Dynamical mechanisms underlying contrast gain control in single neurons.

Recent neurophysiological experiments have revealed that the linear and nonlinear kernels of the transfer function in sensory neurons are not static. Rather, they are adaptive to the contrast or the variance of time-varying input stimuli, exhibiting a contrast gain control phenomenon. We investigated the underlying biophysical causes of this phenomenon by simulating and analyzing the leaky integrate-and-fire and the Hodgkin-Huxley neuronal models. Our findings indicate that contrast gain control may result from the synergistic cooperation of the nonlinear dynamics of spike generation and the statistical properties of the stimuli. The resulting statistics-dependent stimulus threshold is shown to be a key factor underlying the adaptation of frequency tuning and amplitude gain of a neuron's transfer function in different stimulus environments.