Without a way to forecast whether the early warning signs of autism will develop into severe impairment, parents of children with the disorder are left with one harrowing option: Wait and see. Now, a new study suggests that a distinct ripple of brain waves measured while toddlers listen to words can reliably predict how they will fare in a range of cognitive areas up to age 6—the longest-term forecast yet achieved. In addition to pointing toward more effective treatments, the discovery could help reveal how early social abilities facilitate the development of language.
Many children with autism spectrum disorder (ASD) have begun to display telltale social and language deficits by the time they're toddlers; they fail to play or make eye contact with others, for example, or to say short sentences such as "drink milk." Although scientists have long considered the brain systems that govern these two types of deficits as separate, a growing body of evidence suggests that they are actually deeply intertwined, says Patricia Kuhl, a cognitive neuroscientist at the University of Washington, Seattle, and lead author of the new study.
One of Kuhl's first important clues that social deficits might hinder language acquisition in autism came from her 2005 study of "Motherese"—the exaggerated, sing-song baby talk that parents instinctively shower on their children. When given the choice between listening to samples of Motherese or computer-generated tones, Kuhl found that preschoolers with autism "actually preferred the Robovoice," she says. This lack of interest in human speech not only correlated with the severity of a child's autistic symptoms, Kuhl notes, but with a lack of typical brain response to subtle changes in syllables, such as the switch from "ba" to "da." That's bad news, she says, because "picking up these tiny changes means the difference between learning language or not."
Previous studies have shown that when a typically developing 20-month-old child hears a word that she doesn't know, a characteristic uptick in brain waves in the left hemisphere of the brain can be detected through electroencephalography (EEG), a noninvasive method of measuring the brain's electrical activity. To see if EEG responses to this language task would also track with social ability in children with autism, Kuhl brought 2 dozen 2-year-olds with ASD into her lab. While monitoring each child's brain activity through sensors attached to nylon caps, she and her team asked each child's parents which words he or she was familiar with, such as "car," "book," or "shoe," and listed those words along with unfamiliar ones such as "pint," or "guide."
On average, the children did not show the signature uptick in brain activity in response to unknown words, Kuhl says. When she divided them into two subgroups based on their scores on a standard test of social cognition, however, she saw a striking pattern. Children with the lowest scores on the social cognition tests showed atypical responses to the unknown words—no response at all, for example, or activity in a different part of the brain, while those with the higher scores showed a more typical pattern of brain activation in the left hemisphere, the authors report online today in PLOS ONE. What's more, a follow-up study found that more typical brain responses correlated "with near perfect accuracy" with higher scores on a range of cognitive tests at age 4, and even higher scores at age 6, Kuhl says.
The fact that Kuhl's team has discovered a brain measure that increasingly correlates with outcomes over time is "really exciting," says neuroscientist Kristen Gillespie-Lynch of the College of Staten Island in New York. "It shows that there could be brain signatures that predict who's going to do well." Ideally, "this information could be used to tailor treatment interventions from earlier ages than currently possible with behavior alone," adds neuroscientist Elizabeth Redcay of the University of Maryland, College Park.
The results fit well with other studies of how sociality can influence language skills, says Debbie Mills, a cognitive neuroscientist at Bangor University in the United Kingdom. In people with Williams syndrome, which is characterized by a strong drive for social interaction, she says, one sees an opposite electrical brain response to similar linguistic tests than that seen in people with autism.
In the past, researchers didn't take the influence of social interaction on other aspects of cognition very seriously, Kuhl says. "It was considered soft, or just voodoo." Now, she says, scientists are recognizing that just being near a fellow human can profoundly influence how we act, perceive, and learn. "The whole world changes when you're in the presence of someone else."