A research review published in the journal Neuron suggests that autism may begin with pre-natal brain injury to the cerebellum. Dr. Samuel Wang, associate professor of molecular biology at Princeton University, and his co-authors did a thorough review of existing research, and concluded that the cerebellum plays a larger role in early development than scientists previously believed.
The cerebellum is the part of the brain that connects the two hemispheres. It accounts for only 10 percent of the brain, but contains 50% of the brain’s neurons. It plays a strong role in coordinating the physical movements of the body, but Dr. Wang believes it also plays a role in processing the complex sensory information necessary to form normal social relationships and other cognitive functions.
Modern mapping techniques have allowed scientists to gain a better understanding of the connections between the cerebellum and the other parts of the brain. The cerebellum is known to help the brain send messages regarding physical coordination, but it is also likely that information regarding cognitive functions passes through it as well. If the information is unable to travel through the cerebellum to reach other parts of the brain, further development will be compromised. Dr. Wang found that children born with damage to the cerebellum had an increased risk of developing autism, similar to that of a smoker developing lung cancer.
One example of the derailment of social development is an infant’s response to a parent’s smile. There is no inherent reward in a parent or caregiver’s smile, but typically developing infants soon learn to associate it with a reward, such as food, a clean diaper, or cuddling. If the brain is unable to match the smile to the later reward, the child will not make the connection, and further social development will be compromised.
The authors of the study also found that there are important “sensitive” periods when these connections are most vulnerable, and that it is most likely that the damage occurs before birth. Another study published in the New England Journal of Medicine also reported changes in the cerebral cortex of children with autism that were believed to have occurred before birth. Dr. Wang says,
“Because the risk factor from cerebellar injury is bigger than any other known environmental risk, we think this provides deep insight into the basic biology of how ASD brains go off track. Problems in cerebellar function (whether caused by injury or genetic mechanisms) aren’t the cause of autism, but they are potentially a significant cause of autism.”
A greater understanding of the brain’s role in developmental disorders like autism may help researchers develop effective therapies for autism. Dr. Wang says,
“In the case of autism, the early-life cerebellum might be a target for future intervention. Autism researchers have been hacking away at the genetics for years, but genes are a far cry from brain circuits. There’s such a gap between genes and child development. I hope our article can help bridge that gap. “