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Robert Shapley; The contrast gain control from 1978 till now. Journal of Vision 2013;13(15):T21. doi: 10.1167/13.15.21.
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My talk is about the paper that introduced the idea of a contrast gain control in the retina:
Shapley R and Victor JD. The effect of contrast on the transfer properties of cat retinal ganglion cells. J Physiol. 1978; 285: 275–298.
In the late 1970s, to study properties of cat X and Y retinal ganglion cells, Jonathan Victor and I used the sum-of-sinusoids method that Bruce Knight and Jonathan had invented. We measured first- and second-order kernels as functions of temporal frequency, and pairs of temporal frequencies, respectively. We discovered an unexpected nonlinearity in the retina. First-order kernels in both X and Y cells did not scale with stimulus contrast. At higher contrast there was a systematic phase advance at higher temporal frequencies, and a lower than expected growth in amplitude at lower temporal frequencies. The effect of contrast did not depend on response amplitude of the ganglion cell but on the space-averaged stimulus contrast. The contrast effect was caused by feedback from late in retinal processing to an early stage before the nonlinearity that generated second-order responses. The nonlinear feedback mechanism was a contrast gain control that adjusted retinal dynamic transfer properties as a function of stimulus contrast. The concept of a contrast gain control later was applied to the visual cortex where it was called “normalization.” The contrast gain control also has been useful in understanding visual perception as well as neural response properties.
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