Approximately one in 68 children is identified with some form of autism, from extremely mild to severe, according to the U.S. Centers for Disease Control. On average, diagnosis does not occur until after age four, yet all evidence indicates that early intervention is the best way to maximize the treatment impact. Various tests that look for signs of autism in infants have not been conclusive but a new exercise could improve early diagnosis, and also help reduce worry among parents that they did not intervene as soon as possible.
The two most widely used tests to measure symptoms, the Autism Observation Scale for Infants (AOSI) and the Autism Diagnostic Observation Schedule (ADOS), cannot be used before the ages of 12 or 16 months respectively. The AOSI measures precursors to symptoms, such as a baby’s response to name, eye contact, social reciprocity, and imitation. The ADOS measures the characteristics and severity of autism symptoms such as social affectation and repetitive and restrictive behaviors.
Now a group of scientists at the Babylab at Birkbeck, University of London think they have identified a marker that can predict symptom development more accurately and at an earlier age: enhanced visual attention. Experts have long recognized that certain individuals with autism have superior visual skills, such as increased visual memory or artistic talent. Perhaps the most well known example is Temple Grandin, a high-functioning woman with autism who wrote, “I used to become very frustrated when a verbal thinker could not understand something I was trying to express because he or she couldn’t see the picture that was crystal clear to me.”
The Babylab researchers undertook a longitudinal study in which they tested both visual attention and autism symptoms in infants at nine months, 15 months, and two years. They followed a group of 82 high-risk and 27 low-risk infants. High-risk babies have an older sibling diagnosed with autism; those with low-risk have no mental or medical conditions and no first-degree relatives with an autism diagnosis. The researchers measured infant markers of autism symptoms using the AOSI at nine and 15 months, and measured symptoms and behavioral characteristics using the ADOS at two years.
At each session, the investigators showed the babies a short animation that focused the child’s gaze at the center of a screen. Then an image would appear containing a target that was the “odd-one-out.” For example, in a circle of seven “X”’s an “O” or plus sign might appear. The researchers tracked the infants’ gazes, measuring the time it took for them to look toward the odd target.
The scientists then compared the proportion of trials in which the infants looked toward the target with their scores on the symptom scales. The data showed that visual search performance at nine months had significant positive correlation with AOSI scores. In other words, the kids who at nine months quickly identified the odd visual element were more likely to show early symptoms of autism on the AOSI test at 15 and 24 months. The researchers found, however, that visual search performance did not directly correlate with ADOS scores at two years. In essence, although enhanced visual perception at nine months can predict the presence of autism symptoms later, it does not predict future symptom severity
This study, published in Current Biology on June 11, is part of the larger efforts of the British Autism Study of Infant Siblings (BASIS) program in the U.K., a consortium dedicated to tackling the challenge of identifying infant roots of autism to allow for earlier intervention. (In the U.S., a similar effort is being undertaken by the Autism Centers of Excellence (ACE) Program).
Yet there is still little understanding of how symptoms develop. Children diagnosed with autism, for example, may show enhanced performance in a visual task as early as 2.5 years. The new findings from Babylab corroborate evidence of unusual attention and perception and atypical function of brain regions that regulate these processes in infants, prior to being diagnosed with autism. Future research is necessary to establish whether superior attention and perception is a precursor to other autism symptoms or is simply another symptom itself.
The findings also support a shift in how the scientific community regards the development of autism symptoms. Most research has focused on the behavioral characteristics of autism measured by the AOSI and ADOS, such as language and social impairment. This limited focus supports the “social brain” theory of autism, which states that the social and cognitive deficits observed in people with autism result from impaired interactions with caregivers due to poor connectivity between specific brain regions collectively known as the “social brain” network.
The new results, however, suggest greater importance of brain regions involved in nonsocial processes. And they add to evidence for early signs of autism, “especially given that social and nonsocial developmental domains may not be as strongly differentiated in infants as they are in older children,” says Katarzyna Chawarska, a developmental neuroscientist at Yale University who was not involved in the study. The researchers who measured eye-tracking say that nonsocial markers may be useful additions to screening tests.
Furthermore, although current screening tests look for impaired brain function in infants, this study demonstrates a marker of enhanced function. Functional impairments can indicate other neurological disorders such as attention-deficit hyperactivity disorder or learning disabilities. Enhanced brain function, however, is “likely specific to autism and would provide a more specific screening target,” says Rachael Bedford, a developmental psychologist at King’s College London and a contributing author of the study.
But there are caveats. Studies of the developmental precursors of autism, including the Babylab study, have only measured individual markers and their connection to symptoms. Future research is needed to establish the accuracy of combinations of risk markers in predicting symptoms and symptom severity. Such research could allow doctors to anticipate a child’s future characteristics if, for example, “certain types of symptoms are more strongly predicted by specific markers,” says Elizabeth Milne, a psychologist at the University of Sheffield in England who was not part of Babylab.
A more comprehensive profile of precursors and symptoms could lead to more effective models of prediction and intervention — ones that would allow doctors to identify more accurately and at an earlier age which infants may go on to develop autism and what the characteristics and severity of their future symptoms might be. Ultimately, better tests will provide parents with the comfort that they intervened as soon as they could and that as a result, their children will get the treatment and care necessary to promote the highest quality of life possible.