REGULATION OF SYNAPTIC EFFICACY BY COINCIDENCE OF POSTSYNAPTIC APS AND EPSPS

Activity-driven modifications in synaptic connections between neurons in the neocortex may occur during development and learning. In dual wh ole-cell voltage recordings from pyramidal neurons, the coincidence of postsynaptic action potentials (APs) and unitary excitatory postsynap tic potentials (EPSPs) was found to induce changes in EPSPs. Their ave rage amplitudes were differentially up- or down-regulated, depending o n the precise timing of postsynaptic APs relative to EPSPs. These obse rvations suggest that APs propagating back into dendrites serve to mod ify single active synaptic connections, depending on the pattern of el ectrical activity in the pre- and postsynaptic neurons.