Role of sustained neurones of cat lateral geniculate nucleus in processing luminance information.

The properties of the sustained cells in the lateral geniculate nucleus of cat have been studied quantitatively. These cells may be subdivided into two groups, the brightness and the darkness detectors. The former is photoexcitatory neurone and the latter, photoinhibitory. In both types, the rates of sustained discharges are closely related to the levels of retinal illumination over a range about 4 log units. The receptive fields of sustained cells again can be roughly divided into two subtypes according to their size. The large receptive field cells all belong to darkness detectors and are distributed mostly at retinal periphery, which may play some role in signalling the background luminance. The small receptive field cells comprise all brightness detectors and a part of darkness detectors, which are located predominantly around area centralis and may transmit the message of brightness or darkness about picture details and enhance the boundaries of a two-dimensional figure.