Receptive field mechanisms of cat X and Y retinal ganglion cells.

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Abstract
Receptive field properties of cat retinal ganglion cells with visual stimuli which were sinusoidal spatial gratings amplitude modulated in time by a sum of sinusoids were investigated. Neural responses were analyzed into the Fourier components at the input frequencies and the components at sum and difference frequencies. The 1st-order frequency response of X cells had a marked spatial phase and spatial frequency dependence which could be explained in terms of linear interactions between center and surround mechanisms in the receptive field. The 2nd-order frequency response of X cells was much smaller than the 1st-order frequency response at all spatial frequencies. The spatial phase and spatial frequency dependence of the 1st-order frequency response in Y cells in some ways resembled that of X cells. The Y 1st-order response declined to zero at a much lower spatial frequency than in X cells. The 2nd-order frequency response was larger in Y cells; the 2nd-order frequency components became the dominant part of the response for patterns of high spatial frequency. This implies that the receptive field center and surround mechanisms are physiologically quite different in Y cells from those in X cells and that the Y cells also receive excitatory drive from an additional nonlinear receptive field mechanism.