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Brain Activity Differs in Infant Siblings of Children with Autism

A new study shows that infants as young as 6 months who are siblings of children with autism have different patterns of brain activity compared to infants who do not have a sibling with autism. These differences in brain activity were present even in infant siblings who did not go on to develop autism. Thus, they may reflect genetic differences that are shared by children with autism and their younger siblings.

The study was published in the journal PLoS One and was supported in part by a grant from Autism Speaks. Charles Nelson III, Ph.D., research director of the division of developmental medicine at Boston Children’s Hospital and professor of pediatrics at Harvard Medical School, led the research team.

Dr. Nelson and colleagues recruited 57 low-risk infants and 65 high-risk infants to take part in the study. High-risk infants had an older sibling with an autism spectrum disorder (ASD). The researchers used electroencephalograms (EEGs), which record the electrical activity along the scalp, to measure the babies’ brain activity at 6, 9, 12, 18 and 24 months of age. They monitored six different types of brain wave frequencies, including those reflecting level of alertness, processing and integration of information. They also examined how brain activity changed over time as the children aged. This is the first study to look at different wavelength frequencies across different periods of development in high-risk infants.

The study found that at 6 months of age, high-risk infants showed a pattern of brain activity that was more similar to that found in younger infants. In other words, their patterns of brain activity appeared delayed. However, by 24 months of age, the high risk infants had “caught up” and no longer differed from the low risk infants. This early delay in patterns of brain activity followed by a normalization of brain activity by age 2 may reflect genetic differences.   

“High risk infants, regardless of whether they are ultimately diagnosed with autism or not, show differences in EEG over the first 2 years of life,” says Dr. Nelson.

Past research has shown that persons with ASD have different brain activity than typically developed individuals. But scientists still do not understand whether these differences remain constant or change over time, or when they first emerge in development. The results of this study begin to answer those questions. The new research suggests that brain development of children at high risk for autism begins to diverge within the first six months of life. 

”These findings suggest that siblings of children with autism show subtle differences in their patterns of brain activity early in life, but they apparently resolve by the time they are toddlers,”  says Autism Speaks Chief Science Officer Geri Dawson, Ph. D. “Although these early differences do not appear to be predictive of an autism diagnosis, they may help explain milder kinds of developmental delays that siblings of children with autism sometime show."

Autism Speak recently launched its “Move the Needle” initiative, a collaboration of researchers, stakeholders and government agencies dedicated to lowering the age of autism detection and improving the quality of available interventions. For more information on high-risk younger siblings of children with autism, see our Baby Siblings Research Consortium Annual Report. This research would not be possible without the support of our families, donors and volunteers. We invite you to explore related Autism Speaks-funded studies using out website’s Grant Search