Kelly D H, Wilson H R
Science. 1978 Nov 24;202(4370):896-9. doi: 10.1126/science.715449.
A well-known solution of the diffusion equation gives an exponential square-root function as the frequency response for a one-dimensional diffusion or transmission process. When two or more such processes are cascaded, the result is still an exponential square-root characteristic, but with a longer time constant. This seems to explain why flicker thresholds obey the Kelly-Veringa diffusion model at high frequencies, even though the psychophysically inferred diffusion process is much slower than the first stage of visual transduction measured by, for example, late receptor potentials. Two such stages in tandem are sufficient to account for the psychophysical data, because the psychophysical time constant is proportional to the square of the number of stages involved. In addition, the nonlinear behavior of flicker thresholds under intense light adaptation can be explained if the loss factor in the first stage is proportional to the amount of the photopigment bleached. Apparently the flicker thresholds are governed by first- and second-order retinal neurons.
扩散方程的一个著名解给出了指数平方根函数，作为一维扩散或传输过程的频率响应。当两个或更多这样的过程级联时，结果仍然是指数平方根特性，但时间常数更长。这似乎解释了为什么闪烁阈值在高频时服从凯利 - 韦林加扩散模型，尽管从心理物理学推断的扩散过程比例如晚期受体电位测量的视觉转导第一阶段要慢得多。两个这样串联的阶段足以解释心理物理学数据，因为心理物理学时间常数与所涉及阶段数的平方成正比。此外，如果第一阶段的损失因子与漂白的光色素量成正比，那么强光适应下闪烁阈值的非线性行为就可以得到解释。显然，闪烁阈值受视网膜一级和二级神经元的控制。
