foveal striate cortex

The majority of cells in layer 4B have opponent-colour properties indicating that colour opponency plays an important role in the early stages of visual processing in foveal striate cortex. In contrast to cells in the lateral geniculate nucleus many of these cells receive centre-surround antagonism from the same cone mechanism. Some cells show this spatial antagonism at threshold; others require suprathreshold stimuli for its demonstration.2. The majority of cells in layer 4B do not show orientation or directional selectivity. The proportion of cells with orientation and directional selectivity increases and the proportion of opponent-colour cells decreases with increasing distance above and below layer 4B so that the majority of cells in the outer layers exhibit considerable spatial selectivity without apparent colour opponency. These changing proportions suggest that the latter cells may be receiving their inputs from different types of opponent-colour cells making them sensitive to different types of colour contrast but not to colour per se.3. More opponent-colour cells receive inputs from the red- and green- sensitive cone mechanisms than from the blue-sensitive one. This difference is more marked in layer 4B than 3B suggesting that the latter cortical layer may be more involved in colour vision than the former.