Model Analysis of Associative Learning in The Photoreceptor of Marine Mollusc, Hermissenda Crassicornis
A marine mollusc, Hermissenda Crassicornis, has an ability to learn the association of conditioned stimulus (CS) and unconditioned stimulus (UCS). In this learning, it was shown that some physiological changes, such as decrease of K+ conductances and a long lasting depolarization (LLD) after light stimulus, were caused in the type B photoreceptor (BPR). However, the underlying mechanism of these changes has not been exhibited experimentally yet. In this paper, a BPR model based on the ionic current and cytosolic Ca2+ mechanism was presented in order to reveal the relation of these phenomena. As a result of model simulation, it was suggested that LLD would not be mediated by K+ conductance changes, but by the change of cytosolic Ca2+ mechanism. Furthermore, it was shown that the dependency of inter-stimulus interval (ISI) between CS and UCS on the acquisition of memory could be yielded by an increase of cytosolic Ca2+ concentration in BPR.
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