Task-based changes in proton MR spectroscopy signal during configural working memory in human medial temporal lobe

Kyle F Shattuck; John W VanMeter

doi:10.1002/jmri.25816

Task-based changes in proton MR spectroscopy signal during configural working memory in human medial temporal lobe

J Magn Reson Imaging. 2018 Mar;47(3):682-691. doi: 10.1002/jmri.25816. Epub 2017 Jul 12.

Authors

Kyle F Shattuck^{1

2

3}, John W VanMeter^{2

3}

Affiliations

¹ Department of Neuroscience, Georgetown University Medical Center, Washington, D.C., USA.
² Department of Neurology, Georgetown University Medical Center, Washington, D.C., USA.
³ Center for Functional and Molecular Imaging, Georgetown University Medical Center, Washington, D.C., USA.

Abstract

Purpose: To detect local cholinergic changes in human medial temporal lobe during configural working memory performance.

Materials and methods: Proton magnetic resonance spectroscopy (¹ H-MRS) measurements were acquired at 3T from a 2 × 2 × 3 cm voxel in right medial temporal lobe from 36 subjects during performance of a configural visual working memory task (cWMT). In order to compensate for expected task-based blood oxygenation level-dependent (BOLD) T₂ * effects, resonance signal changes of unbound choline-containing metabolites (Cho) were referenced to an internal standard of creatine + phosphocreatine metabolites (Cre) and compared between four task blocks: rest, memorization, active memory maintenance, and recognition. An unannounced memory retention test was conducted in 21 subjects. Quality assurance analyses examined task-based Cho and Cre individually as well as referenced to resonance signal from N-acetylaspartate (NAA).

Results: Increases from a resting baseline in the Cho/Cre ratio were observed during 60-second blocks of active memory maintenance across the group (P = 0.0042). Behavioral accuracy during task performance correlated with memory retention (r = 0.48, P = 0.027). Quality assurance measures showed task-based changes in Cre resonance signal both individually (P = 0.00099) and when utilized as a noncholinergic internal reference (NAA/Cre, P = 0.00079).

Conclusion: Increases in human medial temporal lobe ¹ H-MRS Cho/Cre ratio occur during the maintenance of configural working memory information. However, interpretation of these results as driven by cholinergic activity cannot be assumed, as NAA, a noncholinergic metabolite, shows similar results when utilizing Cre as a reference. Caution is advised when considering Cre as an internal standard for task-based ¹ H-MRS measurements.

Level of evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:682-691.

Keywords: acetylcholine; choline; creatine; magnetic resonance spectroscopy; medial temporal lobe; working memory.

Publication types

Research Support, N.I.H., Extramural

MeSH terms

Adolescent
Adult
Female
Humans
Male
Memory, Short-Term / physiology*
Proton Magnetic Resonance Spectroscopy / methods*
Task Performance and Analysis
Temporal Lobe / diagnostic imaging*
Temporal Lobe / physiology*
Young Adult

Abstract

Publication types

MeSH terms

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