Cellular Analysis of a Gastropod (Hermissenda Crassicornis) Model of Associative Learning

Intuitive formulations concerning the nature of cellular substrates for associative learning are considered. Invertebrate models of vertebrate learning are discussed. A cellular analysis of a long-term associative behavioral change is reviewed for the nudibranch mollusc Hermissenda crassicornis. Convergence of neuronal pathways which mediate natural sensory stimuli used for associative training have been determined. Primary biophysical changes within single identified neurons are analyzed for their causal role in learning behavior. A sequence of neural processes is proposed to underlie acquisition and retention of an associative behavioral change of Hermissenda. Paired sensory stimuli enhance voltage-dependent currents by means of converging sensory pathways. Repeated pairings cause progressive membrane depolarization, which in turn causes long-lasting conductance changes. Biochemical correlates of these phenomena are presented.