Detection sensitivity and temporal resolution of visual signals near absolute threshold in the salamander retina
Detection sensitivity and temporal resolution of visual signals near absolute threshold in the salamander retina
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DOI：
10.1523/jneurosci.2339-04.2005
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发表时间：
2005-01-12
影响因子：
5.3
通讯作者：
Rieke, F
中科院分区：
文献类型：
--
作者：
Chichilnisky, EJ;Rieke, F
几项研究表明，视觉系统可以检测微弱的光线，其保真度仅受光子吸收的泊松波动和视紫红质的自发激活的限制。如果正确，这意味着视杆光感受器产生的反应的神经处理是高效且无噪音的。然而，实验的不确定性使得这个结论站不住脚。此外，之前的工作没有提供有关如何准确地表示刺激时间的信息。在这里，通过使用记录的响应来识别闪光时间，在几乎匹配的实验条件下比较蝾螈杆和视网膜神经节细胞（RGC）的检测灵敏度和时间分辨率。在检测阈值处，RGC 可以可靠地发出 20-50 个光子吸收的信号，但 RGC 感受野内的视杆发出的刺激信号要弱 3-10 倍。对于比检测阈值高 10 倍的闪光强度，一些 RGC 可以以优于 100 毫秒的分辨率（在杆极限的 2 倍之内）区分刺激时间。 RGC 和视杆细胞灵敏度之间的关系不能用视网膜电路中增加的噪声来解释，但可以用视杆细胞信号汇集后作用的阈值来解释。杆状信号的模拟表明，限制时间分辨率的是连续噪声，而不是视紫红质的自发激活或单光子响应的波动。因此，弱光的检测受到视网膜处理的限制，但在较高的光水平下，突触传递、突触输入的细胞整合以及 RGC 中的尖峰生成忠实地传达了有关光子吸收时间的信息。
Several studies have suggested that the visual system can detect dim lights with a fidelity limited only by Poisson fluctuations in photon absorption and spontaneous activation of rhodopsin. If correct, this implies that neural processing of responses produced by rod photoreceptors is efficient and effectively noiseless. However, experimental uncertainty makes this conclusion tenuous. Furthermore, previous work provided no information about how accurately stimulus timing is represented. Here, the detection sensitivity and temporal resolution of salamander rods and retinal ganglion cells (RGCs) are compared in nearly matched experimental conditions by using recorded responses to identify the time of a flash. At detection threshold, RGCs could reliably signal the absorption of 20-50 photons, but the rods within the RGC receptive field could signal stimuli 3-10 times weaker. For flash strengths 10 times higher than detection threshold, some RGCs could distinguish stimulus timing with a resolution finer than 100 msec, within a factor of 2 of the rod limit. The relationship between RGC and rod sensitivity could not be explained by added noise in the retinal circuitry but could be explained by a threshold acting after pooling of rod signals. Simulations of rod signals indicated that continuous noise, rather than spontaneous activation of rhodopsin or fluctuations in the single-photon response, limited temporal resolution. Thus, detection of dim lights was limited by retinal processing, but, at higher light levels, synaptic transmission, cellular integration of synaptic inputs, and spike generation in RGCs faithfully conveyed information about the time of photon absorption.