Gait generation characterized by the phase sensitive properties of synaptically coupled neurons

Although central pattern generators (CPGs) are ubiquitous neural elements that generate the rhythmic movements of many biological systems, the mechanisms that govern controlled pattern generation is often poorly understood. In order to gain insights into the behavior of CPGs, we utilize phase sensitivity of the modeled Aplysia R15 neuron, which was incorporated into a small neuron ring circuit. R15 neurons are bursting neurons that are phase sensitive to current input, external or synaptic. Our simple model circuit consists of three or four unidirectionally connected neurons that have inhibitory synapses. By adjusting the synaptic parameters, we demonstrate that a circuit can not only produce all conventional modes, it can easily switch between these modes by introducing brief external current stimuli to some of the neurons or by changing the synaptic parameters. The multistable modes that such a simple ring circuit can generate, and the ease with which it switches between the modes, indicate that such a simple circuit may serve as a useful example in modeling many different types of biological central pattern generators