MRI Studies
The Center for Autism Research has a long history of conducting studies aimed at better understanding brain structure and development in individuals with autism. Our MRI studies were the first to show that the cerebellum is commonly observed to be abnormal in individuals with autism (Courchesne et al., 1988), and the first to identify brain growth abnormality in the first year of life in infants with autism. Currently, researchers at the Center for Autism Research are conducting prospective MRI studies with children between 12 and 36 months of age. These children are showing signs and symptoms of autism but have not yet been definitively diagnosed with the disorder. This procedure is the only method currently available for directly examining brain development in children with autism right at the time when behavioral signs are starting to emerge.
In the first study from our laboratory to utilize this method (Courchesne et al., 2001) we found that whole brain volume appears to be normal at birth in children later diagnosed with autism, but that by 2 to 4 years of age 90% of children were found to have a brain volume larger than the normal average. In addition, we found that the amount of white and gray matter in the cerebrum was significantly larger in children with autism compared to controls, whereas older children and adults with autism did not exhibit excessive volumes in these regions.
In the cerebellum, white matter volume was observed to be about 38% greater in children with autism versus controls, and while volumes increased dramatically with age in control children, little increase was observed in children with autism. Cerebellar gray matter volume in children with autism did not differ from controls, although increases with age were observed in controls, but not in children with autism.
Other recent studies from our laboratory have examined the cerebral lobes in early life in autism (Carper et al., 2000; 2002). We observed that the early cerebral volume enlargement noted in 2 to 4 year-olds with autism appears to be greatest in the frontal lobes and closer to the normal average in the occipital lobes. Furthermore, an inverse correlation has been observed between frontal lobe volume and size of the cerebellar vermis in children with autism between 3 to 9 years of age meaning that children with an abnormally large frontal lobe volume also exhibited an abnormally small cerebellar vermis. These findings suggest that abnormal neural growth patterns early in development lead to a number of consequences in brain structure and function in autism.