DO X AND Y RETINAL GANGLION CELLS SIGNAL CONTRAST? .

A major task for the peripheral parts of the visual system is to send to more central stations information about images whose luminance can vary over a vast range. In addition, this task must be performed within channels of rather limited capacity. It is reported that for the visual system of cats, at least, this problem seems to be solved by transmitting information about the contrast between parts of an image rather than about the absolute luminances of its parts. Results are presented that show that X and Y retinal ganglion cells respond systematically to contrast under a range of levels of retinal illumination but are relatively unresponsive to changes in luminance.