How the Prefrontal Cortex Helps Store Memories Consistent with What We Already Know

What is it about?

Why can’t you remember where you left your keys but still know every word of your favorite childhood song? It has been long established that recent events stored in our short-term memory, and past events stored in our long-term memory are each controlled by distinct (connected) parts of the brain. According to the Complementary Learning Systems theory, during wakefulness the hippocampus quickly stores memories by changing the connections between the neurons forming a labile memory engram. Posteriorly, during sleep, memories are transferred to the prefrontal cortex (PFC), its long-term storage site. Recent experiments, however, suggest that the PFC might have a broader role than previously considered, with lesions in the PFC disrupting the encoding of familiar events in the HPC. Additionally, it has been shown that events can be rapidly consolidated in PFC during wakefulness provided it is congruent with previously acquired knowledge. In this study we show how the PFC uses stored memory ‘schemas’ consolidated during previous experiences to identify compatible information, quickly incorporate it into its network, and uses inhibitory long-range projections to gate which components of the incoming information are encoded in the hippocampus. We suggest that this top-down inhibition of hippocampal activity may be responsible for the sparse activity observed in the hippocampus during the encoding of congruent events, ultimately avoiding interference of partially overlapping memories and increasing the hippocampus capacity of short-term storage.

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Photo by Roman Kraft on Unsplash

Photo by Roman Kraft on Unsplash