Children with autism spectrum disorders (ASD) often start their lives with delayed language development. However, some of them go on to acquire normal language and speaking skills by the time they are toddlers, while others continue to lag. Why does this difference exist? A new study now suggests that there is a link between language development in children with ASD and the activity of certain brain regions. A combination of brain scans and skills testing could help predict an autistic child’s language development, scientists say in the April 22nd issue of Neuron.

A team at the University of California, San Diego was led by Eric Courchesne, Ph.D., and included Lisa T. Eyler, Ph.D., a 2001 NARSAD Young Investigator grantee. The scientists monitored language skills development of 24 children who were developing typically and 79 children with early signs of ASD, 60 of whom were later definitively diagnosed with the disorder. The study began at the children’s one-year checkup and continued until age three or four. Soon after the start of the study, the scientists also conducted functional magnetic resonance imaging (fMRI) on the children to look at neural activity in brain regions usually associated with language development. The fMRI scans were performed while the children were asleep but their brains were still able to detect the sound of spoken words, as evidenced by brain activity seen in the scans.

Dr. Eyler and her colleagues report that brain activity in these language-sensitive regions is surprisingly similar between children without ASD and those who have ASD but go on to develop good language skills. Children with ASD and poor language skills show lower levels of early activity in these regions, particularly in a part of the brain called the left-hemisphere superior temporal cortex. The researchers also looked at how brain activity at the start of the study was related to differences among individuals within each of these subgroups in terms of their language ability early on and at later ages.  At the start of the study, among those children who developed typically, those who performed best on language tests had the highest levels of brain activation in areas of the brain related to language, memory, and emotion and the least amount of activity in parts of the brain related to motor skills. In children with ASD, the pattern was reversed: those with better early language skills had lower levels of language-related brain activity, and higher levels of motor-related activity. However, by age three or four, children with ASD who had developed good language skills had a relationship between early brain activity and language performance that was more like that of typically developing children. Children with ASD and poor language skills, on the other hand, maintained the “reverse” pattern of brain-behavior association throughout the study.

Dr. Eyler explains the complex experiment this way: "Not only did the group of children who went on to have poor language skills differ from typically developing children in the level of brain response early in life, the nature of the link between brain response and performance in this subgroup was opposite to that seen in the group of typically developing children. This was true when examining both early and later measures of language performance and how these related to the early measures of brain function."

The researchers hope their study will help doctors and scientists understand why language and other types of behavioral development can differ so much among children with ASD. Now that they have uncovered a biological basis for one of those differences, they want to use that information to better define different types of ASD and to look for targeted ways of treating the disorders in the future.

Read the abstract.