Decoding the brain's excitatory-inhibitory metabolite balance in relation to sensory responsivity and autistic traits.

Researchers studied brain chemistry in 92 adults without autism to see how brain balance relates to autism-like traits and sensory sensitivities. They found that people with more autism-like traits had different brain chemical balances, especially in the front part of the brain. This suggests that similar brain differences might exist in everyone, not just people diagnosed with autism.

This neuroimaging study examined brain excitatory-inhibitory (E-I) balance in 92 neurotypical adults to understand its relationship with sensory responsivity and autistic traits. Researchers measured glutamate/glutamine to GABA ratios (Glx/GABA) across sensory-related brain regions using magnetic resonance spectroscopy. Results showed that individuals with higher self-reported autistic traits had elevated Glx/GABA ratios and stronger associations with sensory responsivity. The prefrontal cortex showed the strongest associations between E-I imbalance and both autistic traits and sensory processing differences.

Clustering analyses indicated that the metabolite ratio was more behaviorally relevant than individual neurotransmitter concentrations alone. These findings suggest that E-I imbalance may underlie sensory and social processing differences even in non-clinical populations, providing insights into the neurobiological mechanisms of autism-related traits across the broader population spectrum.

Results suggest E-I imbalance may be a dimensional neurobiological marker relevant across the autism spectrum. Prefrontal E-I balance could potentially serve as a biomarker for sensory processing differences. Findings support dimensional models of autism and may inform future targeted interventions.

Study limited to neurotypical adults, so findings may not generalize to clinical autism populations. Cross-sectional design prevents causal conclusions. Self-reported measures of autistic traits may introduce bias. No comparison with diagnosed autistic individuals to validate neurobiological differences.

Brain excitatory-inhibitory (E-I) balance plays a fundamental role in sensory and social processing. Alterations in E-I neurotransmitter systems-commonly indexed by the glutamate and glutamine (Glx)/GABA ratio-have been implicated in various neurodevelopmental conditions, including autism spectrum disorder (ASD). However, how individual differences in E-I balance relate to sensory responsivity and autism-spectrum-related traits in neurotypical populations remains poorly understood. In this study, we evaluated E-I balance across sensory-related brain regions in 92 neurotypical participants to explore its association with sensory responsivity and autistic traits.

Our findings revealed that individuals with higher levels of self-reported autistic traits also exhibited stronger associations with sensory responsivity and higher Glx/GABA ratios. In cross-correlation analyses, the Glx/GABA ratio was significantly associated with both autistic traits and sensory responsivity, whereas Glx alone showed fewer associations. Clustering analyses further grouped autistic traits with the Glx/GABA ratio, rather than with the individual metabolite concentrations, suggesting that the ratio may be more behaviorally relevant than either metabolite alone. Moreover, the prefrontal Glx/GABA ratio demonstrated stronger associations with both autistic traits and sensory responsivity compared to other brain regions, a finding further supported by hierarchical moderation and mediation analyses.

Overall, these results suggest that individual variability in regional E-I balance may be meaningfully related to sensory and social-affective traits, even within non-clinical populations. These findings may offer insights into the broader neurobiological mechanisms underlying sensory-affective processing across the general population spectrum.