Mapping Between Neural and Physical Activities of the Lobster Gastric Mill

A computer model of the musculoskeletal system of the lobster gastric mill was constructed in order to provide a behavioral interpretation of the rhythmic patterns obtained from isolated stomatogastric ganglion. The model was based on Hill's muscle model and quasi-static approximation of the skeletal dynamics and could simulate the change of chewing patterns by the effect of neuromodulators. 1 THE STOMATOGASTRIC NERVOUS SYSTEM The crustacean stomatogastric ganglion (STG) is a circuit of 30 neurons that controls rhythmic movement of the foregut. It is one of the best elucidated neural circuits. All the neurons and the synaptic connections between them are identified and the effects of neuromodulators on the oscillation patterns and neuronal characteristics have been extensively studied (Selverston and Moulins 1987, H arrisWarrick et al. 1992). However, STG's function as a controller of ingestive behavior is not fully understood in part because of our poor understanding of the controlled object: the musculoskeletal dynamics of the foregut. We constructed a mathematical model of the gastric mill, three teeth in the stomach, in order to predict motor patterns from the neural oscillation patterns which are recorded from the isolated ganglion. The animal we used was the Californian spiny lobster (Panulirus interruptus), which