Crevier D W, Meister M
Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
J Neurophysiol. 1998 Apr;79(4):1869-78. doi: 10.1152/jn.1998.79.4.1869.
Periodic flashes of light have long served to probe the temporal properties of the visual system. Here we show that during rapid flicker of high contrast and intensity the eye reports to the brain only every other flash of light. In this regime, retinal ganglion cells of the salamander fire spikes on alternating flashes. Neurons across the entire retina are locked to the same flashes. The effect depends sharply on contrast and flash frequency. It results from a period-doubling bifurcation in retinal processing, and a simple model of nonlinear feedback reproduces the phenomenon. Pharmacological studies indicate that the critical feedback interactions require only cone photoreceptors and bipolar cells. Analogous period-doubling is observed in the human visual system. Under bright full-field flicker, the electroretinogram (ERG) shows a regime of period-doubling between 30 and 70 Hz. In visual evoked potentials from the occiput, the subharmonic component is even stronger. By analyzing the accompanying perceptual effects, we find that retinal period-doubling begins in the periphery of the visual field, and that it is the cause of a long mysterious illusory flicker pattern.
周期性的闪光长期以来一直用于探究视觉系统的时间特性。我们在此表明，在高对比度和高强度的快速闪烁期间，眼睛向大脑报告的仅是每隔一次的闪光。在此状态下，蝾螈的视网膜神经节细胞在交替的闪光时产生尖峰信号。整个视网膜的神经元都锁定在相同的闪光上。这种效应强烈依赖于对比度和闪光频率。它源于视网膜处理过程中的倍周期分岔，一个简单的非线性反馈模型再现了这一现象。药理学研究表明，关键的反馈相互作用仅需要视锥光感受器和双极细胞。在人类视觉系统中也观察到了类似的倍周期现象。在明亮的全场闪烁下，视网膜电图（ERG）显示在30至70赫兹之间存在倍周期状态。在枕部的视觉诱发电位中，次谐波成分甚至更强。通过分析伴随的感知效应，我们发现视网膜倍周期始于视野的周边，并且它是一种长期以来神秘的虚幻闪烁模式的成因。
