A hippocampal model for episodic memory using neurogenesis and asymmetric STDP

Our memory is first acquired as memory of a personal event (episodic memory). Then, its temporal context is removed and the resultant memory is used in higher-order information processing, such as thinking, reasoning and so on. Therefore, episodic memory is the basis of our memories. In this paper, we propose an episodic memory model which adopts the physiological findings of the hippocampus. Episodic memory can be regarded as a temporal sequence of patterns. In general, such a sequence may have some patterns which appear several times in it, or plural temporal sequences may share some same patterns with each other. That is, it is indispensable for the episodic memory model to handle one-to-many association and context. In the proposed model, the neurogenesis in dentate gyrus (DG) contributes to build different representations in CA3 for the same input patterns, and facilitates one-to-many association. Moreover, the asymmetric spike timing dependent synaptic plasticity introduced to the learning of recurrent collateral in CA3 enables memory of context. Computer simulation results show that the proposed model can deal with complex temporal sequences.