RESPONSES TO COLOR OF NEURONS IN AREA 7A OF THE INFERIOR PARIETAL LOBULE OF THE RHESUS-MONKEY

A single-unit study on area 7a of alert, fixating rhesus monkeys revea led responsiveness to primary colours comparable to white light respon siveness shown in other cells. Mostly decremented, some biphasic, and a small portion with incremented neuronal firing response were observe d, following stimulation of cells by parafoveal receptive field, recta ngular, approximately 20 degrees x 20 degrees red, green or blue-viole t light stimuli. The same cell showed no response to white light. Rece ptive fields of these colour-sensitive cells, like those of white-sens itive cells, were mostly contralateral, some ipsilateral and a few in both hemifields. Augmentation of responses following preconditioning e lectrical stimulation of lateroposterior-pulvinar targets was observed as with the white-light sensitive cells. It is noteworthy that this m onkey area 7a colour sensitivity is complementary to previously demons trated white light sensitivity. The specific properties revealed by th ese cells suggest separate channels within area 7a for colour and for achromatic light, the colour sensitivity possibly relevant when chroma ticity is of generalized import, and these may subserve the animal's o rienting response to colour appearance in the near-periphery visual fi eld.