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Comparing GABA-­dependent physiological measures of inhibition with proton magnetic resonance spectroscopy measurement of GABA using ultra-­high-­field MRI

Dyke, Katherine; Pépés, Sophia E.; Chen, Chen; Kim, Soyoung; Sigurdsson, Hilmar P.; Draper, Amelia; Husain, Masud; Nachev, Parashkev; Gowland, Penelope A.; Morris, Peter G.; Jackson, Stephen R.

Authors

Katherine Dyke

Sophia E. Pépés

Chen Chen

Soyoung Kim

Hilmar P. Sigurdsson

Masud Husain

Parashkev Nachev

Penelope A. Gowland

Peter G. Morris

Stephen R. Jackson



Abstract

Imbalances in glutamatergic (excitatory) and GABA (inhibitory) signalling within key brain networks are thought to underlie many brain and mental health disorders, and for this reason there is considerable interest in investigating how individual variability in localised concentrations of these molecules relate to brain disorders. Magnetic resonance spectroscopy (MRS) provides a reliable means of measuring, in vivo, concentrations of neurometabolites such as GABA, glutamate and glutamine that can be correlated with brain function and dysfunction. However, an issue of much debate is whether the GABA observed and measured using MRS represents the entire pool of GABA available for measurement (i.e., metabolic, intracellular, and extracellular) or is instead limited to only some portion of it. GABA function can also be investigated indirectly in humans through the use of non-invasive transcranial magnetic stimulation (TMS) techniques that can be used to measure cortical excitability and GABA-mediated physiological inhibition. To investigate this issue further we collected in a single session both types of measurement, i.e., TMS measures of cortical excitability and physiological inhibition and ultra-high-field (7 Tesla) MRS measures of GABA, glutamate and glutamine, from the left sensorimotor cortex of the same group of right-handed individuals. We found that TMS and MRS measures were largely uncorrelated with one another, save for the plateau of the TMS IO curve that was negatively correlated with MRS-Glutamate (Glu) and intra-cortical facilitation (10ms ISI) that was positively associated with MRS-Glutamate concentration. These findings are consistent with the view that the GABA concentrations measured using MRS largely represent pools of GABA that are linked to tonic rather than phasic inhibition and thus contribute to the inhibitory tone of a brain area rather than GABAergic synaptic transmission.

Journal Article Type Article
Publication Date May 15, 2017
Journal NeuroImage
Print ISSN 1053-8119
Electronic ISSN 1095-9572
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 152
Pages 360-370
APA6 Citation Dyke, K., Pépés, S. E., Chen, C., Kim, S., Sigurdsson, H. P., Draper, A., …Jackson, S. R. (2017). Comparing GABA-­dependent physiological measures of inhibition with proton magnetic resonance spectroscopy measurement of GABA using ultra-­high-­field MRI. NeuroImage, 152, 360-370. https://doi.org/10.1016/j.neuroimage.2017.03.011
DOI https://doi.org/10.1016/j.neuroimage.2017.03.011
Publisher URL http://www.sciencedirect.com/science/article/pii/S1053811917302197
Copyright Statement Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by/4.0
Additional Information This article is maintained by: Elsevier; Article Title: Comparing GABA-dependent physiological measures of inhibition with proton magnetic resonance spectroscopy measurement of GABA using ultra-high-field MRI; Journal Title: NeuroImage; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.neuroimage.2017.03.011; Content Type: article; Copyright: © 2017 The Authors. Published by Elsevier Inc.

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Copyright Statement
Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by/4.0





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