Long and short-term synaptic plasticity and the formation of working memory: A case study

We study the collective behaviour of recurrent networks of integrate-and-fire neurons, connected by synapses whose efficacies are subjected to a spike-driven, and rate sensitive, Hebbian LTP and a homosynaptic depression, as well as a short-term, frequency dependent depression (STD). Through a mean field analysis, and numerical simulations of the coupled neural and synaptic dynamics, we show how repeated stimulations of the network can dynamically produce a synaptic structure supporting persistent, collective, stimulus-selective activity, that have been proposed since long as a substrate for 'working memory'. We discuss constraints relevant to the stability of the 'learning' process, and the related role of long-term synaptic depression as well as the effects of inclusion of STD. (C) 2001 Elsevier Science B.V. All rights reserved.