The response of cat horizontal cells to flicker stimuli of different area, intensity and frequency

In the cat's retina we analyzed the sinewave light flicker response nonlinearity of Hm-type horizontal cells. (For a description of the three types of dynamic responses of cat retinal H-units see Foerster et al., 1977). For equal decreases in the Hm-response amplitude an increase in stimulus frequency had a much stronger linearizing effect than a decrease in stimulus area. Thus the distortion is not simply proportional to response amplitude. Both Hm- and Hn-units had frequency dependent nonlinear area-response functions. The receptive field of Hm-units increased dramatically with stimulus frequency, e.g. from 1 degrees at 1 Hz to 8 degrees or more at 44 Hz. Intensity transfer data could be described by the function Lb-(sigmab + Lb)-1 with b approximately 1 for Hm-units and b approximately 0.5 for Hn-units. Distortion values predicted from intensity transfer data were too high. It was also found that higher harmonics were attenuated more than the first harmonic at increasing frequencies. Therefore it appeared that some filtering preceded the amplitude compression stage.