EXTENSIVE DISINHIBITORY REGION BEYOND THE CLASSICAL RECEPTIVE-FIELD OF CAT RETINAL GANGLION-CELLS

Forty-three single fibres were recorded from cat optic tract. They were tested with flashing lines of different lengths and/or spots of different dimensions. The area of centre excitation and of surround inhibition were represented in the length (or dimension)-reponse functions by the -steep rising and falling phases, respectively. For most of the cells, a secondary gentle rise was seen when the stimulus extended beyond the inhibitory surround, indicating an extensive disinhibitory region (DIR) outside the classical receptive field (RF). Disinhibition appeared and developed concurrently with surround inhibition at stimulus intensities between 3 and 30 cd/m2, being represented in the phasic or the tonic component of responses depending on the cell type recorded.