Relationship between transcranial magnetic stimulation measures of intracortical inhibition and spectroscopy measures of GABA and glutamate+glutamine

Sara Tremblay, Vincent Beaulé, Sébastien Proulx, Louis de Beaumont, Małgorzata Marjańska, Julien Doyon, Alvaro Pascual-Leone, Maryse Lassonde, Hugo Théoret

Research output: Contribution to journalArticle

59 Scopus citations

Abstract

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 (1H-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.

Original languageEnglish (US)
Pages (from-to)1343-1349
Number of pages7
JournalJournal of neurophysiology
Volume109
Issue number5
DOIs
StatePublished - 2013

Keywords

  • Cortical silent period
  • MEGA-PRESS
  • Magnetic resonance spectroscopy
  • Motor cortex

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