VOLTAGE SIGNAL OF PHOTORECEPTORS AT VISUAL THRESHOLD
VOLTAGE SIGNAL OF PHOTORECEPTORS AT VISUAL THRESHOLD
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DOI：
10.1038/265181a0
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发表时间：
1977-01-01
期刊：
影响因子：
64.8
通讯作者：
MAXWELL, JH
中科院分区：
文献类型：
--
作者：
FAIN, GL;GRANDA, AM;MAXWELL, JH
人们早就知道，脊椎动物的光感受器可以发出吸收单个光量子的信号1。视觉系统的异常敏感性通常归因于光感受器的敏感性和高阶神经元对其信号的整合。如果能够记录视觉阈值时感受器的反应，就能对视觉敏感性作出更完整的解释。不幸的是，在绝对阈值下不可能做到这一点，主要是因为受体之间的相互作用2。在接近绝对阈值时，只有一小部分受体吸收量子，但来自这些细胞的光电流通过电子突触3传播到许多其他细胞。因此，受体中的电压响应是不均匀的，并且不可能知道哪些响应对阈值有贡献。幸运的是，这种困难不会出现在增量阈值，因为在明亮的背景光的存在下，从一个受体到下一个受体的响应变化是最小的。受体之间捕获量子数量的差异将远不如绝对阈值重要，受体之间的连接将趋于均衡它们的电压。在这份报告中，我们比较了光适应龟的行为反应的受体反应，并表明，在阈值的受体反应的幅度只有几微伏。
IT has long been known that vertebrate photoreceptors can signal the absorption of single quanta of light1. The extraordinary sensitivity of the visual system is usually ascribed both to the sensitivity of the photoreceptors and to the integration of their signals by higher-order neurones. A more complete explanation of visual sensitivity could be given if it were possible to record the response of receptors at the visual threshold. Unfortunately, it has not been possible to do this at the absolute threshold, largely because of interactions between receptors2. Near the absolute threshold only a small proportion of the receptors absorb quanta, but the photocurrent from these cells spreads through electronic synapses3to many other cells. Thus the voltage responses in the receptors are non-uniform, and it is not possible to tell which responses contribute to the threshold. Fortunately this difficulty does not arise at the increment threshold since in the presence of bright background light, the variation in response from one receptor to the next is minimal. The differences among the receptors in the number of quanta caught will be much less important than at absolute threshold, and the connections between the receptors will tend to equalise their voltages. In this report we compare receptor responses to behavioural responses in the light-adapted turtle and show that the receptor response at threshold is only a few microvolts in amplitude.