Frequency control of a slow oscillatory network by a fast rhythmic input: pyloric to gastric mill interactions in the crab stomatogastric nervous system

Abstract

The stomatogastic nervous system of the crab, Cancer borealis, produces a slow gastric mill rhythm and a fast pyloric rhythm. When the gastric mill rhythm is not active, stimulation of the modulatory commissural ganglion neuron 1 (MCN1) activates a gastric mill rhythm in which the lateral gastric (LG) neuron fires in antiphase with interneuron 1 (Int1). We present theoretical and experimental data that indicate that the period of the MCN1 activated gastric mill rhythm depends on the strength and time course of the MCN1 evoked slow excitatory synaptic potential (EPSP) in the LG neuron, and on the strength of inhibition of Int 1 by the pacemaker of the pyloric network. This work demonstrates a new mechanism by which a slow network oscillator can be controlled by a much faster oscillatory neuron or network and suggests that modulation of the slow oscillator can occur by direct action on the neurons and synapses of the slow oscillator, or indirectly by actions on the fast oscillator and its synaptic connection with the slow oscillator.