Parametric Features of Inhibition of Feeding in Aplysia by Associative Learning, Satiation, and Sustained Lip Stimulation

In order to determine whether different classes of behavioral plasticity affect common or unique neural loci, the effects of three types of processes that inhibit feeding in Aplysia were quantified. Changes in feeding behavior due to an associative learning task in which animals learn that food is inedible were compared with behavioral effects caused by satiation and by sustained lip stimulation. The data indicate that each process modifying feeding can be characterized by differences in time to stop responding to food, by differences in specificity of the decrement to a particular food, and by different patterns of motor output before complete cessation of responsiveness. The data suggest each process inhibiting feeding acts at a different neural site. Learning that food is inedible may be due to facilitation of a specific sensory pathway onto pattern generators producing rejection responses. Sustained lip stimulation seems to inhibit feeding by causing a decrement in all outputs of a particular sensory pathway. Finally, satiation appears to represent inhibition of feeding motor elements.