A comparison of the shift response of X- and Y-cells in the cat's retina.

The shift response (McIlwain or peripheral effect) was elicited by either flashing or shifting a grating while the receptive field (RF) was covered by a 30 degree mask in the cat. The responses elicited by shifting the grating was comparable to that elicited by flashing the grating. In 10% of the units, the on- and off-responses elicited by flashing the grating were unequal in amplitude. The larger response corresponded with the light phase which leads to excitation of the surround mechanism of the RF. The maximum firing rates of the shift response did not differ in the different types of units, but the amplitude of the shift response (maximum - maintained firing rates) was significantly larger in Y-cells. For all types of cells, the amplitude of the shift response increased with greater eccentricity of the RF. A strong inhibitory period was found in on-center Y-cells but not in the other types of cells. The latency of the shift response was significantly shorter in Y-cells. The differences in the responses of X- and Y-cells suggest that the lateral pathways used are different for the X- and Y-cells.