Levels of γ-aminobutyric acid (GABA) within the right anterior insula (A), anterior cingulate (B), right posterior insula (C), and occipital cortex (D) of individual patients with fibromyalgia (FM) compared with healthy controls (HC). FM patients have reduced concentrations of GABA in the right anterior insula, with a trend toward elevated concentrations of GABA in the anterior cingulate, as compared to healthy controls. There are no between-group differences in the right posterior insula or occipital cortex. Circles represent individual subjects; horizontal bars indicate the mean. AIU = arbitrary institutional units.