Synaptic depression mediates bistability in neuronal networks with recurrent inhibitory connectivity

When depressing synapses are embedded in a circuit composed of a pacemaker neuron and a neuron with no autorhythmic properties, the network can show t wo modes of oscillation. In one mode the synapses are mostly depressed, and the oscillations are dominated by the properties of the oscillating neuron . In the other mode, the synapses recover from depression, and the oscillat ions are primarily controlled by the synapses. We demonstrate the two modes of oscillation in a hybrid circuit consisting of a biological pacemaker an d a model neuron, reciprocally coupled via model depressing synapses. We sh ow that across a wide range of parameter values this network shows robust b istability of the oscillation mode and that it is possible to switch the ne twork from one mode to the other by injection of a brief current pulse in e ither neuron. The underlying mechanism for bistability may be present in ma ny types of circuits with reciprocal connections and synaptic depression.