GABA and Glx predict EEG responses of visual sensitivity in autism.

Researchers studied brain chemistry and visual processing in 20 autistic adults and 16 non-autistic adults. They found no differences between the groups in brain chemicals or how well they detected visual patterns. However, in both groups, people with certain brain chemical balances were better at detecting some visual features but worse at detecting others. This suggests that brain chemistry affects visual sensitivity in similar ways for both autistic and non-autistic people.

This study investigated the relationship between brain chemistry and visual sensitivity in autism by combining EEG and magnetic resonance spectroscopy data from 20 autistic adults and 16 neurotypical controls. Researchers measured GABA and glutamate (Glx) concentrations in the visual cortex and neural detection thresholds for visual stimuli. No group differences were found between autistic and neurotypical participants in either brain chemistry or neural detection thresholds. However, across all participants, lower Glx/GABA ratios were associated with better contrast detection and poorer spatial frequency detection.

These correlations were significant within both groups separately, suggesting that the balance between excitatory and inhibitory neurotransmitters regulates visual sensitivity regardless of autism diagnosis.

Results suggest that visual sensitivity interventions should consider individual neurochemical profiles rather than assuming uniform differences based on autism diagnosis. The findings may inform personalized approaches to sensory interventions and highlight the importance of measuring individual differences in visual processing.

Small sample size (36 total participants) limits generalizability. Cross-sectional design prevents causal inferences. Study focused only on occipital cortex and may not reflect broader brain differences. Limited to adults, so findings may not apply to children.

The mechanisms underlying atypical sensory processing in autism remain to be elucidated, but research points toward a role of the glutamatergic/GABAergic balance. To investigate the potential relationships between visual sensitivity and its molecular correlates in autism, we combined data from electroencephalography (EEG) and magnetic resonance spectroscopy (MRS) studies. Twenty autistic adults and sixteen neurotypical adults (NT) participated in both an EEG study assessing visual sensitivity (Sapey-Triomphe et al., Autism Research, 2023) and in an MRS study measuring Glx and GABA+ concentrations in the occipital cortex (Sapey-Triomphe et al., Molecular Autism, 2021). These studies revealed no group differences in neural detection thresholds or in Glx/GABA levels in the occipital cortex.

Neural detection thresholds for contrast and spatial frequency (SF) were determined using fast periodic visual stimulations and neural frequency tagging. In the present study, Glx/GABA+ concentrations in the occipital cortex and neural detection thresholds did not differ between groups. Interestingly, lower Glx/GABA+ ratios were associated with lower contrast detection thresholds and higher SF detection thresholds. These correlations were also significant within the neurotypical and autistic groups.

This report suggests that the Glx/GABA balance regulates visual detection thresholds across individuals. In both autistic and NTs, lower Glx/GABA ratios in the occipital cortex allow for better detection of visual inputs at the neural level. This study sheds light on the neurochemical underpinnings of visual sensitivity in autism and warrants further investigation.