Frequency Control of a Rhythmic Network Through the Interaction of Both Fast and Slow Inputs

Rhythmic movements are often controlled by systems containing coupled subnetworks whose oscillations are of different frequencies. We show how fast inhibition from the pyloric network interacts with a slow modulatory input to control the frequency of the gastric mill rhythm of the crustacean stomatogastric ganglion. We deduce that the timing of the pyloric input is crucial in determining what affect it has on the frequency of the gastric network. Over one set of timings, the modulatory input and the pyloric input work together to determine the frequency and over another set of timings, the affect of the pyloric input is mitigated by the modulatory input.