Journal of International Psychiatry

Autism is a multi-dimensional spectrum disorder that have substantial phenotypic overlap. Recent theoretical accounts have proposed the imbalance of excitation and inhibition as a possible mechanistic, network level hypothesis underlying neural and behavioral dysfunction across autism spectrum disorder (ASD). The global glutamatergic and γ-Aminobutyric acidergic (GABAergic) signalling are core to the understanding of excitation and inhibition imbalance. In the reviw, the neurochemistry of global circuits in paediatric and adult ASD, as described in 25 studies, is outlined from the perspective of proton magnetic resonance spectroscopy (1H-MRS). Despite the methodological inconsistencies between studies, two observations stand out that form possible hypotheses for future studies. Firstly, a possible increase in Glx (combination of Glu, glutamine and GABA) in the striatum across ASD. Secondly, an increased Glx signal in the anterior cingulate cortex in paediatric ASD but a lower Glx signal in adult ASD. This suggests neurodevelopmental changes in fronto-striatal glutamatergic circuits across the lifespan. Future studies should incorporate more homogeneous samples, perform MRS at field strengths of at least 3T and provide much more precise and standardized information on methods.

Autism spectrum disorder; Proton magnetic resonance spectroscopy; The imbalance of excitation and inhibition