Differences between Autism spectrum disorders and attention-deficit/hyperactivity disorder in brain function: A...

The clinical distinction between ASD and ADHD poses significant diagnostic challenges due to their symptomatic similarities. To address this issue, we systematically examined functional brain differences between these disorders.

By combining amplitude of low-frequency fluctuations (ALFF) and regional homogeneity (ReHo) resting-state fMRI metrics, this study provides a more robust neurofunctional characterization of ASD and ADHD. Using resting-state fMRI, we compared ALFF and ReHo among four groups: 28 ASD-only participants, 29 typically developing controls matched to ASD participants (TD(ASD)), 28 ADHD-only participants, 30 typically developing controls matched to ADHD participants (TD(ADHD)). These analyses quantified region-specific neural activity intensity and local synchronization to identify disorder-specific functional patterns.

Compared to TD(ASD) controls, the ASD group exhibited significantly elevated ALFF and ReHo in the anterior cingulate gyrus (ACG) and right precentral gyrus (PreCG) (p < 0.05, GRF-corrected). In contrast, no significant differences were observed between ADHD and TD(ADHD) groups. Direct ASD-ADHD comparisons revealed: Increased ALFF in the right PreCG and decreased ALFF in the left fusiform gyrus (FG); Elevated ReHo in the right middle occipital gyrus (MOG) in ASD (p < 0.05, GRF-corrected).

The distinct ALFF and ReHo patterns observed between ASD and ADHD provide compelling neurobiological evidence for their divergent neural mechanisms. These disorder-specific functional signatures, particularly in the anterior cingulate and occipito-frontal circuits, may guide future neuromodulation research and eventually contribute to refining differential diagnostic frameworks in clinical practice.