Comparison of signal and adaptive sensitivity profiles of the surround mechanism of cat retinal ganglion cells.

Signal and adaptive sensitivity profiles of the surrounds of cat retinal ganglion cells were determined by varying the position of concentric annuli whose outside and inside diameters varied but whose total area remained constant. Signal sensitivity profiles were determined by adjusting the luminances of these annuli so as to produce a weak suprathreshold response of constant magnitude and time course. Adaptive sensitivity profiles were determined by varying the luminances of concentric equal-area, unmodulated annuli until the response to a temporally modulated annulus attained a criterion level. The results provided evidence that the retinal region over which the surround mechanism of an X cell pools adaptive information and pools signals are the same, and that the distribution of adaptive and signal sensitivities within these regions is similar. A small number of X cells showed local adaptation effects. The adaptive pooling area appeared to be smaller than the signal pooling area for Y cells.