Tranchina D, Gordon J, Shapley R, Toyoda J
Proc Natl Acad Sci U S A. 1981 Oct;78(10):6540-2. doi: 10.1073/pnas.78.10.6540.
A basic question about visual perception is whether the retina produces a faithful or a distorted neural representation of the visual image. It is now well known that in some retinal pathways there are significant nonlinear transductions which distort the neural image. The next natural question is, What are the locations of the nonlinear stages within the retinal network? We report here on an investigation of linearity and nonlinearity of responses of horizontal cells in the turtle retina as an assay of the degree of nonlinearity in the outer plexiform layer of the retina. The visual stimuli were sinusoidal gratings; these patterns were modulated by contrast reversal with a sinusoidal time course. The conclusion from our experiments is that the turtle's horizontal cell responses show evidence only of linear spatial summation even at moderately high contrasts on moderately high background levels. Our work thus indicates that there is no significant distortion of the visual image by the photoreceptors or by the neural summation of photoreceptor signals by horizontal cells under normal physiological conditions. These results are consistent with the view that the major nonlinearities of the retina are proximal to the outer plexiform layer.
关于视觉感知的一个基本问题是，视网膜产生的是视觉图像的忠实神经表征还是扭曲的神经表征。现在众所周知，在一些视网膜通路中存在显著的非线性转导，这会扭曲神经图像。接下来自然的问题是，视网膜网络中非线性阶段的位置在哪里？我们在此报告一项关于龟视网膜水平细胞反应的线性和非线性的研究，以此作为视网膜外网状层非线性程度的一种检测方法。视觉刺激是正弦光栅；这些图案通过具有正弦时间进程的对比度反转进行调制。我们实验的结论是，即使在中等高背景水平下的中等高对比度情况下，龟的水平细胞反应也仅显示出线性空间总和的证据。因此，我们的工作表明，在正常生理条件下，光感受器或水平细胞对光感受器信号的神经总和不会对视觉图像造成显著扭曲。这些结果与视网膜的主要非线性位于外网状层近端的观点一致。
