Regional Slow Waves and Spindles in Human Sleep

Abstract

SUMMARY The most prominent EEG events in sleep are slow waves, reflecting a slow (<1 Hz) oscillation between up and down states in cortical neurons. It is unknown whether slow oscillations are synchronous across the majority or the minority of brain regions—are they a global or local phenomenon? To examine this, we recorded simultaneously scalp EEG, intracerebral EEG, and unit firing in multiple brain regions of neurosurgical patients. We find that most sleep slow waves and the underlying active and inactive neuronal states occur locally. Thus, especially in late sleep, some regions can be active while others are silent. We also find that slow waves can propagate, usually from medial prefrontal cortex to the medial temporal lobe and hippocampus. Sleep spindles, the other hallmark of NREM sleep EEG, are likewise predominantly local. Thus, intracerebral communication during sleep is constrained because slow and spindle oscillations often occur out-of-phase in different brain regions.

Thalamocortical synchronization during induction and emergence from propofol-induced unconsciousness

“…S6), δ oscillations are coherent between cortex and thalamus. This suggests that slow oscillations might be generated locally in different regions of cortex or thalamus (22,24,52,53), whereas δ oscillations involve interactions between cortex and thalamus (54,55). Overall, our results suggest that propofol can induce a variety of dynamics that mediate functional impairment of both cortical and thalamocortical circuits.…”

Sleep spindles are locally modulated by training on a brain–computer interface

“…If spindles are truly the carriers of memory consolidation, then they must act specifically on local circuits. Recent reports that spindles can occur independently in different medial brain areas suggest that spindles may have more of a local component than previously thought (20). Even so, these data cannot speak to whether spindles are localized within brain areas or whether local groups of spindles are specifically modulated by behavior.…”

Rhythmic alternating patterns of brain activity distinguish rapid eye movement sleep from other states of consciousness

“…Although fluctuations at these frequencies-roughly between 0.1 and 0.01 Hz-are typically described in the BOLD signal at rest (15, 16), they are not BOLD-specific, and have been consistently detected with other dynamic measures of brain activity, including EEG (17) and MEG (18); these occur during sleep (19,20) and persist into REM (21) (SI Text, Note 8). Interestingly, these fluctuations occur at the same temporal scale as a number of the other phasic phenomena that have been identified during REM (SI Text, Note 9).…”