Concentrations of Cortical GABA and Glutamate in Young Adults With Autism Spectrum Disorder.
Tamar Kolodny, Michael-Paul Schallmo, Jennifer Gerdts and 3 others
PMID 32297709WHAT IT FOUND
Young adults with autism had typical brain chemical levels linked to excitation and inhibition across visual, auditory and motor regions.
These levels did not relate to visual sensitivity or overall autism severity, so this study does not support an excitation-inhibition imbalance in adults.
Key findings
01GABA+ and Glx concentrations did not differ between young adults with autism and neurotypical adults in any brain region measured.
02Analyses provided moderate evidence for no group difference in most regions.
03GABA+ and Glx levels were not significantly correlated with visual sensitivity or overall autism symptom severity.
STILL TO COME
How it was doneWhat they foundWhat it means for OTs
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What it does not show
The study included only young adults aged 18 to 30 with IQ at least 75, so it does not show what happens in children, adolescents, or adults with lower IQ. It measured total GABA+ and Glx, not synaptic neurotransmitter activity. GABA+ includes coedited macromolecules, and Glx combines glutamate, glutamine and glutathione. The spatial resolution was limited to large voxels, so small region-specific differences could be missed. Several scans were missing or excluded for artefacts, and the medication subgroup analyses had low power. Participants watched a movie during scanning, which the authors note could add noise, although they judged the benefit for compliance greater. The study was not designed to test a therapy or to determine whether brain chemistry causes ASD symptoms.
Declared interests
The authors declared no conflict of interest. The paper is listed as supported by NIH extramural research funding.
The easy way to misread this
Do not conclude that GABA and glutamate neurotransmission are normal in autism. This study only measured total GABA+ and Glx by MRS in sensory and sensorimotor cortex in young adults, and the authors say this cannot rule out underlying neurotransmitter differences.