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Synchronization and phase-locking are relevant to many biological problems. For example, in photosensitive epilepsy, exposure to rhythmic bright lights can induce an outburst of synchronous brain activity resulting in a seizure. Phase-locking is also relevant to central patter generators (CPGs,) which are neural circuits that produce a repetitive pattern of motor activity such as locomotion or respiration. The stomatogastric ganglion (STG) of crustaceans coordinates the motor activity of the muscles of the stomach. The neurons of the STG produce a triphasic, oscillating pyloric rhythm, which causes sequences of contraction in stomach muscles. The effects of excitatory synaptic inputs on these pacemaker neurons can lead to an understanding of how neurons interact in a central pattern generator circuit. By dissecting and isolating the stomatogastric nerves of the lobster stomach, experiments may be performed by using the dynamic clamp to inject ramped and square artificial conductance pulses of varying amplitude and duration into the bursting pyloric dilator (PD) neuron of the ganglion. A phase response curve (PRC) can then be constructed. A PRC describes how the neuron reacts to these various inputs by depicting the change in period of the bursts that occurs after injection at different phases of the rhythm. PRCs are used to characterize how oscillators react to excitatory inputs. Since the lobster rhythm is relatively unstable, experiments on the STG of crabs were investigated and their rhythm was found to be much more stable. More data is currently being collected on these species.
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