Chen E P, Freeman A W
Biomedical Engineering Department, Northwestern University, Evanston, IL 60201.
Vision Res. 1989;29(3):271-91. doi: 10.1016/0042-6989(89)90076-x.
A linear model is described for the cat eye's signal-processing pathway, from the visual stimulus at the cornea, to cones, to X-type ganglion cells. The model contains elements representing the eye's optics, phototransduction, gain control, spatiotemporal processing by cell layers, and pure delay. Centre-surround antagonism in the model arises through the presence of a centre element producing a small spatial spread of signals, and an antagonistic element producing a larger spread. Two arrangements were tried, feedforward and feedback, in which the antagonistic element's output was subtracted from the centre element's output, and input, respectively. The model was fitted to empirical spatial and temporal frequency responses collected by Frishman et al. (1987), and accounted qualitatively for these data in the feedback, but not the feedforward, arrangement. The model's centre pathway comprises a cascade of low-pass spatial filters, as does the surround pathway. As a consequence, the spatial frequency responses for these two pathways closely approximate Gaussian functions of spatial frequency, and the spatial frequency response of the complete model at low temporal frequency closely matches that of the difference of Gaussians model.
本文描述了一种针对猫眼信号处理通路的线性模型，该通路从角膜处的视觉刺激开始，经过视锥细胞，再到X型神经节细胞。该模型包含代表眼睛光学、光转导、增益控制、细胞层的时空处理以及纯延迟的元素。模型中的中心-周边拮抗作用是通过一个产生小信号空间扩散的中心元素和一个产生大信号扩散的拮抗元素的存在而产生的。尝试了两种排列方式，即前馈和反馈，其中分别从前馈排列中从中心元素的输出中减去拮抗元素的输出，从反馈排列中从中心元素的输入中减去拮抗元素的输出。该模型与弗里什曼等人（1987年）收集的经验性空间和时间频率响应进行拟合，在反馈排列中对这些数据进行了定性解释，但在前馈排列中则不然。模型的中心通路包括一系列低通空间滤波器，周边通路也是如此。因此，这两条通路的空间频率响应非常近似于空间频率的高斯函数，并且完整模型在低时间频率下的空间频率响应与高斯差分模型的响应紧密匹配。
