CAT LOCAL ELECTRORETINOGRAM TO INCREMENTAL STIMULI

Small retinal potentials generated in response to large area incremental stimuli were studied with averaging techniques. Below a retinal illumination of about 10-5 scotopic lm/mm2, the responses recorded between an electrode deep in the retina and an intravitreal electrode (local electroretinogram - LERG) to small (≤40%) incremental changes in light intensity appear to be linearly related to the incremental stimuli. The linear response consists of two components: the late receptor potential and the d.c. component. A pigment epithelium response was found to be normally absent from LERGs produced by large stimulus spots. This is consistent with an analysis of potentials generated within the eye. Above a retinal illumination of about 10-5 scotopic lm/mm2 the linear response is abolished and a new component, termed the vitreal non-linear component, appears. We interpret the disappearance of the linear response as a saturation of the rod mechanism. © 1969.