A collaborative U.S. research team has concluded that autism begins during pregnancy. The scientists found that during development of the brain, the cortical layers of autistic children are disrupted.
They analyzed 25 genes in tissue from deceased children, some with autism and some who showed no evidence of the disorder. Among the genes were some that are biomarkers for types of brain cells in various layers of the cortex, genes known to have a role in autism, and a few control genes, according to ScienceDaily. The researchers represented the University of California, San Diego (UC San Diego) School of Medicine and the Allen Institute for Brain Science and published their findings online in the New England Journal of Medicine.
The Autism Center of Excellence at UC San Diego defines autism as a developmental disorder characterized by an abnormal development and functioning of the brain. Patients typically show repetitive or restricted behavioral and interest patterns.
When Leo Kanner identified the condition now known as Autism Spectrum Disorder (ASD) in 1943, the identified incidence of the condition was 1 in every 2,000 children. Today, it is more common than childhood diabetes. Experts have long speculated on its cause.
According to the Centers for Disease Control and Prevention, around 1 in every 68 children receives a diagnosis of ASD. The disorder is nearly five times more common in males than in females.
Brain development during pregnancy involves producing a cortex with six layers. The researchers found focal patches of disrupted development of these layers in a majority of the children who had autism. They were surprised at the similarity of the pathology, since patients with autism show a great diversity when it comes to symptoms and very complex genetics.
In subjects with autism, important genetic markers were missing in brain cells in multiple layers. According to the scientists, this indicates that the process of creating six separate layers of cortex with particular kinds of brain cells has been disrupted. Their analysis also showed that the defect did not occur uniformly throughout the cortex and most affected the frontal and the temporal cortex.
Scientists associate the temporal cortex with language. They link the frontal cortex to high functions like complex communication and understanding social cues.
The results suggest that the patchy nature of cortical defects instead of a uniform cortical involvement could at least partly explain why some autistic toddlers who get early and continued treatment show clinical signs of improvement. While the research leaves many questions yet to be answered about the occurrence of autism, its conclusions offer hope that additional knowledge of the defective patches could lead to a better understanding of how improvement occurs.
Vonda J. Sines has published thousands of print and online health and medical articles. She specializes in diseases and other conditions that affect the quality of life.