Early visual adaptation in color opponent goldfish ganglion cells.

The initial stages of light and dark adaptation in the human visual system cannot be explained by a simple relation between sensitivity and pigment bleaching. We found changes in sensitivity in the goldfish ganglion cells similar to those seen in humans, and our results from experiments suggest that a change in gain, rather than an overloading of the ganglion cell activity, is responsible for the sensitivity loss. Furthermore, long wavelength background lights selected to stimulate only the long wavelength receptor mechanism produce only the early sensitivity changes in the medium wavelength cone mechanism being monitored at the ganglion cell. This suggests that the early gain changes occur due to neural interaction where different receptor signals merge.