Memory Consolidation: How Reliable Are Our Memories?

In the first part of this thesis, I evaluate the contribution of sleep on memory representations of an object/place memory in young and old animals. I demonstrate that different subpopulations of cells code distinct aspects of the mnemonic experience and an acute session of sleep deprivation serves to improve cognitive performance in old mice, while producing impairments in young ones. Analysis of sleep patterns demonstrate that improved memory in old mice correlates with consolidated SWS, demonstrating that acute sleep deprivation has different effects in young and old mice. In the second part of this thesis, I evaluate the stability of cortical memory engrams, the changes associated with memory retrieval, and the reorganization of cortical networks over time. The results demonstrate that constitutively active neurons – neurons active across retrieval sessions -carry the emotional valence of learned cues, allowing discrimination of safe and fearful memory traces, whereas temporary active neurons generalize representations at the neural level.