Submitted on September 15, 2008
Revised on March 23, 2009
Accepted on March 24, 2009
The Neurochemical Effects of Theta Burst Stimulation as assessed by Magnetic Resonance Spectroscopy
Charlotte J. Stagg1*, Marzena Wylezinska2, Paul M. Matthews3, Heidi Johansen-Berg, Peter Jezzard4, John C. Rothwell5, and Sven Bestmann5
1 University of Oxford
2 Imperial College
3 Univ Oxford
4 John Radcliffe Hospital
5 Institute of Neurology
* To whom correspondence should be addressed. E-mail: cstagg{at}fmrib.ox.ac.uk.
Continuous Theta Burst Stimulation (cTBS) is a novel transcranial stimulation technique that causes significant inhibition of synaptic transmission for up to an hour when applied over the primary motor cortex (M1) in humans. Here we use Magnetic Resonance Spectroscopy to define mechanisms mediating this inhibition by non-invasively measuring local changes in the cortical concentrations of the GABA and glutamate/glutamine (Glx). cTBS to the left M1 led to an increase in GABA compared to stimulation at a control site without significant change in Glx. This direct evidence for increased GABAergic interneuronal activity is framed in terms of a new hypothesis regarding mechanisms underlying cTBS.
