Hippocampal Replay of Extended Experience

• Main Authors: Davidson, Thomas J. (Contributor), Kloosterman, Fabian (Contributor), Wilson, Matthew A. (Contributor)
• Other Authors: Massachusetts Institute of Technology. Department of Brain and Cognitive Sciences (Contributor), Picower Institute for Learning and Memory (Contributor)
• Format: Article
• Language: English
• Published: Elsevier B.V., 2015-03-31T20:57:50Z.
• Subjects: Article
• Online Access: Get fulltext

During pauses in exploration, ensembles of place cells in the rat hippocampus re-express firing sequences corresponding to recent spatial experience. Such "replay" co-occurs with ripple events: short-lasting (∼50-120 ms), high-frequency (∼200 Hz) oscillations that are associated with increased hippocampal-cortical communication. In previous studies, rats exploring small environments showed replay anchored to the rat's current location and compressed in time into a single ripple event. Here, we show, using a neural decoding approach, that firing sequences corresponding to long runs through a large environment are replayed with high fidelity and that such replay can begin at remote locations on the track. Extended replay proceeds at a characteristic virtual speed of ∼8 m/s and remains coherent across trains of ripple events. These results suggest that extended replay is composed of chains of shorter subsequences, which may reflect a strategy for the storage and flexible expression of memories of prolonged experience.
Massachusetts Institute of Technology. Department of Brain and Cognitive Science (Singleton Fellowship)
National Institutes of Health (U.S.) (grant MH061976)