CRCNS: The noradrenergic modulation during sleep: from circuits to memory

About This Grant

PROJECT SUMMARY (See instructions): The ultimate goal of this research is to understand how brain rhythms during Non-Rapid Eye Movement (NREM) sleep relate to the replay of information encoded in the hippocampus, the subsequent transfer of that information into cortical long-term memory, and how these processes are modulated by the Locus Coeruleus (LC). Interplay during NREM sleep between cortical slow oscillations (SOs), thalamic spindles, and hippocampal sharp wave-ripples (SWRs) is crucial for transferring information into long-term memory. Both normal aging and Alzheimer's disease (AD) alter temporal properties of the dominant NREM sleep rhythms: sos, spindles, and SWRs. A key discovery in recent years is that these innate brain rhythms can be modulated by neuromodulatory centers, especially the Locus Coeruleus (LC). While recent studies, including those by the Pis of this project, have advanced our understanding of how the dynamic interplay between the cortex, thalamus, and hippocampus facilitates information transfer and memory consolidation, many essential questions about the LC's role in orchestrating thalamo-cortico-hippocampal activity during NREM sleep and its influence on sleep-dependent memory consolidation remain. We aim to tackle these questions by developing computational models tested and refined through electrophysiological and behavioral experiments in rats, along with spatially and temporally specific activation of LC neurons. Our central hypothesis is that memory consolidation processes are orchestrated by the precise timing of slow oscillations, spindles, and SWRs, and that norepinephrine (NE) release from LC neuron forebrain terminals can augment this coupling. We will test these hypotheses by combining multi-site electrophysiological recordings, circuit-selective optogenetic stimulation, behavioral assessments of memory, and the development of advanced computational models. The model-guided modulation patterns of LC activity during post-learning NREM sleep will demonstrate a causal relationship between LC-NE activity and the efficiency of sleep-dependent memory consolidation. Exploring how neuromodulation influences sleep and memory could lead to the development of novel clinical tools to mitigate cognitive dysfunctions in normal aging and AD, as well as new approaches to enhance learning. Since neuromodulatory system decline or dysfunction often heralds psychiatric and neurological diseases, pinpointing neurophysiological indicators of such dysregulation could aid in early intervention.