Potentiation Decay of Synapses and the Length Distributions of Synfire Chains Self-organized in Recurrent Neural Networks

摘要

Synfire chains are thought to underlie precisely-timed sequences of spikesobserved in various brain regions and across species. How they are formed isnot understood. Here we analyze self-organization of synfire chains through thespike-timing dependent plasticity (STDP) of the synapses, axon remodeling, andpotentiation decay of synaptic weights in networks of neurons driven by noisyexternal inputs and subject to dominant feedback inhibition. Potentiation decayis the gradual, activity-independent reduction of synaptic weights over time.We show that potentiation decay enables a dynamic and statistically stablenetwork connectivity when neurons spike spontaneously. Periodic stimulation ofa subset of neurons leads to formation of synfire chains through a randomrecruitment process, which terminates when the chain connects to itself andforms a loop. We demonstrate that chain length distributions depend on thepotentiation decay. Fast potentiation decay leads to long chains with widedistributions, while slow potentiation decay leads to short chains with narrowdistributions. We suggest that the potentiation decay, which corresponds to thedecay of early long-term potentiation of synapses (E-LTP), is an importantsynaptic plasticity rule in regulating formation of neural circuity throughSTDP.