Brains of autistic children grow much slower than their healthy peers

Researchers at UCLA have, for the first time, found that the connections between brain regions that are important for language and social skills, grow much more slowly in boys with autism than in non-autistic children – a possible explanation for why autistic children act and think differently than their peers.

They found aberrant growth rates in areas of the brain implicated in the social impairment, communication deficits and repetitive behaviours that characterize autism.

Normally, as children grow into teenagers, the brain undergoes major changes.

This highly dynamic process depends on the creation of new connections, called white matter, and the elimination, or “pruning,” of unused brain cells, called gray matter.

As a result, our brains work out the ideal and most efficient ways to understand and respond to the world around us.

Although most children with autism are diagnosed before they are 3 years old, this new study suggested that delays in brain development continue into adolescence.

“Because the brain of a child with autism develops more slowly during this critical period of life, these children may have an especially difficult time struggling to establish personal identity, develop social interactions and refine emotional skills,” said Xue Hua, a UCLA postdoctoral researcher and first author of the study.

“This new knowledge may help to explain some of the symptoms of autism and could improve future treatment options,” she stated.

The researchers used a type of brain-imaging scan called a T1-weighted MRI, which can map structural changes during brain development.

To study how the brains of boys with autism changed over time, they scanned 13 boys (age 6 to 14) diagnosed with autism and a control group of seven non-autistic boys on two separate occasions.

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They discovered that the white-matter connections between those brain regions that are important for language and social skills were growing much slower in the boys with autism.

Besides this defect they also found a second anomaly: In two areas of the brain — the putamen, which is involved in learning, and the anterior cingulate, which helps regulate both cognitive and emotional processing — unused cells were not properly pruned away.

“Together, this creates unusual brain circuits, with cells that are overly connected to their close neighbours and under-connected to important cells further away, making it difficult for the brain to process information in a normal way,” Hua said.

“The brain regions where growth rates were found to be the most altered were associated with the problems autistic children most often struggle with — social impairment, communication deficits and repetitive behaviour,” she added.

Senior author Jennifer G. Levitt, a professor of psychiatry at the Semel Institute for Neuroscience and Human Behaviour at UCLA said, “This study provides a new understanding of how the brains of children with autism are growing and developing in a unique way.”

The study was reported in the current online edition of the journal Human Brain Mapping.

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