Abstract

Central pattern generating neuronal networks (CPGs) control and coordinate rhythmic tasks such as swimming, breathing, and walking. We investigate whether biophysical properties of ionic currents could support multiple functional bursting regimes in neuronal models and provide efficient mechanisms of operation of multifunctional CPGs. Here we investigated whether the idea of multistable CPGs could be applied to two rhythmic behaviors in the cat: walking and paw shake. Both behaviors can be elicited in a spinalized cat, and there have been conflicting evidence that the same circuitry could be used for rhythmic behaviors with two distinct frequencies. We have developed a parsimonious model of a half-center oscillator composed of two mutually inhibitory neurons.  The model exhibits multistability of slow and fast bursting regimes: a fast, 7-10 Hz paw-shake rhythm and a slow, 1-2 Hz walking rhythm. It is possible to switch between paw shaking and walking regimes by pulses of conductance such as those that could come from sensory neurons in the paw or from higher centers of motor control. Our model explains new experimental data from Dr. Prilutsky Laboratory and suggests that a paw-shake response could be a transient activity of the multifunctional locomotion CPG.