Directed functional connectivity between neocortex and mediotemporal lobe during different sleep stages
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1
University of Bonn, Germany
The problem of directional coupling between cortical and mediotemporal structures in dependence of various sleep stages is controversially discussed in recent publications. While several authors have suggested that a hippocampal-neocortical replay of previously stored information occurs during sleep (e.g. Buzsaki. 1998), others suppose that the hippocampus is always mainly driven by neocortical areas (e.g. Tononi et al. 2006). Addressing this issue, we studied directional relationships of couplings in EEG of 10 patients undergoing presurgical evaluation with mediotemporal depth electrodes. For each patient, electrode contacts from the anterior and posterior hippocampus, the rhinal cortex, as well as from scalp position C3/C4 were entered into the analysis. Directionality for different channel combinations was quantified using a bivariate measure, which is based on phase synchronization (Rosenblum and Pikovsky 2001). This method investigates functional dependencies between two phases by deducing interactions from Fourier series, which were fitted to phase increments in dependence of both phases. Sleep stages were classified based on scalp EEG, EMG and EOG recordings according to standard criteria (Rechtschaffen and Kales 1968). We observed that the rhinal cortex drives the neocortex across all sleep stages. However, the coupling between rhinal cortex and anterior hippocampus depended on sleep stage. While the rhinal cortex influences the anterior hippocampus during slow wave sleep (stages 3 and 4), the direction of this mutual coupling reverses during REM sleep. Our data question existing models of hippocampal-neocortical interaction and suggest that the rhinal cortex serves as a control region influencing both, hippocampal and neocortical areas.
References
1. Buzsaki G, Memory consolidation during sleep: a neurophysiological perspective, J. Sleep Res., 7 Suppl.1, 1998
2. Tononi G, Massimini M, Riedner BA, Sleepy Dialogues between Cortex and Hippocampus: Who Talks to Whom?, Neuron, 52:748-749, 2006
3. Rosenblum MG, Pikovsky AS, Detecting direction of coupling in interacting oscillators, Phys. Rev. E., 64:045202(R), 2001
4. Rechtschaffen, Kales, (Eds.) A manual of standardized terminology, techniques, and scoring system for sleep stages of human subjects. Public Health Service, 1968
Conference:
10th International Conference on Cognitive Neuroscience, Bodrum, Türkiye, 1 Sep - 5 Sep, 2008.
Presentation Type:
Poster Presentation
Topic:
Neuroinformatics of Cognition
Citation:
Wagner
T,
Axmacher
N,
Kranz
T,
Elger
C and
Fell
J
(2008). Directed functional connectivity between neocortex and mediotemporal lobe during different sleep stages.
Conference Abstract:
10th International Conference on Cognitive Neuroscience.
doi: 10.3389/conf.neuro.09.2009.01.372
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Received:
15 Dec 2008;
Published Online:
15 Dec 2008.
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Correspondence:
Tobias Wagner, University of Bonn, Bonn, Germany, twagner@uni-bonn.de