Center-Surround Interaction in X and Y Cells In the Lateral Geniculate Nucleus of the Cat as a Function of Adaptation.

The strength of the surround mechanism in cells of the lateral geniculate nucleus of the cat was studied at three adaptation levels, high mesopic, low mesopic and completely dark adapted. Extracellular recordings were made from 72 cells on 25 unanesthetized cats. Cells were classified as X or Y. The results indicated that the strength of the surround mechanism of geniculate cells changes with adaptation level. The response of the surround mechanism was weakest following complete dark adaptation but it did not disappear completely as is usually found in dark adapted retinal cells. The change in strength of the surround mechanism of geniculate cells occurs only following conplete dark adaptation and is, therefore, probably not determined by the relative rod and cone inputs to a cell.