ACTIVITY IN A CRUSTACEAN GANGLION. II. PATTERN AND INTERACTION IN BURST FORMATION

¹ Biological Laboratories, Harvard University, Cambridge, Mass.; Marine Biological Laboratory, Woods Hole, Mass.; University of California, Los Angeles, Calif.

1. The pattern of nervous activity in a spontaneously active nerve center containing only nine neurons, the cardiac ganglion of the lobster, is described. This pattern is a burst of large and small nerve impulses, each neuron firing several times during the burst, followed by a lengthy silent period.

2. When isolated, single large neurons tend to fire spontaneously at a constant frequency several times greater than normal burst frequency. It is suggested that the rhythmic burst derives from such spontaneity by a reciprocal interaction among the ganglion units which produces alternating periods of high synaptic excitation and post-excitatory depression.

3. Large, rapidly conducted impulses originating in the five large ganglion cells cause the rapid contraction of the heart muscle. Smaller, slower impulses arising in the four small ganglion cells produce no noticeable motor response, but increase activity in the large neurons. Both large and small cells seem to function as pacemakers, interneurons, and possibly as stretch receptors as the occasion demands.

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