Aging of human short-wave cone pathways
Aging of human short-wave cone pathways
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DOI：
10.1073/pnas.1119770109
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发表时间：
2012-08-14
影响因子：
11.1
通讯作者：
Werner, John S.
中科院分区：
文献类型：
--
作者：
Shinomori, Keizo;Werner, John S.
视网膜图像通过三条生理和解剖上不同的路径同时进行采样，并且在很大程度上是独立的，每条路径都有单独的开和关细分。视网膜回路引起接受短波敏感(S)视锥细胞输入的ON通路是众所周知的，但S视锥关闭回路更具争议性。在这里，我们通过测量产生增加或减少S视锥刺激的刺激的阈值来表征年轻和老年观察者假设的S视锥通路的时间特性，而对中波和长波敏感的视锥细胞是未调制的。我们根据脉冲响应函数来描述数据，脉冲响应函数是对无限短持续时间的闪光的理论响应，可以根据该函数预测对任何时间变化的刺激的响应。结果表明，S锥体对递增的反应比对递减的反应快，但这种差异在年龄较大的个体中明显更大。递增和递减响应的脉冲响应函数幅度在不同个体之间高度相关，而时间不相关。这有力地表明，幅度是由S锥体开和关反应(光感受器)共同的神经回路控制的，而时序则由不同的受体后通路控制。可能的Off通路反应较慢归因于不同的视网膜回路，可能归因于On通路中不存在符号倒置的无长突细胞。值得注意的是，这一途径在老年人中受到选择性地影响，使其变慢，而S锥体反应的时间特性在人的一生中是稳定的。
The retinal image is sampled concurrently, and largely independently, by three physiologically and anatomically distinct pathways, each with separate ON and OFF subdivisions. The retinal circuitry giving rise to an ON pathway receiving input from the short-wave-sensitive (S) cones is well understood, but the S-cone OFF circuitry is more controversial. Here, we characterize the temporal properties of putative S-cone ON and OFF pathways in younger and older observers by measuring thresholds for stimuli that produce increases or decreases in S-cone stimulation, while the middle-and long-wave-sensitive cones are unmodulated. We characterize the data in terms of an impulse response function, the theoretical response to a flash of infinitely short duration, from which the response to any temporally varying stimulus may be predicted. Results show that the S-cone response to increments is faster than to decrements, but this difference is significantly greater for older individuals. The impulse response function amplitudes for increment and decrement responses are highly correlated across individuals, whereas the timing is not. This strongly suggests that the amplitude is controlled by neural circuitry that is common to S-cone ON and OFF responses (photoreceptors), whereas the timing is controlled by separate postreceptoral pathways. The slower response of the putative OFF pathway is ascribed to different retinal circuitry, possibly attributable to a sign-inverting amacrine cell not present in the ON pathway. It is significant that this pathway is affected selectively in the elderly by becoming slower, whereas the temporal properties of the S-cone ON response are stable across the life span of an individual.