The contributions of ON- and OFF-pathways to contrast sensitivity and spatial resolution in goldfish

DL-2-amino-4-phosphonobutyric acid (APB) reduces the sensitivity of ON- and OFF-responses in goldfish retina, although the ON-responses are reduced significantly more than the OFF-responses. This paper describes the effects of APB on behavioral sensitivity of goldfish to spatial sinusoidal gratings. Fish were classically conditioned to suppress respiration upon presentation of gratings drifting at 1 Hz; contrast thresholds were measured by an observer-based two-alternative forced-choice procedure. Thresholds were repeated following intraocular injections of APB or physiological saline. Saline had no effect, but APB dramatically reduced contrast sensitivity and shifted contrast sensitivity functions to lower spatial frequencies. The results suggest that both ON- and OFF-pathways are necessary for normal spatial vision and that the effects of APB are consistent with the disruption of both ON- and OFF-pathways.