title: Spatial Mnemonic Encoding: Theta Power Decreases and Medial Temporal Lobe BOLD Increases Co-Occur during the Usage of the Method of Loci.
abstract: 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.
authors.affiliation: Department of Psychology, University of Konstanz, 78457 Konstanz, Germany; Department of Neuropsychology, Institute of Cognitive Neuroscience, Ruhr University Bochum, 44801 Bochum, Germany.
authors.forename: Marie-Christin
authors.identifier: 0000-0001-6639-9833
authors.initials: MC
authors.lastname: Fellner
authors.affiliation: Institute of Experimental Psychology, University of Regensburg , 93040 Regensburg, Germany.
authors.forename: Gregor
authors.initials: G
authors.lastname: Volberg
authors.affiliation: School of Psychology, University of Birmingham , Birmingham B15 2TT, United Kingdom.
authors.forename: Maria
authors.identifier: 0000-0002-1917-353X
authors.initials: M
authors.lastname: Wimber
authors.affiliation: Institute of Experimental Psychology, University of Regensburg , 93040 Regensburg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Goldhacker
authors.affiliation: Institute of Experimental Psychology, University of Regensburg , 93040 Regensburg, Germany.
authors.forename: Mark W
authors.identifier: 0000-0003-2305-9286
authors.initials: MW
authors.lastname: Greenlee
authors.affiliation: School of Psychology, University of Birmingham , Birmingham B15 2TT, United Kingdom.
authors.forename: Simon
authors.initials: S
authors.lastname: Hanslmayr
mesh_terms: D000293:Adolescent; D000328:Adult; D001245:Association Learning / Q000502:physiology; D001931:Brain Mapping; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004569:Electroencephalography; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory / Q000502:physiology*; D009483:Neuropsychological Tests; D010100:Oxygen / Q000097:blood*; D013028:Space Perception / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology*; D013826:Theta Rhythm / Q000502:physiology*; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: EEG; fMRI; memory encoding; method of loci; mnemonics; theta oscillations