Functional Changes in GABA and Glutamate during Motor Learning

Functional magnetic resonance spectroscopy (fMRS) of GABA at 3 T poses additional challenges compared with fMRS of other metabolites because of the difficulties of measuring GABA levels; GABA is present in the brain at relatively low concentrations, and its signal is overlapped by higher concentration metabolites. Using 7 T fMRS, GABA levels have been shown to decrease specifically during motor learning (and not during a con-trol task). Though the use of 7 T is appealing, access is limited. For GABA fMRS to be widely accessible, it is essential to develop this method at 3 T. Nine healthy right-handed participants completed a motor learning and a control button-pressing task. fMRS data were acquired from the left sensorimotor cortex during the task using a continuous GABA-edited MEGA-PRESS acquisition at 3 T. We found no significant changes in GABA1/tCr, Glx/tCr, or Glu/tCr levels in either task; however, we show a positive relationship between motor learning and glutamate levels both at rest and at the start of the task. Though further refinement and validation of this method is needed, this study represents a further step in using fMRS at 3 T to probe GABA levels in both healthy cognition and clinical disorders.Significance StatementGABA is the major inhibitory neurotransmitter in the brain and plays a key role in motor learning. Functional, noninvasive measures of GABA in humans in vivo is desirable; however, there has been little development of GABA functional magnetic resonance spectroscopy (fMRS) because of the challenges of measuring GABA. This study investigates the use of GABA-editing (Mescher-Garwood point resolved spectroscopy, MEGA-PRESS) at 3 T to acquire functional measures of GABA and glutamate levels during a behavior task. Our study highlights some of the issues facing the fMRS literature and can be used to guide future studies investigating GABA and glutamate levels simultaneously during motor learning.