The effect of adaptation level on the responses of two types of on centre cells in the cat optic tract

Single cell recordings were made from on centre retinal ganglion cells in the cat. Three types of stimuli were used in the study: a 0.3 degree spot flashed in the centre of the cell's receptive field, an annulus flashed in the receptive field peripheral, or a centre spot and peripheral annulus presented together. The purpose of the study was to determine if response differences between Group I and Group II cells (transient and sustained cells) held at 3 adaptation levels. The response differences reported in earlier studies were found to exist at a high (1.23 log cd/m²) and medium (0.23 log cd/m²) background but not a low background (-1.76 log cd/m²). Speculations concerning the neurophysiological basis of the results are made; also the functional significance of these two types of cells is discussed. (Journal received 21 March, 1975).