Social visual engagement in autistic children is heritable, atypical

In children with autism, visual engagement with others in social situations is not only atypical but genetically controlled as well, according to results published online in the journal Nature.

In this study, researchers from Washington University, St. Louis, MO, and Emory University, Atlanta, GA sought to determine the potential genetic foundation of reduced attention to other people’s eyes and faces, which may appear by the first 6 months of life in autistic infants, and persists as the child grows.

“Research shows that autism likely has a genetic basis. Siblings of children diagnosed with autism and people with certain genetic mutations have a higher risk of developing the disorder, compared to the general population,” said Diana Bianchi, MD, director, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), which provided funding for the study. “Understanding how genes influence social behaviors will help researchers identify new or better ways to treat autism.”

In 250 typical toddles aged 18 to 24 months, researchers performed eye-tracking experiments. Subjects included 41 pairs of identical twins, 42 pairs of non-identical twins, 42 randomized pairs of non-siblings, and 88 non-twin children with autism.

The children watched videos showing either an actress speaking directly to the viewer or scenes of children interacting in daycare. In all video frames, children could look onscreen at the characters’ eyes, mouth, body, or surrounding objects. Using special software, researchers captured how frequently the children looked at different regions, the timing, and the direction of their eye movements.

They found that identical twins had synchronized visual patterns compared with non-identical twins and non-sibling pairs, and had a tendency to shift their eyes at the same times and in the same directions. Identical twins were also more likely to look at the subjects’ eyes or mouths at the same moments.

Upon analyzing intraclass correlation coefficient (ICC) to measure how well individuals within each group resemble each other (1=perfect agreement), they found an ICC of 0.91 in identical twins for eye-looking, and 0.86 for mouth-looking, compared with 0.35 and 0.44, respectively in non-identical twins, and 0.16 and 0.13 in non-sibling pairs.

“By comparing identical twins who share the same genes to non-identical twins and randomly paired children who do not share the same genes, the study is one of the first to show that social visual behaviors are under genetic control,” said Lisa Gilotty, PhD, chief, NIMH’s Research Program on Autism Spectrum Disorders.

Finally, researchers found that children with autism looked at eye and mouth regions much less compared with these other groups (χ²=64.03, P < 0.0001).

Based on these findings, researchers will study which genes may be involved in social visual engagement, how they interact with a child’s environment to shape social engagement, and how genetic pathways are disrupted in autism and other neurodevelopmental disorders.

This study was funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) and the National Institute of Mental Health (NIMH), with additional funding provided by the Marcus Foundation, the Whitehead Foundation, and the Georgia Research Alliance.