Functional circuitry of visual adaptation in the retina
Functional circuitry of visual adaptation in the retina
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DOI：
10.1113/jphysiol.2008.156638
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发表时间：
2008-09-15
影响因子：
5.5
通讯作者：
Demb, Jonathan B.
中科院分区：
文献类型：
--
作者：
Demb, Jonathan B.
视觉系统不断调整其敏感度，或“适应”，以适应周围环境的条件。自适应在输入信号较弱时增加响应，以提高信噪比，在输入信号较强时减少响应，以防止响应饱和。视网膜神经节细胞主要适应光输入的两个特性：平均强度和强度随时间的变化（对比度）。本文综述了哺乳动物视网膜对比度适应的细胞机制。神经节细胞感受野中心的高对比度降低了尖峰响应的增益。增益控制的机制部分出现在突触前双极细胞的输入，部分在锋电位产生的过程中。强对比刺激后，神经节细胞表现出延长的后超极化，主要由抑制突触前双极细胞的谷氨酸释放驱动。神经节细胞也适应其外周感受野的高对比度。长突细胞携带的长距离适应性信号直接抑制神经节细胞，引起超极化，并抑制突触前双极末梢，减少其突触输出的增益。因此，神经节细胞中的对比度适应涉及增益控制和超极化的多种突触和内在机制。神经节细胞中的几种适应形式起源于突触前双极细胞。
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.