REDISTRIBUTION OF SYNAPTIC EFFICACY BETWEEN NEOCORTICAL PYRAMIDAL NEURONS

EXPERIENCE-dependent potentiation and depression of synaptic strength has been proposed to subserve learning and memory by changing the gain of signals conveyed between neurons(1,2). Here we examine synaptic pl asticity between individual neocortical layer-5 pyramidal neurons, We show that an increase in the synaptic response, induced by pairing act ion-potential activity in pre- and postsynaptic neurons, was only obse rved when synaptic input occurred at low frequencies. This frequency-d ependent increase in synaptic responses arises because of a redistribu tion of the available synaptic efficacy and not because of an increase in the efficacy. Redistribution of synaptic efficacy could represent a mechanism to change the content, rather than the gain, of signals co nveyed between neurons.