Modeling rhythmic patterns in the hippocampus

TL;DR

This paper models hippocampal neuronal network dynamics using FitzHugh-Nagumo neurons, revealing various rhythmic patterns, the impact of synaptic asymmetry, and multistability with hysteresis effects.

Contribution

It introduces a detailed neuronal circuit model capturing multiple hippocampal rhythms and analyzes how synaptic asymmetry influences network synchronization and multistability.

Findings

Identified gamma, theta, and theta/gamma rhythms in the model.

Demonstrated that synaptic asymmetry reduces dynamical diversity.

Showed multistability and hysteresis in network behavior.

Abstract

We investigate different dynamical regimes of neuronal network in the CA3 area of the hippocampus. The proposed neuronal circuit includes two fast- and two slowly-spiking cells which are interconnected by means of dynamical synapses. On the individual level, each neuron is modeled by FitzHugh-Nagumo equations. Three basic rhythmic patterns are observed: gamma-rhythm in which the fast neurons are uniformly spiking, theta-rhythm in which the individual spikes are separated by quiet epochs, and theta/gamma rhythm with repeated patches of spikes. We analyze the influence of asymmetry of synaptic strengths on the synchronization in the network and demonstrate that strong asymmetry reduces the variety of available dynamical states. The model network exhibits multistability; this results in occurrence of hysteresis in dependence on the conductances of individual connections. We show that switching between different rhythmic patterns in the network depends on the degree of synchronization between the slow cells.