TY - JOUR
T1 - Relationship between transcranial magnetic stimulation measures of intracortical inhibition and spectroscopy measures of GABA and glutamate+glutamine
AU - Tremblay, Sara
AU - Beaulé, Vincent
AU - Proulx, Sébastien
AU - de Beaumont, Louis
AU - Marjańska, Małgorzata
AU - Doyon, Julien
AU - Pascual-Leone, Alvaro
AU - Lassonde, Maryse
AU - Théoret, Hugo
PY - 2013
Y1 - 2013
N2 - 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.
AB - 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.
KW - Cortical silent period
KW - MEGA-PRESS
KW - Magnetic resonance spectroscopy
KW - Motor cortex
UR - http://www.scopus.com/inward/record.url?scp=84874616926&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84874616926&partnerID=8YFLogxK
U2 - 10.1152/jn.00704.2012
DO - 10.1152/jn.00704.2012
M3 - Article
C2 - 23221412
AN - SCOPUS:84874616926
SN - 0022-3077
VL - 109
SP - 1343
EP - 1349
JO - Journal of Neurophysiology
JF - Journal of Neurophysiology
IS - 5
ER -
