Sensory coding in the vertebrate retina: towards an adaptive control of visual sensitivity

We propose a theoretical framework for the adaptive control of visual sensitivity in the vertebrate retina. The photoreceptor transfer function is modelled with a Michaelis-Menten law instead of a logarithmic function. This more plausible function has a biophysical correlate, and it allows consideration of the photoreceptor as the main locus of retinal adaptation. The retinal model suggests that the function of photoreceptors might be to control visual sensitivity, defined as the optimal transcoding of non-stationary visual information. This is done by using an adaptive transfer function whose parameters are spatiotemporally and locally estimated by the subsequent retinal circuit and fed back to the photoreceptors. The proposed model also supports the functional architecture of the vertebrate retina.