Winter 2015

Sleep, Memory & Brain Rhythms

Brendon O. Watson and György Buzsáki

Sleep occupies roughly one-third of our lives, yet the scientific community is still not entirely clear on its purpose or function. Existing data point most strongly to its role in memory and homeostasis: that sleep helps maintain basic brain functioning via a homeostatic mechanism that loosens connections between overworked synapses, and that sleep helps consolidate and re-form important memories. In this review, we will summarize these theories, but also focus on substantial new information regarding the relation of electrical brain rhythms to sleep. In particular, while REM sleep may contribute to the homeostatic weakening of overactive synapses, a prominent and transient oscillatory rhythm called “sharp-wave ripple” seems to allow for consolidation of behaviorally relevant memories across many structures of the brain. We propose that a theory of sleep involving the division of labor between two states of sleep–REM and non-REM, the latter of which has an abundance of ripple electrical activity–might allow for a fusion of the two main sleep theories. This theory then postulates that sleep performs a combination of consolidation and homeostasis that promotes optimal knowledge retention as well as optimal waking brain function.

BRENDON O. WATSON is a clinical psychiatrist and a research fellow at Weill Cornell Medical College at Cornell University and is doing postdoctoral research work at the Buzsáki Lab at the New York University School of Medicine. His research interests include sleep mechanisms and emotional processing in animal models and his clinical interests include affective and personality disorders. He has published in such journals as Dialogues in Clinical Neuroscience, Frontiers in Neuroscience, Frontiers in Neural Circuits, and Neuron.

GYÖRGY BUZSÁKI is the Biggs Professor of Neural Sciences at the New York University School of Medicine. His laboratory's research goal is to investigate syntactical structures that enable internal communication within the brain. He is among the top 1 percent of the most cited authors in neuroscience, the recipient of the 2011 Brain Prize, and the author of Rhythms of the Brain (2006). He also sits on the editorial board of numerous journals, including Science and Neuron.

To read this essay or subscribe to Dædalus, visit the Dædalus access page
Access now