Response of primate cones to sinusoidally flickering homochromatic stimuli.

1. The response of the primate cone photoreceptors to sinusoidally flickering stimuli has been obtained by monitoring the late receptor potential (LRP). 2. By comparing the response characteristics of the foveal local electroretinogram (LERG) before and after the intraocular infusion of sodium aspartate, it was found that the b-wave in the foveal LERG does not affect the monitoring of the LRP to steady-state flicker. 3. Functions describing the supra-threshold frequency response characteristics of the photoreceptors were obtained. 4. Linearity was found to hold for low amplitude responses, and temporal modulation transfer functions (MTFs) were obtained for the photoreceptors at various adaptation levels. 5. The cone photoreceptors were found to act approximately as passive low pass filters compounded with some low frequency attenuation. 6. The high frequency response of the photoreceptors at various adaptation levels tends toward a common high frequency asymptote, much like human psychophysical findings, and can be described by a diffusion model. 7. Non-linearities (convexity-upwards) suggest modest positive feedback at the level of the photoreceptors. 8. Mechanisms limiting the magnitude of the receptor response at low frequencies have little effect on the phase lag of the response.