GABA quantitation using MEGA-PRESS: Regional and hemispheric differences.

PURPOSE To measure in vivo brain gamma-aminobutyric acid (GABA) concentrations, and assess regional and hemispheric differences, using MR spectroscopy (1 H-MRS). MATERIALS AND METHODS GABA concentrations were measured bilaterally in the frontal cortex (FC), parietal cortex (PC), and occipital cortex (OC) of 21 healthy young subjects (age range 20-29 years) using 3 Tesla Philips scanner. A univariate general linear model analysis was carried out to assess the effect of region and hemisphere as well as their interaction on GABA concentrations while controlling for sex and gray matter differences. RESULTS Results indicated a significant regional dependence of GABA levels [F(2,89) = 11.725, P < 0.001, ηp2 = .209] with lower concentrations in the FC compared with both PC (P < 0.001) and OC (P < 0.001) regions. There was no significant hemispheric differences in GABA levels [F(1,89) = .172; P = 0.679; ηp2 = .002]. CONCLUSION This study reports the concentrations of GABA in the FC, PC, and OC brain regions of healthy young adults. GABA distribution exhibits hemispheric symmetry, but varies across regions; GABA levels in the FC are lower than those in the PC and OC. J. Magn. Reson. Imaging 2016;44:1619-1623.