Hippocampal two-stage Learning and Memory Consolidation

We present a neural network model of consolidation focussing on the possible functional roles of theta-and sharp-wave-periods in hippocampal EEG-recordings of rats. Our network implements ideas suggested by Buzss aki concerning two tentative stages of learning in the hippocampal formation: sparse assemblies in region CA3 are weak and transiently potentiated during theta-related exploratory behavior; longer lasting potentiation is mediated by strong arhythmical population bursts (SPW) reactivating the most recently excited assemblies during consummatory behavior. The network reproduces typical signal forms found in experiments. We show that the proposed two-stage mechanism requires some form of`cell'-facilitation in the theta-phase; potentiation of synapses only is not suucient.