Unlike normally developing and mentally retarded children, autistic 3- and 4-year-olds do not react to a picture of their mother but do react when they see a picture of a familiar toy, a University of Washington psychologist has found.
Geraldine Dawson will report her result Thursday in Minneapolis at the annual meeting of the Society for Research in Child Development. Her finding suggests that an impairment in face recognition may turn out to be one of the earliest indicators of abnormal brain development in autism.
Dawson, who directs the UW Autism Center, said human brains seem to be wired to be interested in faces and there appears to be a specialized system for face recognition.
"We know that even newborn babies are drawn to face-like stimuli. This inborn interest in faces is the start of social development," she said. "This new study tells us something very fundamental about abnormalities in autism. It may be an important clue to actual brain circuits that are not functioning properly. Since all of the children in the study reacted similarly to toys and only the children with autism had problems with face recognition, it tell us autism is not a global problem. Rather, it indicates an abnormality in those brain circuits responsible for social function. It highlights that autism is a disorder of the social brain." Dawson said the idea that face recognition may be hard-wired, or something people are born with, is controversial.
"Just as with language, the brain comes with a readiness to recognize faces. But it also requires experience. With autism there may be some other reason why children don't pay attention to faces. They may not find it rewarding, and then that part of their brain does not develop further."
The region of the brain that appears to be specifically devoted to face recognition is the right fusiform gyrus, located in the temporal lobe, according to Dawson.
To learn how the brain operates, Dawson used a device called a geodesic net that looks like a hairnet and fits over the head. It records electrical brain impulses from 64 places on a child's scalp. Similar devices for adults record data from 128 locations. Dawson's study involved 34 children with autism, 21 normally developing children and 17 with mental retardation but no autism. Some autistic children also are mentally retarded.
Each of the children was shown two sets of images - faces and objects - about 50 times. First they were shown digitized photos of their mother or a stranger. Then they were shown digitized photos of a favorite or an unfamiliar toy. The net measured brain activity half a second after each image was shown and picked up the specific brain signal to that stimulus.
Earlier research has shown that normally developing children as young as 6 months old show different brain activity when they see their mother and when they see a stranger. Dawson's research revealed a similar pattern among normal and mentally retarded 3- and 4-year-old children, but the autistic children failed to recognize their mother. However, all three groups exhibited similar reactions when they saw images of a favorite toy versus an unfamiliar one. She believes the ability to recognize faces may turn out to be a key tool in identifying children with autism. Previous research by Dawson has shown that a child's failure to look at faces at age 1 is the best predictor of autism.
"Today we can reliably identify autism in children at age 2, but it is difficult to identify babies with autism," she said. "What usually catches parents' attention around 12 months is that their child is not picking up language. Parents are also especially sensitive to picking up autism symptoms in a younger sibling. Siblings of children with autism have 1-in-20 odds of having autism."
Dawson, whose research was funded by the National Institute of Child Health and Human Development, next plans to replicate the mother-stranger picture study with 18-month-old autistic toddlers to see if this identification process operates at an earlier age. Also being reported at the Minneapolis meeting is related research by Dawson and UW doctoral student James McPartland that shows adults and adolescents with autism have abnormal reactions to faces. The Autism Center is part of the UW's Center on Human Development and Disability. Dawson and an interdisciplinary team are attempting to find the neurobiological and genetic causes of autism and design interventions to help autistic children.
Autism and related disorders are among the most common developmental disabilities, occurring in one in 500 people. Autism is characterized by an impaired ability to communicate or relate socially with others. People with the disorder typically have a limited range of activities and interests.
Materials provided by University Of Washington. Note: Content may be edited for style and length.
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