Effect of Electrical Synapses in the Cycle-by-Cycle Period and Burst Duration of Central Pattern Generators

Abstract

Central Pattern Generators (CPGs) are neural circuits that generate robust coordinated neural activity to control motor rhythms. Many CPGs are convenient neural circuits for locomotion control in autonomous robots. In this context, invertebrate CPGs are key networks to understand rhythm generation and coordination, as their cells and connections can be identified and mapped, like in the crustacean pyloric CPG. Experiments during the last decades have shown that mutual inhibition by chemical synapses together with electrical coupling underlie the timing of neuron activations that shape each rhythm cycle of this CPG. Due to the presence of inhibitory and electrical synapses, regular and irregular triphasic spiking-bursting activity can be found in the pyloric CPG, always preserving the same neuron activation sequence. In this study, we use a model of this well-known CPG to assess the role of electrical synapses in shaping the cycle-by-cycle period and individual cell burst duration. We show that electrical coupling strength asymmetrically affects the burst duration of each individual neuron, as well as the overall cycle-by-cycle duration. Our results support the view that electrical coupling largely contributes to shape the intervals that define functional sequences in CPGs, which can be applied in bioinspired autonomous robotic motor control.