Luminance adaptation

The rate of photons arriving at the retina varies over a billion-fold between a moonlit night and a sunny day, yet we can use vision in both conditions. The ability to adjust visual circuits to cover this enormous range of light intensities is called luminance adaptation. This chapter describes the theoretical and biological constraints on luminance adaptation and the many neural mechanisms that implement this computation at different locations in the retina. While the circuit locations differ, these mechanisms share an ability to work quickly, enabling rapid adjustments at each saccade. The last section of the chapter explores luminance adaptation at longer timescales-minutes and hours-where a host of different mechanisms come into play, from neuromodulators to receptor composition at synapses to protein localization.