Fig. 1

Magnetic resonance spectroscopy voxel placement and data processing. A This schematic diagram demonstrates the voxel placement in the periaqueductal gray (PAG) (a) and dentate nucleus (DN) (b). The red lines represent the region of interest. B The processed gamma-aminobutyric acid (GABA)-edited difference spectrum (a) before frequency and phase correction (red) and (b) after (blue). The residual water signal is plotted against time, providing qualitative information about the stability of the experiment The creatine (Cr) signal over the duration of the experiment is shown (c). The y-axis represents the frequency (in ppm) of the Cr signal. The modeling of the GABA signal is shown (d). The GABA-edited spectrum is shown in blue. The red represents the model of best fit. The residual between these two is shown in black. Modeling of the signal against which GABA is quantified is shown (e). Data are shown in blue. Models are shown in red. Residuals are shown in black. L, left; R, right