This research proposal’s goal is to investigate the role of cortico-hippocampal interactions during the encoding and consolidation of a memory. Current memory consolidation models postulate that memory storage in our brains occurs by a dynamic process- a recent episodic experience is initially encoded in the hippocampus, and during off-line states such as sleep, the encoded memory is gradually transferred to neocortex for long-term storage. One potential neural mechanism by which this could occur is replay, a phenomenon where neural activity patterns in the hippocampus evoked by a previous experience reactivate spontaneously during non-REM sleep, leading to coordinated cortical reactivation. While previous work suggests that hippocampal replay is important for encoding new memories, how memory consolidation is accomplished through cortico-hippocampal interactions is not well understood.This research project has three major aims- 1) examine how cortical feedback influences which spatial trajectory is replayed by the hippocampus, 2) investigate how the hippocampal replay of a behavioural episode modifies cortical circuits, 3) measure the causal role of cortico-hippocampal interactions in consolidating memories. We will record ensemble activity from freely moving rats during an auditory-spatial association task and during post-behavioural sleep sessions. We will focus our ensemble recordings on two brain regions: 1) the dorsal CA1 region of the hippocampus, where the phenomenon of sleep replay has been most extensively examined, and 2) auditory cortex, a region of the brain critical for both auditory perception and long-term memory storage. This work will use behavioral and molecular-genetic techniques in combination with large-scale electrophysiological recordings, to help elucidate the role of cortico-hippocampal interactions in memory encoding and consolidation.