A synaptic mechanism for retinal adaptation to luminance and contrast.
A synaptic mechanism for retinal adaptation to luminance and contrast.
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DOI：
10.1523/jneurosci.2631-11.2011
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发表时间：
2011-07-27
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影响因子：
--
通讯作者：
Singer JH
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文献类型：
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作者：
Jarsky T;Cembrowski M;Logan SM;Kath WL;Riecke H;Demb JB;Singer JH
初级感觉回路中的信号增益通过适应过程与刺激强度相匹配。视网膜神经回路适应视觉场景统计，包括光刺激的均值(背景适应)和时间变化(对比度适应)。视网膜双极细胞和突触的固有特性有助于背景和对比度适应，但目前尚不清楚这两种形式的适应是否依赖于相同的细胞机制。对双极细胞突触的研究发现了突触的增益控制机制，但这些机制与视觉处理的相关性尚不确定，因为历史上人们关注的是快速的相性传递，而不是环境光引起的紧张性传递。在这里，我们研究了在生理范围内，由微小的、持续的膜电位(Vm)调制所引起的双极细胞突触传递的依赖于使用的调节。在小鼠视网膜切片制备中，我们从视杆双极(RB)和AII无长突细胞中进行了成对的全细胞记录。准白噪声电压指令调制的Rb Vm和诱发的AII中的EPSC。我们分别通过去极化Vm或增加其方差来模拟背景亮度或对比度的变化。对突触传递的线性系统分析表明，增加突触前Vm的均值或方差都会降低增益。进一步的电生理和计算分析表明，对平均电位的适应是钙通道失活和小泡耗竭共同作用的结果，而对变异的适应只是小泡耗尽的结果。因此，背景和对比度适应显然部分依赖于共同的突触机制。
The gain of signaling in primary sensory circuits is matched to the stimulus intensity by the process of adaptation. Retinal neural circuits adapt to visual scene statistics, including the mean (background adaptation) and the temporal variance (contrast adaptation) of the light stimulus. The intrinsic properties of retinal bipolar cells and synapses contribute to background and contrast adaptation, but it is unclear whether both forms of adaptation depend on the same cellular mechanisms. Studies of bipolar cell synapses identified synaptic mechanisms of gain control, but the relevance of these mechanisms to visual processing is uncertain owing to the historical focus on fast, phasic transmission rather than the tonic transmission evoked by ambient light. Here, we studied use-dependent regulation of bipolar cell synaptic transmission evoked by small, ongoing modulations of membrane potential (VM) in the physiological range. We made paired whole-cell recordings from rod bipolar (RB) and AII amacrine cells in a mouse retinal slice preparation. Quasi-white noise voltage commands modulated RB VM and evoked EPSCs in the AII. We mimicked changes in background luminance or contrast, respectively, by depolarizing the VM or increasing its variance. A linear systems analysis of synaptic transmission showed that increasing either the mean or the variance of the presynaptic VM reduced gain. Further electrophysiological and computational analyses demonstrated that adaptation to mean potential resulted from both Ca channel inactivation and vesicle depletion, whereas adaptation to variance resulted from vesicle depletion alone. Thus, background and contrast adaptation apparently depend in part on a common synaptic mechanism.