Researchers report that metabotropic glutamate receptor 5 (mGlu5) is less available across the brains of autistic adults, a finding published in The American Journal of Psychiatry that may clarify biological aspects of autism. James McPartland of Yale School of Medicine described the result as an important, previously unrecognised difference that has implications for intervention and for a more concrete understanding of autism.
The team combined positron emission tomography (PET), which maps receptor availability, with magnetic resonance imaging (MRI) to compare 16 autistic adults and 16 neurotypical adults. PET analyses showed lower brain‑wide mGlu5 in autistic participants, a result consistent with the leading idea that an imbalance between excitatory signalling (driven mainly by glutamate) and inhibitory signalling underlies many autism features.
Fifteen autistic participants had electroencephalogram (EEG) tests, and EEG measures of electrical brain activity correlated with lower mGlu5 levels. David Matuskey noted that PET can create a molecular map of the glutamate system, while Adam Naples said EEG might help show how these receptors contribute to ongoing brain activity.
The researchers caution about limits: PET is costly and involves radiation, and the study included only autistic adults who had average or above average cognitive abilities. It is unknown whether lower receptor availability causes autism or results from living with it. Yale investigators are developing lower‑radiation PET methods and plan studies in children, adolescents and broader participant groups to build a developmental picture.
Difficult words
- receptor — protein on cells that receives chemical signalsreceptors
- availability — degree to which something is present or usable
- glutamate — a brain chemical that helps send signals between neurons
- excitatory — increasing the chance that a neuron will activate
- inhibitory — reducing the chance that a neuron will activate
- positron emission tomography — a brain imaging method using radioactive tracer
- electroencephalogram — a test that records electrical brain activity
- neurotypical — not diagnosed with autism or developmental conditions
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Discussion questions
- How might the finding of lower mGlu5 availability influence future interventions for autism? Give one or two possible effects.
- What practical or ethical concerns arise from using PET, which involves radiation and cost, in studies with children?
- How could researchers design future studies to include a broader and more representative group of autistic participants?
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