Sparse and dense encoding in layered associative network of spiking neurons

摘要

A synfire chain is a simple neural network model which can transmit stable synchronous spikes called a pulse packet. However how synfire chains coexist in one network remains to be elucidated. We have studied the activity of a layered associative network of leaky integrate-and-fire neurons which connections are embedded with memory patterns by the Hebbian learning rule. We analyze their activity by the Fokker-Planck method. In our previous report, when a half of neurons belongs to each memory pattern (pattern rate F = 0.5), the temporal profiles of the network activity is split into temporally clustered groups called sublattices under certain input conditions. In this study, we show that when the network is sparsely connected (F < 0.5), synchronous firings of the memory pattern are promoted. On the contrary, the densely connected network (F > 0.5) inhibit synchronous firings. The basin of attraction and the storage capacity of the embedded memory patterns also depend on the sparseness of the network. We show that the sparsely (densely) connected networks enlarge (shrink) the basion of attraction and increase (decrease) the storage capacity.