CHROMATIC PROPERTIES OF NEURONS IN MACAQUE AREA V2

We recorded from single cells in area V2 of cynomolgus monkeys using s tandard acute recording techniques. After measuring each cell's spatia l and temporal properties, we performed several tests of its chromatic properties using sine-wave gratings modulated around a mean gray back ground. Most cells behaved Like neurons in area V1 and their responses were adequately described by a model that assumes a linear combinatio n of cone signals. Unlike in V1, we found a subpopulation of cells who se activity was increased or inhibited by stimuli within a narrow rang e of color combinations. No particular color directions were preferent ially represented. V2 cells showing color specificity, including cells showing narrow chromatic tuning, were present in any of the stripe co mpartments, as defined by cytochrome-oxidase (GO) staining. An additio n of chromatic contrast facilitated the responses of most neurons to g ratings with various luminance contrasts. Neurons in all three CO comp artments gave significant responses to isoluminant gratings. Receptive -field properties of cells were generally similar for luminance and ch romatically defined stimuli. We found only a small number of cells wit h a clearly identifiable double-opponent receptive-field organization.