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Alpha Rhythms Reveal When and Where Item and Associative Memories Are Retrieved.

Published version
Peer-reviewed

Type

Article

Change log

Authors

Martín-Buro, María Carmen  ORCID logo  https://orcid.org/0000-0003-0578-2825
Staresina, Bernhard P  ORCID logo  https://orcid.org/0000-0002-0558-9745

Abstract

Memories for past experiences can range from vague recognition to full-blown recall of associated details. Electroencephalography has shown that recall signals unfold a few hundred milliseconds after simple recognition, but has only provided limited insights into the underlying brain networks. Functional magnetic resonance imaging (fMRI) has revealed a "core recollection network" (CRN) centered on posterior parietal and medial temporal lobe regions, but the temporal dynamics of these regions during retrieval remain largely unknown. Here we used Magnetoencephalography in a memory paradigm assessing correct rejection (CR) of lures, item recognition (IR) and associative recall (AR) in human participants of both sexes. We found that power decreases in the alpha frequency band (10-12 Hz) systematically track different mnemonic outcomes in both time and space: Over left posterior sensors, alpha power decreased in a stepwise fashion from 500 ms onward, first from CR to IR and then from IR to AR. When projecting alpha power into source space, the CRN known from fMRI studies emerged, including posterior parietal cortex (PPC) and hippocampus. While PPC showed a monotonic change across conditions, hippocampal effects were specific to recall. These region-specific effects were corroborated by a separate fMRI dataset. Importantly, alpha power time courses revealed a temporal dissociation between item and associative memory in hippocampus and PPC, with earlier AR effects in hippocampus. Our data thus link engagement of the CRN to the temporal dynamics of episodic memory and highlight the role of alpha rhythms in revealing when and where different types of memories are retrieved.SIGNIFICANCE STATEMENT Our ability to remember ranges from the vague feeling of familiarity to vivid recollection of associated details. Scientific understanding of episodic memory thus far relied upon separate lines of research focusing on either temporal (via electroencephalography) or spatial (via functional magnetic resonance imaging) dimensions. However, both techniques have limitations that have hindered understanding of when and where memories are retrieved. Capitalizing on the enhanced temporal and spatial resolution of magnetoencephalography, we show that changes in alpha power reveal both when and where different types of memory are retrieved. Having access to the temporal and spatial characteristics of successful retrieval provided new insights into the cross-regional dynamics in the hippocampus and parietal cortex.

Description

Keywords

MEG, alpha, episodic memory, hippocampus, oscillations, parietal cortex, Adolescent, Adult, Alpha Rhythm, Association Learning, Brain Mapping, Female, Hippocampus, Humans, Magnetoencephalography, Male, Mental Recall, Nerve Net, Parietal Lobe, Psychomotor Performance, Recognition, Psychology, Young Adult

Journal Title

J Neurosci

Conference Name

Journal ISSN

0270-6474
1529-2401

Volume Title

40

Publisher

Society for Neuroscience
Sponsorship
Medical Research Council (MC_UU_00005/8)