Differences in white matter segments in autistic males, non-autistic siblings, and non-autistic participants: An intermediate phenotype approach.

Brain scans showed that autistic people and their non-autistic brothers have some similar brain differences in areas controlling thinking skills. However, only autistic people had changes in brain areas for understanding social situations. The non-autistic brothers showed stronger connections in some brain areas, possibly helping them cope. These findings suggest autism runs in families through shared brain patterns.

This neuroimaging study examined white matter differences in the brains of autistic males, their non-autistic siblings, and unrelated non-autistic participants. Researchers used advanced brain scanning to identify specific segments of neural pathways that differed between groups. They found that autistic individuals and their non-autistic siblings shared alterations in brain segments connected to executive functions, while segments related to social cognition and Theory of Mind were altered only in autistic participants. Non-autistic siblings showed compensatory increases in certain brain regions, suggesting adaptive changes.

These shared differences between autistic individuals and siblings may represent 'intermediate phenotypes' - biological markers that bridge genetics and autism symptoms, potentially advancing understanding of autism's neurobiological foundations.

Findings suggest potential neuroimaging biomarkers for autism and familial risk assessment. The identification of compensatory brain changes in siblings may inform understanding of protective factors and guide future research into brain adaptation mechanisms in autism spectrum conditions.

Sample size not reported, study design unclear, male-only sample limits generalizability. Abstract lacks details on methodology, statistical analyses, and effect sizes. Causal relationships between brain differences and autism traits cannot be established.

White matter is the neural pathway that connects neurons in different brain regions. Although research has shown white matter differences between autistic and non-autistic people, little is known about the properties of white matter in non-autistic siblings. In addition, past studies often focused on the whole neural tracts; it is unclear where differences exist in specific segments of the tracts. This study identified neural segments that differed between autistic people, their non-autistic siblings, and the age- and non-autistic people.

We found altered segments within the tracts connected to anterior brain regions corresponding to several higher cognitive functions (e.g. executive functions) in autistic people and non-autistic siblings. Segments connecting to regions for social cognition and Theory of Mind were altered only in autistic people, explaining a large portion of autistic traits and may serve as neuroimaging markers. Segments within the tracts associated with fewer autistic traits or connecting brain regions for diverse highly integrated functions showed compensatory increases in the microstructural properties in non-autistic siblings. Our findings suggest that differential white matter segments that are shared between autistic people and non-autistic siblings may serve as potential "intermediate phenotypes"-biological or neuropsychological characteristics in the causal link between genetics and symptoms-of autism.

These findings shed light on a promising neuroimaging model to refine the intermediate phenotype of autism which may facilitate further identification of the genetic and biological bases of autism. Future research exploring links between compensatory segments and neurocognitive strengths in non-autistic siblings may help understand brain adaptation to autism.