Abstract
Sleep, specifically non-rapid eye movement (NREM) sleep, is thought to play a critical role in the consolidation of recent memories. Two main oscillatory activities observed during NREM, cortical slow oscillations (SO, 0.5–1.0Hz) and thalamic spindles (12–15Hz), have been shown to independently correlate with memory improvement. Yet, it is not known how these thalamocortical events interact, or the significance of this interaction, during the consolidation process. Here, we found that systemic administration of the GABAergic drug (zolpidem) increased both the phase-amplitude coupling between SO and spindles, and verbal memory improvement in humans. These results suggest that thalamic spindles that occur during transitions to the cortical SO Up state are optimal for memory consolidation. Our study predicts that the timely interactions between cortical and thalamic events during consolidation, contribute to memory improvement and is mediated by the level of inhibitory neurotransmission.
Highlights
New memories need to be transformed into more stable representations or they will be forgotten [1]
Verbal memory performance and sleep spindle density were significantly higher in zolpidem compared with placebo, spindle density decreased in sodium oxybate (1.965±1.317, p = .001), and no performance differences were found between sodium oxybate and placebo (p = .210), performance was numerically lower in the sodium oxybate condition [8]
We found no difference in power of spindle and slow oscillations (SOs) between placebo, zolpidem and sodium oxybate conditions
Summary
New memories need to be transformed into more stable representations or they will be forgotten [1]. The coordination of memory-related brain regions of hippocampus, neocortex, and thalamus, is thought to occur during NREM sleep [4] This sleep phase is characterized by thalamically-driven oscillatory activity called sleep spindles (12–15 Hz) and large amplitude, synchronized cortically-driven slow oscillations (SOs). Previous studies have observed a temporal coupling of spindles and SOs during NREM sleep [2], which increases following a memory task [11] These findings suggest that consolidation may benefit from appropriate coordination of these EEG features. The functional consequence of spindle and SO event coordination during Stage 2 sleep, is not known To address this question, we analyzed human EEG to determine the importance of a precise temporal relationship between SOs and spindles during NREM Stage 2 sleep for hippocampaldependent, declarative verbal memory performance. We compared the contributions of each electrophysiological event independently and coupled using regression models
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
