Synchrony of fast-spiking interneurons interconnected by GABAergic and electrical synapses

We investigate the combined effects of electrical synapses (gap junctions) and GABAergic synapses on the synchronization of neuronal firing in a network of fast-spiking (FS) interneurons. We analytically study a system consisting of two identical FS neurons coupled by both gap junctions and GABAergic synapses in two cases, one in which the GABAergic connections are bi-directional (and identical) and one in which they are uni-directional (with identical, bi-directional gap junctions in both cases). Applying the phase reduction method to such a network, we find that if the two neurons are coupled by only electrical synapses, then they exhibit stable synchrony, whereas, if they are also coupled by chemical synapses, then they exhibit a variety of states with different relative spike timings, including synchronous, anti-synchronous and non-phase-locked states. Such coherence between the elements of an FS neuron pair depends on the synaptic organization and can be changed by altering the stimulus intensity and the conductance ratio between chemical and electrical synapses. Finally, we report the results of numerical simulations conducted to investigate the collective properties of a large-scale network of FS interneurons.