This application proposes, in part, to investigate how rhythmic motor patterns such as walking maintain proper timing relationships as overall cycle period changes, and whether individual synaptic connections can be shown to play specific roles in generating neural network activity. More complete understanding of these issues would advance our ability to treat motor pathologies and to design robotic devices to give these patients greater mobility and independence. It also proposes to investigate how rhythmic networks interact and how rhythmic input entrains endogenous oscillator networks. This work falls under the general rubric of neural oscillator function, and has significance to rhythmic motor pattern production, rhythmic sensory pattern interpretation, and the multiple oscillatory activities present in the central nervous system. Rhythmic behaviors such as locomotion, chewing, swallowing, and copulation are essential for individual and species survival. Breathing, heartbeat, and rhythmic gut peristalsis continue throughout an animal's existence. Many animal communications have a rhythmic nature (most highly developed in music), and small changes in cycle period or internal phasing can prevent call recognition. Multiple simultaneous rhythms are present in brain activity, and these rhythms change as a function of arousal and attention. Correct coordination and interaction among these multiple rhythms is essential for functional behavior. For instance, respiratory and Iocomotory rhythms are often coordinated. In locomotion the neural networks that produce the each limb's activity must be properly coordinated to generate a functional behavior, as must often be upper limb movements in bipeds. Changing from tonic to burst firing alters information transfer from thalamus to cortex, changes in bursting activity in the subthalamic nucleus-external globus pallidus network are associated with Parkinson's disease, and incorrect synchronization of central rhythmicity underlies epilepsy. The research will be performed in a well known model system, the pyloric neuromuscular system, with a proven track record of discovering neurobiological principles of wide applicability, including to humans. [unreadable] [unreadable]