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Newswise – Some of the hallmark characteristics of autism are the tendencies to avoid looking at other’s faces and making less eye contact. Many autistic individuals have a harder time remembering faces and recognizing facial emotions than their neurotypical counterparts. Researchers have been studying face processing in the brains of autistic people for decades. In the early 2000s, for instance, Yale-led research found that the brain regions involved in face processing were less active in autistic people than neurotypical people.
James McPartland, PhD, Harris Professor in the Child Study Center and director of the Center for Brain and Mind Health, uses electroencephalography (EEG)—which measures the electrical activity in the brain—to study face processing in autistic people. However, most EEG studies to date are confined to only specific areas of the brain.
Now, a new study including approximately 400 autistic children measured electrical activity across the entire scalp to more fully understand differences in face processing. The researchers, led by McPartland, found that signals associated with face processing were less distinct in autistic participants. Furthermore, in neurotypical children, signals associated with face processing become more refined with age—a trend they did not observe in autistic children.
“This is the first time we’ve leveraged the full volume of very rich information provided by an EEG recording to understand face perception and autism,” McPartland says.
Face processing is less distinct in autistic brains
Imagine trying to measure the amount of traffic in your city by setting up a camera at a single road downtown. “That’s the way most research on face processing so far has worked,” McPartland says.
The new study, he explains, is akin to using satellite imaging to track all of the cars in every part of the city. The researchers used participant data from the Autism Biomarkers Consortium for Clinical Trials (ABC-CT). In total, they studied autistic and neurotypical children of a range of ages. They used EEG to measure the brain activity of the participants in response to seeing images of faces and objects.
Importantly, they measured electrical signals across all 128 electrodes around the scalp. Then, the researchers used machine learning to try to predict what a participant was looking at based on the brain’s electrical activity.
The researchers found that it was easier to determine whether a neurotypical child was looking at a face than an autistic child. “The neural activity that we measure at the scalp is just not as distinct in autistic children,” says first author Jason Griffin, PhD, assistant professor of psychology at University of Houston. Griffin was formerly a postdoctoral researcher in McPartland’s lab.
Furthermore, in neurotypical children, the ability to predict what the participants were looking at increased with age. In autistic children, on the other hand, the researchers did not see any differences in brain activity with age. “Their face-specific processing is not following the same trajectory,” Griffin says.
The findings also broaden scientists’ understanding of when differences in face processing arise in autistic individuals. Face processing is a complex process that starts from the moment our eyes receive visual information and ends when we perceive whose face we’re looking at. Most research on face processing in autism focuses on a biomarker known as the N170, which refers to a shift in brain activity that occurs 170 milliseconds after seeing a face. This signature index of face perception is delayed in autistic individuals.
“But when you look at face processing through an approach that’s more inclusive of the full temporal range of information, we’re seeing that differences in autism occur even earlier,” McPartland says.
Improving diagnostics and supportive measures for autism
For many years, clinicians have tried to treat differences in face processing by insisting autistic patients make eye contact—which researchers now know doesn’t work. Understanding underlying developmental differences in the brain could give scientists better clues on how to support autistic people.
But one of the challenges of studying the biology of autism, the scientists say, is understanding which factors are caused by the condition itself, and which are caused by the experience of living with autism. The findings suggest that differences in face processing are due to the former.
“When we’re seeing this expected refinement and specialization in non-autistic people, we’re seeing a reduced developmental change in autistic people,” McPartland explains.
This suggests that interventions for helping autistic people better understand facial emotions, for example, might be the most effective in earlier childhood when these differences in development first arise.
Many neurodivergent people aren’t hindered by their autism and may not need or want intervention. But for others, difficulties in perceiving faces can impact their quality of life.
“Imagine navigating life when it’s hard for you to perceive the information in another person’s face, from navigating a playground to navigating a job interview,” McPartland says. “This is one of the critical areas that causes difficulty for many autistic people.”
Furthermore, there is a lack of biologically-based tools to evaluate patients for autism—clinicians diagnose the condition based on behavior. Researchers are now evaluating various biomarkers as candidates for the development of better diagnostic methods or to define subgroups. Understanding differences in face processing could help point to new diagnostics and help scientists predict who might be better candidates for interventions such as social skills therapy.
“This is a first step in introducing a new biomarker,” McPartland says.
Original release: https://medicine.yale.edu/news-article/how-autistic-brains-process-faces-differently/
