Spatial mnemonic encoding: theta power decreases and medial temporal lobe BOLD increases co-occur during the usage of the method of loci

Fellner, M.-C., Volberg, G., Wimber, M. , Goldhacker, M., Greenlee, M. W. and Hanslmayr, S. (2016) Spatial mnemonic encoding: theta power decreases and medial temporal lobe BOLD increases co-occur during the usage of the method of loci. eNeuro, 3(6), (doi: 10.1523/ENEURO.0184-16.2016) (PMID:28101523) (PMCID:PMC5223054)

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The method of loci is one, if not the most, efficient mnemonic encoding strategy. This spatial mnemonic combines the core cognitive processes commonly linked to medial temporal lobe (MTL) activity: spatial and associative memory processes. During such processes, fMRI studies consistently demonstrate MTL activity, while electrophysiological studies have emphasized the important role of theta oscillations (3–8 Hz) in the MTL. However, it is still unknown whether increases or decreases in theta power co-occur with increased BOLD signal in the MTL during memory encoding. To investigate this question, we recorded EEG and fMRI separately, while human participants used the spatial method of loci or the pegword method, a similarly associative but nonspatial mnemonic. The more effective spatial mnemonic induced a pronounced theta power decrease source localized to the left MTL compared with the nonspatial associative mnemonic strategy. This effect was mirrored by BOLD signal increases in the MTL. Successful encoding, irrespective of the strategy used, elicited decreases in left temporal theta power and increases in MTL BOLD activity. This pattern of results suggests a negative relationship between theta power and BOLD signal changes in the MTL during memory encoding and spatial processing. The findings extend the well known negative relation of alpha/beta oscillations and BOLD signals in the cortex to theta oscillations in the MTL.

Item Type:Articles
Additional Information:This research was supported by Deutsche Forschungsgemeinschaft Grant 501100001659 HA 5622/1-1 (to S.H.).
Glasgow Author(s) Enlighten ID:Hanslmayr, Professor Simon and Wimber, Professor Maria
Authors: Fellner, M.-C., Volberg, G., Wimber, M., Goldhacker, M., Greenlee, M. W., and Hanslmayr, S.
College/School:College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
Journal Name:eNeuro
Publisher:Society for Neuroscience
ISSN (Online):2373-2822
Published Online:21 December 2016
Copyright Holders:Copyright © 2016 Fellner et al.
First Published:First published in eNeuro 3(6): 0184-16.2016
Publisher Policy:Reproduced under a Creative Commons License

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