Date: 30 Oct 2014

Associative Reactivation of Place–Reward Information in the Hippocampal–Ventral Striatal Circuitry

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Abstract

Thinking back to an exciting event often includes the scene in which the event took place. Associations between spatial locations and emotional events, such as obtaining rewards, are important for surviving in a changing environment and depend critically on communication between the hippocampus and ventral striatum. The potential contribution of subcortical brain areas such as the ventral striatum to memory consolidation has remained underexposed as the focus of consolidation research has been on the hippocampal–neocortical dialogue in declarative memory. This chapter highlights the cross-structural reactivation of place–reward information in the hippocampal–ventral striatal circuitry during sleep, an “off-line” process that is thought to contribute to memory consolidation by strengthening synapses between neurons activated in a preceding behavior. The reactivation process is temporally organized such that place information in the hippocampus is preferentially activated in advance of ventral striatal motivational information. This is consistent with the orchestrating role of the hippocampus predicted by consolidation theories. Neural representations are replayed on a compressed timescale, meaning that firing patterns of several seconds of real-time experience are reinstated in a time window of several hundreds of milliseconds. On this temporal scale, the reactivation of place–reward information may contribute to long-lasting changes in synaptic efficacy such as spike-timing dependent plasticity in hippocampal–ventral striatal connections. Cross-structural reactivation of place–reward information in the hippocampal–ventral striatal circuitry demonstrates the distributed way the brain processes, links, and retrieves different aspects of the memory.