Contrast Adaptation in Simple Cells by Changing the Transmitter Release Probability

Using a recurrent neural network of excitatory spiking neurons with adapting synapses we show that both effects could be explained by a fast and a slow compo(cid:173) nent in the synaptic adaptation. This component-given by infomax learning rule-explains contrast adaptation of the averaged membrane potential (DC component) as well as the surprising experi(cid:173) mental result, that the stimulus modulated component (Fl component) of a cortical cell's membrane potential adapts only weakly. Based on our results, we propose a new experiment to estimate the strength of the ef(cid:173) fective excitatory feedback to a cortical neuron, and we also suggest a relatively simple experimental test to justify our hypothesized synaptic mechanism for contrast adaptation.