Understanding how memory is encoded and maintained in our brain is paramount to understanding cognitive functions. Unlike in a computer, human memories are continuously consolidated, reconsolidated, and integrated within the context of what has already been learned. This process is thought to involve exchanges of information between the cortex and the hippocampus during sleep. The investigators will study the ability of small groups of cells in the rodent hippocampus and medial prefrontal cortex (mPFC) to become transiently co-active during sleep periods occurring many hours after learning has taken place. Rats will be engaged in learning tasks aimed at selectively activating one or both of these areas. It is expected that the activity recorded during post-task sleep will be correlated with the activity of the same cells during the task in a manner compatible with the nature of the task and the specifics of the learning. This type of reactivation is considered to be a basic mechanism for memory consolidation.
The investigators have developed new analytical tools based on fuzzy clustering and information geometry. Preliminary data show that short episodes of reactivation occur with different time courses in these two structures, as is often proposed on theoretical grounds. In this project, the investigators will study how this reactivation is coordinated across two connected brain areas (CA3-CA1, CA1-mPFC) on very long time scales, and how single neurons contribute to single reactivating episodes.
These studies will yield insights into the long-term temporal and spatial dynamics of reactivation in the adult rodent. They will also contribute to a better understanding of the neural basis of memory consolidation and reconsolidation in cortex and hippocampus, and the relationship between memory consolidation and sleep.
