Researchers from the University of California, Irvine have identified a previously unknown source of two key brain waves essential for deep sleep – slow waves and sleep spindles. These brain waves are traditionally believed to originate from a brain circuit connecting the thalamus and cortex, but the team’s findings suggest that the axons in the memory centers of the hippocampus also play a significant role. The study, published in Scientific Reports, challenges existing theories about the generation of these brain waves and sheds new light on the role of the hippocampus in memory processing during sleep.
For decades, slow waves and sleep spindles have been recognized as crucial components of deep sleep, typically measured through electroencephalography recordings on the scalp. The UC Irvine-led team’s research discovered that these brain waves can originate from axons within the hippocampus’s cornu ammonis 3 region and can be measured in single axons. This finding suggests that slow waves and sleep spindles are generated independently of neuronal spiking activity, providing new insights into the brain’s activity during deep sleep.
Utilizing innovative techniques such as in vitro reconstructions of hippocampal subregions and microfluidic tunnels for single axon communication, the team observed spontaneous spindle waves in isolated hippocampal neurons. These findings indicate that spindle oscillations originate from active ion channels within axons, rather than through volume conduction as previously believed. The discovery of spindle oscillations in single hippocampal axons opens new possibilities for understanding the mechanisms underlying memory consolidation during sleep.
The research team, including lead author Mengke Wang, Gregory Brewer, William Tang, Bryce Mander, and Samuel Lassers, received financial support from the UCI Foundation for their study. Brewer, who also has affiliations with the Institute for Memory Impairment and Neurological Disorders and the Center for Neurobiology of Learning and Memory, emphasized the significant implications of these findings for sleep research. Understanding the hippocampus’s role in generating slow waves and sleep spindles expands our knowledge of the brain’s activity during deep sleep and its impact on memory processing, paving the way for future studies on targeting hippocampal activity for improving sleep quality and cognitive function.
Overall, the study uncovers a previously unrecognized aspect of deep sleep brain activity and highlights the importance of the hippocampus in generating slow waves and sleep spindles. These findings provide a promising foundation for further research on the therapeutic potential of targeting hippocampal activity to enhance sleep quality and cognitive function. The discovery of these brain waves’ source within the hippocampus challenges traditional theories and offers new insights into how the brain supports memory processing during sleep, suggesting potential new approaches for treating sleep-related disorders.