Action Potential Bursts Modulate the NMDA-R Mediated Spike Timing Dependent Plasticity in a Biophysical Model

Abstract

Spike timing dependent plasticity (STDP) requires the temporal association of presynaptic and postsynaptic action potentials (APs). However, some synapses in the CA1 region of the hippocampus are suprisingle unreliable at signaling the arrival of single spikes to the postsynaptic neuron [4]. In such unreliable synapses pairing of excitatory postsynaptic potentials (EPSPs) and single APs at low frequencies is ineffective at generating plasticity [2], [3]. A recent computational study [7] has shown that the shape of the STDP curve strongly depends on the burst interspike interval in the presence/absence of inhibition when a presynaptic dendritic burst and a postsynaptic somatic spike were paired together. In this study, we investigate via computer simulations the conditions under which STDP is affected when now a high frequency somatic burst instead of a single spike is paired with another dendritic spike. We show that during such pairing conditions in the absence of inhibition a symmetric STDP profile with a distinct positive LTP region is evident at 10-30ms interstimulus interval and flat LTD tails at all other interstimulus intervals. The symmetry is preserved at all burst interspike intervals. When inhibition is present, the STDP profile shape into a Mexican hat shaped one or an inverted symmetrical one with flat LTP tails.