We explore a synaptic plasticity model where potentiation and depression ar
e induced by precisely timed pairs of synaptic events and postsynaptic spik
es. We include the observation that strong synapses undergo relatively less
potentiation than weak synapses, whereas depression is independent of syna
ptic strength. After random stimulation the synaptic weights reach a stable
equilibrium distribution. Competition can be introduced separately by a me
chanism that scales synaptic strengths as a function of postsynaptic activi
ty. The plasticity rules select inputs which have a strong correlation with
other inputs. (C) 2001 Published by Elsevier Science B.V.