Defective Genes May Explain Uncontrolled Brain Growth in Autism: Scientific American

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The Ballooning Brain: Defective Genes May Explain Uncontrolled

Brain Growth in Autism

Autistic children's brains may grow too big, too soon. A new

study links this unusual growth to abnormal gene activity that

fails to prune unnecessary neural connections

By Ferris Jabr

http://www.scientificamerican.com/article.cfm?id=courchesne-gene-expression

As a baby grows inside the womb, its brain does not simply expand like a

dehydrated sponge dropped in water. Early brain development is an

elaborate procession. Every minute some 250,000 neurons bloom, squirming

past one another like so many schoolchildren rushing to their seats at

the sound of the bell. Each neuron grows a long root at one end and a

crown of branches at the other, linking itself to fellow cells near and

far. By the end of the second trimester, neurons in the baby's brain

have formed trillions of connections, many of which will not survive

into adulthood---the least traveled paths will eventually wither.

Sometimes, the developing brain blunders, resulting in

" neuro-developmental disorders, " such as autism. But exactly why or how

early cellular mistakes cause autism has eluded medical science. Now,

Courchesne of the University of California, San Diego, thinks he

has linked atypical gene activity to excessive growth in the autistic

brain....