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Nat Neurosci. 2015 Nov;18(11):1679-1686. doi: 10.1038/nn.4119. Epub 2015 Sep 21.

Hierarchical nesting of slow oscillations, spindles and ripples in the human hippocampus during sleep.

Author information

1
School of Psychology, University of Birmingham, Birmingham, UK.
2
MRC Cognition and Brain Sciences Unit, Cambridge, UK.
3
Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, NL.
4
Institute of Psychology, Christian-Albrechts-University of Kiel, Kiel, Germany.
5
Department of Epileptology, University of Bonn, Bonn, Germany.
6
German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany.
7
Department of Neuropsychology, Institute of Cognitive Neuroscience, Ruhr University Bochum, Germany.
#
Contributed equally

Abstract

During systems-level consolidation, mnemonic representations initially reliant on the hippocampus are thought to migrate to neocortical sites for more permanent storage, with an eminent role of sleep for facilitating this information transfer. Mechanistically, consolidation processes have been hypothesized to rely on systematic interactions between the three cardinal neuronal oscillations characterizing non-rapid eye movement (NREM) sleep. Under global control of de- and hyperpolarizing slow oscillations (SOs), sleep spindles may cluster hippocampal ripples for a precisely timed transfer of local information to the neocortex. We used direct intracranial electroencephalogram recordings from human epilepsy patients during natural sleep to test the assumption that SOs, spindles and ripples are functionally coupled in the hippocampus. Employing cross-frequency phase-amplitude coupling analyses, we found that spindles were modulated by the up-state of SOs. Notably, spindles were found to in turn cluster ripples in their troughs, providing fine-tuned temporal frames for the hypothesized transfer of hippocampal memory traces.

PMID:
26389842
PMCID:
PMC4625581
DOI:
10.1038/nn.4119
[Indexed for MEDLINE]
Free PMC Article

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