A 3T MR scanner (Siemens) was used with a 32-channel head matrix coil in the Brown University MRI Research Facility. A high-resolution T1-weighted anatomical brain structure images were obtained using a magnetization-prepared rapid gradient echo (MPRAGE; 256 slices, voxel size = 1×1×1 mm3, 0 mm slice gap, TR=2530 ms, TE=1.64 ms, flip angle=7 degrees, FoV=256 mm, matrix size =256×256, bandwidth=651 Hz/pixel) sequence. The GABA scans were conducted using a MEGA-PRESS sequence55 (link)-57 (link) (TR=1500 ms, TE=68 ms, number of average=256, scan time=774 sec) with double-banded pulses which were used to simultaneously suppress water signal and edit the γ-CH2 resonance of GABA at 3 ppm. We obtained the final spectra by subtracting the signals from alternate scans with the selective double-banded pulse applied at 4.7 and 7.5 ppm (‘Edit Off’) and the selective double-banded pulse applied at 1.9 and 4.7 ppm (‘Edit On’).
The glutamate scans were conducted using the PRESS sequence58 (link),59 (link) (TR=3000 ms, TE=30 ms, number of average=128, scan time=384 sec). A variable pulse power and optimized relaxation delays (VAPOR) technique60 (link) was used in both sequences to achieve water suppression.