Distance- and Direction-Dependent Synaptic Weight Distributions for Directional Spike Propagation in a Recurrent Network: Self-actuated Shutdown of Synaptic Plasticity

Abstract

It has been suggested that directional spike propagation in a paradoxical way is organized in a recurrent network with anisotropic inhibition when excitatory connections to excitatory neurons (E–E) and inhibitory interneurons (E–I) are updated through spike-timing dependent plasticity. In this study, we show that both E–E and E–I connections have distance- and direction-dependent synaptic weight distributions in the recurrent network. E–E and E–I connections in the direction of spike propagation are more potentiated with increasing the distance between pre- and postsynaptic neurons. However, excitatory connections in the opposite direction of spike propagation are depressed regardless of the distance. In this network, the removal of the distance-dependency of E–I connections expands the width of directional spike propagation. On the other hand, the removal of the direction-dependency of E–I connections contracts spike propagation. These results show that the distance- and direction-dependent synaptic weight distributions contribute to directional spike propagation. The distance-dependent synaptic weight distribution, which suppresses activities in the lateral areas of the directional spike propagation, stops the progress of synaptic enhancement in those areas as if the synaptic plasticity is equipped with a self-actuated shutdown mechanism.