Sleep shapes hippocampal representations towards enhanced pattern separation and completion

• Applicants: Professor Dr. Thorsten Bartsch; Professor Andrea Burgalossi, Ph.D.
• Subject Area: Cognitive, Systems and Behavioural Neurobiology ; Biological Psychology and Cognitive Neuroscience
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 468645090

This project investigates the hypothesis that sleep shapes newly encoded hippocampal representations via their reactivation such that hippocampal operations of pattern separation and completion become enhanced. We will test this hypothesis in a translational cross-species approach in humans and mice. In humans, we rely on behavioral mnemonic similarity tasks that reliably reflect hippocampal pattern separation and completion processes in combination with functional neuroimaging. In rodents, we will measure hippocampal place cell activity for similar and dissimilar environments, and use place-cell remapping as a readout for pattern completion and separation at the network level. We aim, in both species, (i) to show enhancing effects of sleep on pattern separation/completion that are associated with specific activations in hippocampal fMRI and place cell networks, respectively. Moreover, in both species, we will examine whether the enhancing effects of sleep on pattern separation/completion (ii) is caused by memory reactivations during sleep (using targeted memory reactivation procedures), and (iii) critically depends on slow oscillations (using auditory closed-loop stimulation procedures). Finally (iv), we will scrutinize the hypothesized causal influence of reactivations of hippocampal place cell memory during sleep on remapping indicators of pattern separation/completion, combining closed‐loop optogenetic interventions with engram-tagging techniques in mice. In specifying the fate of newly encoded hippocampal representations during sleep, our project addresses a key issue of this Research Unit.

• DFG Programme: Research Units
• Subproject of: FOR 5434: Information Abstraction During Sleep