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Neuroimage. 2016 Jul 1;134:607-616. doi: 10.1016/j.neuroimage.2016.04.031. Epub 2016 Apr 18.

Spindle activity phase-locked to sleep slow oscillations.

Author information

1
Institute for Medical Psychology and Behavioral Neurobiology, University of Tübingen, 72076 Tübingen, Germany; Graduate School of Neural and Behavioural Sciences, University of Tübingen, 72074 Tübingen, Germany; Centre for Integrative Neuroscience, University of Tübingen, 72076 Tübingen, Germany. Electronic address: jens.klinzing@uni-tuebingen.de.
2
Center of Brain, Behavior and Metabolism, University of Lübeck, 23562 Lübeck, Germany.
3
Institute for Medical Psychology and Behavioral Neurobiology, University of Tübingen, 72076 Tübingen, Germany; Centre for Integrative Neuroscience, University of Tübingen, 72076 Tübingen, Germany.
4
Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
5
Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany; Hoffmann-La Roche Ltd., Pharma Research and Early Development, 4070 Basel, Switzerland.

Abstract

The <1Hz slow oscillation (SO) and spindles are hallmarks of mammalian non-rapid eye movement and slow wave sleep. Spindle activity occurring phase-locked to the SO is considered a candidate mediator of memory consolidation during sleep. We used source localization of magnetoencephalographic (MEG) and electroencephalographic (EEG) recordings from 11 sleeping human subjects for an in-depth analysis of the temporal and spatial properties of sleep spindles co-occurring with SOs. Slow oscillations and spindles were identified in the EEG and related to the MEG signal, providing enhanced spatial resolution. In the temporal domain, we confirmed a phase-locking of classical 12-15Hz fast spindle activity to the depolarizing SO up-state and of 9-12Hz slow spindle activity to the up-to-down-state transition of the SO. In the spatial domain, we show a broad spread of spindle activity, with less distinct anterior-posterior separation of fast and slow spindles than commonly seen in the EEG. We further tested a prediction of current memory consolidation models, namely the existence of a spatial bias of SOs over sleep spindles as a mechanism to promote localized neuronal synchronization and plasticity. In contrast to that prediction, a comparison of SOs dominating over the left vs. right hemisphere did not reveal any signs of a concurrent lateralization of spindle activity co-occurring with these SOs. Our data are consistent with the concept of the neocortical SO exerting top-down control over thalamic spindle generation. However, they call into question the notion that SOs locally coordinate spindles and thereby inform spindle-related memory processing.

KEYWORDS:

Electroencephalography; Magnetoencephalography; Sleep; Slow oscillation; Source localization; Spindle

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