Exploring the relationship between cortical GABA concentrations, auditory gamma-band responses and development in ASD: Evidence for an altered maturational trajectory in ASD.
Russell G Port, William Gaetz, Luke Bloy and 6 others
PMID 27696740WHAT IT FOUND
In people with autism, brain GABA and an auditory gamma response were lower than controls.
In typically developing children, GABA tracked the response; in autistic children it did not. This is a brain measurement study, not a treatment result.
Key findings
01Compared with typically developing participants, the ASD group had lower relative cortical GABA+ (TD=0.31±0.01, ASD=0.28±0.01) and lower auditory gamma-band coherence (TD=0.067±0.003, ASD=0.058±0.003).
02Across the whole analysed sample, higher GABA+ was associated with greater gamma-band coherence (slope beta=0.126, t(55)=2.73, p<0.01).
03In TD children/adolescents, GABA+ was associated with gamma-band coherence (skipped Pearson r=0.900), but no association was evident in ASD children/adolescents.
STILL TO COME
How it was doneWhat they found
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What it does not show
The final analysis had 57 participants, and the child/adult subgroups were small: 10 TD children/adolescents, 16 ASD children/adolescents, 17 TD adults and 14 ASD adults; the authors say these groups may be underpowered. Seventeen of 74 participants were removed for poor scan quality, including 12 with ASD, so the analysed sample is not the full recruited sample. The whole sample and adult groups differed in age; age-matching adults left only 5 TD and 6 ASD adults, too small for robust effects. Two TD participants were prescribed non-psychotropic medication, and 15 individuals with ASD were prescribed medications or took dietary supplements. The study measured relative GABA+ in a left temporal voxel and did not measure glutamate, so it cannot show a full excitatory/inhibitory imbalance or separate metabolic from neurotransmitter GABA. The study did not test treatment or clinical behavioural outcomes.
The easy way to misread this
Do not read these brain measures as evidence that GABA imbalance causes autism or that GABA-based drugs will help. The study did not test treatment, and the authors say it remains to be established whether these measures are causal for behavioral changes.