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Functional circuitry of visual adaptation in the retina
Author(s) -
Demb Jonathan B.
Publication year - 2008
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2008.156638
Subject(s) - receptive field , neuroscience , retina , hyperpolarization (physics) , parasol cell , retinal waves , inhibitory postsynaptic potential , ganglion , biology , bistratified cell , giant retinal ganglion cells , automatic gain control , retinal ganglion cell , biophysics , chemistry , physics , amplifier , optoelectronics , organic chemistry , cmos , nuclear magnetic resonance spectroscopy
The visual system continually adjusts its sensitivity, or ‘adapts’, to the conditions of the immediate environment. Adaptation increases responses when input signals are weak, to improve the signal‐to‐noise ratio, and decreases responses when input signals are strong, to prevent response saturation. Retinal ganglion cells adapt primarily to two properties of light input: the mean intensity and the variance of intensity over time (contrast). This review focuses on cellular mechanisms for contrast adaptation in mammalian retina. High contrast over the ganglion cell's receptive field centre reduces the gain of spiking responses. The mechanism for gain control arises partly in presynaptic bipolar cell inputs and partly in the process of spike generation. Following strong contrast stimulation, ganglion cells exhibit a prolonged after‐hyperpolarization, driven primarily by suppression of glutamate release from presynaptic bipolar cells. Ganglion cells also adapt to high contrast over their peripheral receptive field. Long‐range adaptive signals are carried by amacrine cells that inhibit the ganglion cell directly, causing hyperpolarization, and inhibit presynaptic bipolar terminals, reducing gain of their synaptic output. Thus, contrast adaptation in ganglion cells involves multiple synaptic and intrinsic mechanisms for gain control and hyperpolarization. Several forms of adaptation in ganglion cells originate in presynaptic bipolar cells.