Stability and Competition in Multi-spike Models of Spike-Timing Dependent Plasticity
Fig 1
A. Top-left: The STDP window with A+ < A−. Top-right: a triplet of spikes composed of two pre-post pairs with intervals Δt1 and Δt2. Bottom: the amount of synaptic modification in response to triplets, which is symmetric in the pair-based model. B. The average drift induced by the pair-based model on a population of excitatory synapses converging onto a single postsynaptic neuron, when A+ < A−. The black curve is a numerical evaluation of Eq 2 and the gray area is the simulation results. The half-width of the gray area is the standard error. The filled circle is the stable fixed point. The inset shows the w-dependent drift (Eq 3) C. The steady state distribution of synaptic weights obtained by simulation when A+ < A−. D. The steady state distribution of weights when half of the synapses receive correlated input (magenta) and the other half receive uncorrelated input (cyan). When A+ < A− correlated synapses are strengthened. E-H. The same as A-D, but for A+ > A−. Note that there is no stable fixed point in F, and that all the synapses are pushed to the upper bound in G and H. For these simulations, the constants of the STDP model were τ+ = τ− = 20 ms, A+ = 0.005 mV and A− = 1.0.1 A+ in A-D and A− = 0.005 mV and A+ = 1.0.1 A− in E-H.