AUTHOR=Brix Maiken K., Ersland Lars, Hugdahl Kenneth, Grüner Renate, Posserud Maj-Britt, Hammar Åsa, Craven Alexander R., Noeske Ralph, Evans C. John, Walker Hanne B., Midtvedt Tore, Beyer Mona K. TITLE=“Brain MR spectroscopy in autism spectrum disorder—the GABA excitatory/inhibitory imbalance theory revisited” JOURNAL=Frontiers in Human Neuroscience VOLUME=9 YEAR=2015 URL=https://www.frontiersin.org/articles/10.3389/fnhum.2015.00365 DOI=10.3389/fnhum.2015.00365 ISSN=1662-5161 ABSTRACT=Magnetic resonance spectroscopy (MRS) from voxels placed in the left anterior cingulate cortex (ACC) was measured from 14 boys with Autism Spectrum Disorder (ASD) and 24 gender and age-matched typically developing (TD) control group. Our main aims were to compare the concentration of γ-aminobutyric acid (GABA) between the two groups, and to investigate the relationship between brain metabolites and autism symptom severity in the ASD group. We did find a significant negative correlation in the ASD group between Autism Spectrum Screening Questionnaire (ASSQ) and GABA+/Cr, which may imply that severity of symptoms in ASD is associated with differences in the level of GABA in the brain, supporting the excitatory/inhibitory (E/I) imbalance theory. However we did not find a significant difference between the two groups in GABA levels.