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Independent delta/theta rhythms in the human hippocampus and entorhinal cortex

Mormann, Florian and Osterhage, Hannes and Andrzejak, Ralph G. and Weber, Bernd and Fernández, Guillén and Fell, Juergen and Elger, Christian E. and Lehnertz, Klaus (2008) Independent delta/theta rhythms in the human hippocampus and entorhinal cortex. Frontiers in Human Neuroscience, 15 (2). Art. No. 3. ISSN 1662-5161. PMCID PMC2525973. doi:10.3389/neuro.09.003.2008.

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Theta oscillations in the medial temporal lobe (MTL) of mammals are involved in various functions such as spatial navigation, sensorimotor integration, and cognitive processing. While the theta rhythm was originally assumed to originate in the medial septum, more recent studies suggest autonomous theta generation in the MTL. Although coherence between entorhinal and hippocampal theta activity has been found to influence memory formation, it remains unclear whether these two structures can generate theta independently. In this study we analyzed intracranial electroencephalographic (EEG) recordings from 22 patients with unilateral hippocampal sclerosis undergoing presurgical evaluation prior to resection of the epileptic focus. Using a wavelet-based, frequency-band-specific measure of phase synchronization, we quantified synchrony between 10 different recording sites along the longitudinal axis of the hippocampal formation in the non-epileptic brain hemisphere. We compared EEG synchrony between adjacent recording sites (i) within the entorhinal cortex, (ii) within the hippocampus, and (iii) between the hippocampus and entorhinal cortex. We observed a significant interregional gap in synchrony for the delta and theta band, indicating the existence of independent delta/theta rhythms in different subregions of the human MTL. The interaction of these rhythms could represent the temporal basis for the information processing required for mnemonic encoding and retrieval.

Item Type:Article
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URLURL TypeDescription
Mormann, Florian0000-0003-1305-8028
Additional Information:© 2008 Mormann, Osterhage, Andrzejak, Weber, Fernández, Fell, Elger and Lehnertz. This is an open-access article subject to an exclusive license agreement between the authors and the Frontiers Research Foundation, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited. Received: 25 January 2008; paper pending published: 08 April 2008; accepted: 06 May 2008; published online: 22 May 2008. We thank Christof Koch, Costas Anastassiou, Gyorgy Buzsaki, and Eva Pastalkova for fruitful discussion. This work was supported by the Intramural Research Fund BONFOR of the University of Bonn and the 6th Framework Programme of the European Commission (Marie Curie OIF 040445).
Funding AgencyGrant Number
Marie Curie Fellowship040445
University of BonnUNSPECIFIED
Subject Keywords:medial temporal lobe, intracranial EEG, oscillations, synchronization, wavelet, phase precession
Issue or Number:2
PubMed Central ID:PMC2525973
Record Number:CaltechAUTHORS:20090729-104548893
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14719
Deposited By: Ruth Sustaita
Deposited On:07 Aug 2009 20:51
Last Modified:08 Nov 2021 23:13

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