We propose a novel discrete model of central pattern generators (CPG), neuronal ensembles
generating rhythmic activity. The model emphasizes the role of nonsynaptic interactions
and the diversity of electrical properties in nervous systems. Neurons in the model
release different neurotransmitters into the shared extracellular space (ECS) so each
neuron with the appropriate set of receptors can receive signals from other neurons.
We consider neurons, differing in their electrical activity, represented as finite-state
machines functioning in discrete time steps. Discrete modeling is aimed to provide
a computationally tractable and compact explanation of rhythmic pattern generation
in nervous systems. The important feature of the model is the introduced mechanism
of neuronal competition which is shown to be responsible for the generation of proper
rhythms. The model is illustrated with an example of the well-studied feeding network
of a pond snail. Future research will focus on the neuromodulatory effects ubiquitous
in CPG networks and the whole nervous systems.
