New research reported in the Journal of the American Medical Association (JAMA) suggests that autism may originate in utero, not toddlerhood, as many have long believed. Scientists at the University of California, San Diego, found that autistic children have about 67 percent more nerve cells than do other kids in the prefrontal cortex, a part of the brain that is involved in processing language, social behavior, and decision-making, reports TIME.com.
In this small, preliminary study, researchers looked at postmortem brain tissue from seven boys with autism and six without it, ranging in age from 2 to 16 when they died (from drowning or other accidents; determining how many neurons are in the brain can only be done after death). Researchers were surprised by their findings of an excess of neurons, given that deficits in social skills, like those typically exhibited by children affected by autism, are generally linked to less nerve tissue.
“When we think of the inability to handle complicated information, we usually think of too little in the way of connections or brain cells,” said lead researcher Eric Courchesne, PhD, a professor of neurosciences at the UC-San Diego School of Medicine and director of the Autism Center of Excellence. “But this is just the opposite.”
Dr. Courchesne explained that autistic children may have insufficient nerve connections because the excess of neurons may have created difficulty in their ability to connect and communicate with each other.
These findings are important because neurons or nerve cells start developing in the prefrontal cortex at the end of the first trimester of pregnancy—but do not continue after birth, meaning that events after birth couldn’t have created such an oversupply of neurons. (Neurons are generated after birth in just two parts of the brain: in the hippocampus and in the olfactory bulb.)
Although this was a small study, “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,” said Dr. Courchesne.