Learning direction selectivity through spike-timing dependent modificationof neurotransmitter release probability

It has recently been proposed that the direction selectivity of simple cell s emerges from an interplay of depressing and non-depressing synapses proje cting in an asymmetric arrangement onto these cells. We show that such an a symmetric arrangement may develop from a temporally asymmetric spike-based learning rule. The rule redistributes the probability of vesicle discharge, producing synapses with high discharge probability and strong depression i n one-half of the receptive field and low discharge probability and weak de pression in the other. This spatial shift together with the temporal phase advance of the depressing synapses adds up with the response of the surroun ding non-depressing synapses only when the stimulus moves in the preferred direction. (C) 2001 Elsevier Science B.V. All rights reserved.