Narrowing Down The Cause: Excess Neurons Linked To Autism

Children with autism have larger brains and more neurons for their age than is normal, results of a small preliminary study indicate.

Neurons form pathways in the brain to process and transmit information by electrical and chemical signaling.

This study of brain cells in children with autism comes one step closer to answering a key question – whether the condition originates in utero or after birth in toddlerhood.

Autistic children were found to have about 67% more nerve cells in a part of the brain known as the prefrontal cortex than children without autism, in a study reported in the Journal of the American Medical Association (JAMA) by scientists at the University of California, San Diego.  The prefrontal cortex is responsible for communication, cognitive functions, decision making and moderating correct social behavior – areas which autistic children have difficulty with.

Lead researcher Eric Courchesne studied the brains of seven autistic boys between the ages of 2 and 16 post mortem and used analysis of the brains of six unaffected boys who died at similar ages to compare.

Although larger brain sizes in children with autism is not a new discovery, this is the first study that may have found which type of brain cells are responsible.

Neurons in all areas of the brain except those responsible for smell, memory and navigation are generated before birth.  “The present findings add significantly to mounting biological evidence that the developmental neuropathology of idiopathic autism begins before birth in some, possibly all cases,” Janet E. Lainhart, MD of the University of Utah in Salt Lake City, and Nicholas Lange, ScD, of the Harvard University Schools of Medicine and Public Health in Boston, wrote in an accompanying editorial.

“Knowing that we have a specific type of defect that occurs very early in development really helps us to focus and sharpen the next steps in research to determine what caused the excess,” says Courchesne. And hopefully find new treatments that can help children and their families cope better with the symptoms of autism.

According to Courchesne this finding that autism children have excess neurons is quite surprising.

“When we think of the inability to handle complicated information, we usually think of too little in the way of connections or brain cells,” he says. “But this is just the opposite.”

This surplus of neurons may have led to problems with their ability to connect and communication with each other. Courchesne suggests this may be causing a lack of proper nerve connections in autistic children, slowing down and stopping normal active interaction between different parts of the brain.

This study shows an exciting new avenue for further research.  The sample of autism cases in this study wasn’t big enough to determine links with behavior. Also a wider sample would need to be gathered of the non-autistic cases that were being used for comparison.  Further research will also need to be done to see if similar results are also found in girls with autism.

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