Adaptation in catfish retina.
1. We define absolute sensitivity as (voltage/illuminance) and incremental sensitivity as the peak-to-peak amplitude of the first-order (Wiener) kernels. 2. Incremental sensitivity of the horizontal cells is the local slopes of the Michaelis-Menten equation and that of more proximal neurons is the Fechner slope. In a log-log plot, the former has a slope of -2, whereas the latter a slope of -1, as predicted by Williams and Gale (39). 3. During a moderate to strong steady illumination, absolute sensitivity decreases but incremental sensitivity increases. The reverse occurs during dark adaptation. 4. The presence of a steady illumination did not prevent signal transmission from horizontal to ganglion cells. 5. From these results we conclude that: adaptation in the catfish retina includes two components: a) a lateral shift of the voltage-intensity curve along the intensity axis, and b) changes in the time course of light-evoked response. We argue that the latter phenomenon is related to the presumed horizontal cell-to-receptor cell negative feedback.
D000222:Adaptation, Physiological; D000818:Animals; D003623:Dark Adaptation; D004594:Electrophysiology; D005399:Fishes / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D012160:Retina / Q000166:cytology / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*