Figure 6.

NAA, tCr, Glx and Glu ACC concentrations during rest (no pain perception) and pain onset for each volunteer (n = 15). Exploratory sex-based analysis showed a large effect for change in glutamate at pain onset in females (Cohen’s d = 0.88, CI − 0.43 to 2.21, n = 7), compared with a medium sized effect for males (Cohen’s d = 0.60 CI − 0.57 to 1.73, n = 8). Changes in Glx at pain onset were medium sized for both men (Cohen’s d = 0.65 CI − 0.53 to 1.83) and women (Cohen’s d = 0.58 CI − 0.69 to 1.87). There was no difference in pain rating at onset between men and women (t = − 0.24, p-value = 0.80 CI − 1.2 to 0.9).