Relationships between dishabituation, sensitization, and inhibition of the gill- and siphon-withdrawal reflex in Aplysia californica: effects of response measure, test time, and training stimulus.

Previous studies have raised questions about the relationships between habituation, dishabituation, sensitization, and inhibition of reflex responses. To explore this issue further, a systematic study of these simple forms of learning was carried out in unrestrained Aplysia in which the amplitude as well as the duration of both the gill- and siphon-withdrawal reflexes were measured after either tailshock or mantle shock. The results suggest that transient reflex inhibition is not an invariant effect of noxious stimulation but depends instead on the response measure, test time, and type of noxious stimulus. Furthermore, the results suggest that dishabituation and sensitization may not involve different processes at the behavioral level; rather the observed differences between them may be due largely to an interaction between habituation and inhibition.