Whether autism begins while a child is still developing in a mother’s womb, or whether something happens after a child is born that causes the neurodevelopment disorder, has been the subject of much debate. A recently published article in the Journal of the American Medical Association (JAMA) lends further weight to autism starting before a child is born.
Researchers under neuroscientist Eric Courchesne examined the postmortem brain tissue of 13 boys, aged 7 – 16 years old, seven of whom were autistic and six who were not. The autistic children had an average of 67 percent more neurons, a type of brain cell, and in a certain region of the brain, the prefrontal cortex, which processes complex behaviors including language, decision-making and social behaviors. Specifically, the autistic children had 1.94 billion neurons in their prefrontal cortex, versus 1.16 billion in a child who is not autistic. The brains of the autistic boys had 79 percent more neurons in the dorsolateral prefrontal cortex, which is linked with executive functioning, such as planning and reasoning. They also had 29 percent more neurons in the mesial prefrontal cortex, which is associated with emotions and social behaviors.
In other words, the parts of the brain in which the autistic children had a noticeably high number of neurons are associated with areas, such as language and social behaviors, that autistic individuals are challenged in, sometimes severely. As Dr. Max Wiznitzer, a neurologist and autism expert at the Rainbow Babies and Children’s Hospital in Cleveland, Ohio, comments,
“This is a good example where you have too much of a good thing, it can be bad for you.”
Dr. Wiznitzer provided this metaphor to explain:
He likens the brain to an assembly line with too many workers (brain cells) sitting around. And when you have too many workers on the line, they can interfere with one another rather than contribute to the factory’s (or brain’s) productivity. Wiznitzer agrees that even though this is a small study, it’s consistent with previous research.
Neurons, says Courchesne, are only generated during fetal development, and specifically between 10 and 20 weeks. The number of neurons a person has remains the same, but the neurons grow in size and form connections. After the second trimester, neurons are “pruned,” which is to say, they undergo “planned cell death.” As Lizabeth Romanski, an associate professor of neurobiology and anatomy at the University of Rochester Medical Center who did not participate in the study says, what needs to be found out now is “whether autistic brains generate more neurons, or if they have a malfunctioning ‘pruning’ process.”
Research offering proof that autism beginning before birth would help lay to rest heated debates about autism’s causes, such as that a vaccine or other external agent “makes” a typically developing child “become” autistic.
Courchesne is a professor at the University of California San Diego School of Medicine and director of the Autism Center of Excellence. He says that the study provides some “really solid” evidence that autism has a prenatal origin.
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