Children’s Visual Engagement Is Heritable and Altered in Autism
BETHESDA, Md -- July 12, 2017 -- How children visually engage with others in social situations is a heritable behaviour that is altered in children with autism, according to a study published in the latest issue of Nature.
Reduced attention to other people’s eyes and faces is a behaviour associated with autism, and it is often used to screen for and help diagnose the disorder.
In the current study, researchers from Washington University, St. Louis, Missouri, and Emory University, Atlanta, Georgia, explored the potential genetic foundation of this behaviour, which can appear by the first 6 months of age and persist as children grow older.
“Research shows that autism likely has a genetic basis,” said Diana Bianchi, MD, National Institute of Child Health and Human Development (NICHD), part of the National Institutes of Health (NIH), Bethesda, Maryland. “Siblings of children diagnosed with autism and people with certain genetic mutations have a higher risk of developing the disorder, compared with the general population. Understanding how genes influence social behaviours will help researchers identify new or better ways to treat autism.”
The researchers conducted eye-tracking experiments in a group of 250 typically developing toddlers aged 18 to 24 months, including 82 identical twins (41 pairs), 84 non-identical twins (42 pairs), and 84 non-sibling children (42 randomised pairs). They also evaluated 88 non-twin children diagnosed with autism.
Each child watched videos that showed either an actress speaking directly to the viewer or scenes of children interacting in day-care. In all video frames, children could look at the onscreen characters’ eyes, mouth, body or surrounding objects. Special software captured how often the children looked at different regions, as well as the timing and direction of eye movements.
The team found that identical twins had synchronised visual patterns, compared with non-identical twins and non-sibling pairs. Identical twins tended to shift their eyes at the same times and in the same direction. They also were more likely to look at the subject’s eyes or mouth at the same moments.
Using intraclass correlation coefficient (ICC), which measures how well individuals within a group resemble each other (with a value of 1 marking perfect agreement), the researchers found that identical twins had an ICC of 0.91 for eye-looking and 0.86 for mouth-looking. On the other hand, non-identical twins had scores of 0.35 and 0.44, respectively, while non-sibling pairs had scores of 0.16 and 0.13.
To explore this concept further, the researchers evaluated children with autism and discovered that they looked at eye and mouth regions -- the most heritable visual traits -- much less, compared with the other groups of children.
With these findings, researchers can explore which genes are involved in social visual engagement, how these genes interact with a child’s environment to shape his/her social engagement, and how these genetic pathways are disrupted in neurodevelopmental disorders such as autism.
SOURCE: National Institutes of Health