November 14, 2011

Autism: ‘Prenatal Process Gone Awry’

(Ivanhoe Newswire) -- The exact causes of autism remain unknown, but failure of a vital prenatal process may be one of the culprits. A new study, published in the November 9 issue of the Journal of the American Medical Society (JAMA), confirms this relatively recent theory.

The study, by researchers at the University of California, San Diego Autism Center of Excellence, shows that brain overgrowth in boys with autism involves excess neurons in areas of the brain associated with social, communication and cognitive development.

"Brain imaging studies of young children with autism have shown overgrowth and dysfunction in the prefrontal cortex as well as other brain regions," lead researcher Eric Courchesne, PhD, professor of neurosciences at the UC San Diego School of Medicine and director of the Autism Center of Excellence, was quoted as saying.

"The underlying cause at the level of brain cells has remained a mystery," Courchesne continued.

The prefrontal cortex is the part of the brain involved in social, language, communication, affective and cognitive functions - functions mostly disrupted in autism.

Courchesne and colleagues compared postmortem tissue from the prefrontal cortex of seven boys with autism, ages 2 to 16 years, to that of six typically developing boys.

"An excess of brain cells was found in each child with autism that we studied," Courchesne was quoted as saying.

The scientists discovered a 67 percent excess of cortical cells - a type of brain cell only made before birth - in children with autism. The findings suggest that the disorder may arise from prenatal processes gone awry, according to Courchesne. The brains of the autistic children also weighed more.

"Because new cortical neurons are not generated after birth, the increase in neuron numbers in children with autism points to prenatal processes," Courchesne was quoted as saying.

An excess of these neurons is normal, and exponential between 10 and 20 weeks gestation. However, during the third trimester of pregnancy and early life of an infant, half of those neurons are normally removed in a process called apoptosis (cell death). Failure of that key early developmental process would create a large pathological excess of cortical neurons, Courchesne explained.

"While we think that ultimately not every child with an autism disorder will show this, our study does suggest that an abnormal excess of cells may be quite common among children with autism," Courchesne was quoted as saying.

"This is an exciting finding because, if future research can pinpoint why an excessive number of brain cells are there in the first place, it will have a large impact on understanding autism, and perhaps developing new treatments," he concluded.

SOURCE: JAMA, published online November 8, 2011