Some autistic children experience great difficulty with language, while others are able to acquire near-normal language skills. Scientists have never been able to explain the reason behind these differences. Now, UC San Diego School of Medicine researchers say they can predict an autistic child’s future language development abilities based on the results of a brain scan taken when they are toddlers.

Autism spectrum disorder affects about one in every 68 children in the United States, mostly boys. This neurodevelopment disorder ranges across all ethnic groups and socioeconomic levels. While some autistic kids show delays in language development, over time they acquire skills and begin to show substantial improvement as they grow older. Sadly, other kids display severe symptoms of the disorder; their acquisition of language progresses much too slowly and also may shrink over time. Throughout their lives, these more afflicted individuals become only minimally verbal.

Because no one fully understands the underlying reasons for the disorder, researchers find it difficult to arrive at an organic reason for these differences. At the same time, treatment quantity and quality do not explain the variations, either. Only one thing is clear: Early intervention would likely help those with the most severe symptoms.

This study, then, is an attempt to identify those autistic children who are most likely to lag behind when learning to speak and process language. To accomplish this, the researchers looked at brain scans of both autistic children and a group of typically developing children. Specifically, the researchers examined fMRI measurements taken in response to spoken language when the children were between the ages of 1 and 2 and compared these scans to assessments of each child’s language skills at ages 3 and 4.

Predictably, the brain scans of autistic toddlers who, at an older age, showed almost normal language skills were similar to the typically developing comparison group. Both showed robust responses to spoken language in a region of the brain responsible for processing sounds — the superior temporal cortices.

By contrast, the superior temporal cortices of autistic toddlers with poor language skills showed abnormal inactivity whenever they heard someone speak.

Balancing Act of Brain Networks

However, this was not the only difference between the brain scans of these toddlers. Interestingly, the brains of autistic toddlers with poor language development skills also showed strikingly different relationships between entire network systems.

In the typically developing children (and also the lightly afflicted autistic children), a trade-off occurred between two large-scale brain systems whenever they listened to (and processed) spoken language; their brains strongly engaged the brain system governing reward, emotion, and memory, while allowing the somatomotor areas and primary visual areas to fade, so to speak, into the background.

Unaccountably, the reverse was true in severely-afflicted autistic children. Processing language, their brains engaged the primary visual areas and motor areas, while their reward, emotion, and memory networks showed little activity.

Source: Lombardo MV, Pierce K, Eyler LT, et al. Different Functional Neural Substrates for Good and Poor Language Outcome in Autism. Neuron. 2015.