Browse all publications by topic
Browse all publications by year
- P. Adorjan and
K. Obermayer. Contrast adaptation in simple cells by changing the
transmitter release probability.
.
In Advances in Neural Information Processing Systems 11, pages
76-82, Cambridge, Massachusetts, 1999. MIT Press.
(FTP Gzipped PostScript, 7 pages, 37 kb)
The contrast response function (CRF) of many neurons in the primary
visual cortex saturates and shifts towards higher contrast values following
prolonged presentation of high contrast visual stimuli. 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 component in the
synaptic adaptation. (i) Fast synaptic depression leads to saturation of the
CRF and phase advance in the cortical response to high contrast stimuli. (ii)
Slow adaptation of the synaptic transmitter release probability is derived
such that the mutual information between the input and the output of a
cortical neuron is maximal. This component - given by infomax learning rule -
explains contrast adaptation of the averaged membrane potential (DC
component) as well as the surprising experimental result, that the stimulus
modulated component (F1 component) of a cortical cells membrane potential
adapts only weakly. Based on our results, we propose a new experiment to
estimate the strength of the effective excitatory feedback to a cortical
neuron, and we also suggest a relatively simple experimental test to justify
our hypothesized synaptic mechanism for contrast adaptation.
|
