Relationship between transcranial magnetic stimulation measures of intracortical inhibition and spectroscopy measures of GABA and glutamate+glutamine
Author(s) -
Sara Tremblay,
Vincent Beaulé,
Sébastien Proulx,
Louis De Beaumont,
Małgorzata Marjańska,
Julien Doyon,
Álvaro PascualLeone,
Maryse Lassonde,
Hugo Théoret
Publication year - 2012
Publication title -
journal of neurophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 245
eISSN - 1522-1598
pISSN - 0022-3077
DOI - 10.1152/jn.00704.2012
Subject(s) - transcranial magnetic stimulation , glutamate receptor , neurochemical , neuroscience , inhibitory postsynaptic potential , neurotransmitter , gamma aminobutyric acid , chemistry , glutamine , stimulation , receptor , psychology , medicine , endocrinology , central nervous system , biology , biochemistry , amino acid
Transcranial magnetic stimulation (TMS) can provide an index of intracortical excitability/inhibition balance. However, the neurochemical substrate of these measures remains unclear. Pharmacological studies suggest the involvement of GABAA and GABAB receptors in TMS protocols aimed at measuring intracortical inhibition, but this link remains inferential. Proton magnetic resonance spectroscopy ((1)H-MRS) permits measurement of GABA and glutamate + glutamine (Glx) concentrations in the human brain and might help in the direct empirical assessment of the relationship between TMS inhibitory measures and neurotransmitter concentrations. In the present study, MRS-derived relative concentrations of GABA and Glx measured in the left M1 of healthy participants were correlated with TMS measures of intracortical inhibition. Glx levels were found to correlate positively with TMS-induced silent period duration, whereas no correlation was found between GABA concentration and TMS measures. The present data demonstrate that specific TMS measures of intracortical inhibition are linked to shifts in cortical Glx, rather than GABA neurotransmitter levels. Glutamate might specifically interact with GABAB receptors, where higher MRS-derived Glx concentrations seem to be linked to higher levels of receptor activity.
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