THE MECHANISM OF THE SHADOW REFLEX IN CIRRIPEDIA III. RHYTHMICAL PATTERNED ACTIVITY IN CENTRAL NEURONS AND ITS MODULATION BY SHADOWS

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Abstract
Isolated and semi-intact preparations of the CNS of the rock barnacle Balanus cariosus (Pallas) were used to explore the activity of neurons concerned with the fishing behavior and the shadow reflex in the sessile animal. Two classes of rhythmically bursting neurons were identifiable by location, bursting pattern and response to "light off" that exhibit reciprocity. Evidence is presented to link the laterally located bursters (excited at "light off") to withdrawal, and the mid-line bursters (inhibited at "light off") to extension, in the intact animal. Bursters are driven and/or modulated by synaptic input, as shown by non-spiking bursters when current is passed and by treating the ganglion with high Mg2+, low Ca2+ artificial sea water. In some bursters, synchronization is accomplished by a common antecedent interneuron. Simultaneous neuron-muscle recordings and locating axons of impaled neurons in peripheral nerves established some bursters as motor neurons.