Development assembly of learning in Aplysia.

Development can provide a powerful analytic approach for distinguishing and analysing specific behavioral, cellular and molecular processes as they emerge during ontogeny. Recently, such a developmental strategy has been used to investigate the functional assembly of different forms of non-associative learning (habituation, dishabituation and sensitization) in the marine mollusc Aplysia. This analysis has shown that different forms of learning, as well as their cellular analogs at central synapses, emerge according to very different developmental timetables. Subsequent behavioral studies in adult Aplysia showed that these same forms of learning were also clearly dissociable in the mature animal. These results, taken with earlier studies, suggest that a commonly held 'dual-process' view of non-associative learning, which attempts to account for all forms of non-associative learning as the interaction of only two processes (one decremental and one incremental) requires revision, and that a multi-process view, which includes the possibility of inhibitory as well as facilitatory interactions, is required to account adequately for all of the behavioral features of nonassociative learning.