Figure 7.

H1 cell receptive field in the presence of HEPES. A, Horizontal cell response as a function of spot diameter in the absence (solid line) and presence (dashed line) of HEPES. Stimuli were spots sinusoidally modulated at 2 Hz. Response amplitude was measured as the strength of the Fourier component of the membrane voltage at the stimulus frequency, normalized to the maximum amplitude. HEPES causes responses to plateau at larger spot sizes, indicating larger receptive field size (n = 9). CTR, Control. B, Horizontal cell response as a function of annulus inner diameter (outer diameter was fixed at 2000 μm) in the absence (solid line) and presence (dashed line) of 20 mm HEPES. Stimuli and measurement parameters were the same as in A. Responses are stronger at larger annulus inner diameters in the presence of HEPES, indicating larger receptive field size (n = 9).