Science
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We studied the contribution of the Aplysia peripheral nervous system, in the siphon and gill, to habituation of the gill withdrawal reflex. After removal of one central ganglion, the parietovisceral, repeated stimulation of the siphon caused habituation of the reflex as it had with the ganglion intact, showing that there is a peripheral pathway between the siphon and gill with competence to mediate habituation. ⋯ Also, stimulation of one nerve dishabituates the withdrawal movements elicited by the other. These identify two sites of habituation in the gill in addition to sites in the parietovisceral ganglion.