Outside looking in: researchers open new windows on Asperger syndrome and related disorders

Science News,  August 12, 2006  by Bruce Bower

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In 2003, neuroscientist Matthew K. Belmonte documented the daily lives of a pair of 13-year-old identical twins with an unusual bond. Both twins have Asperger syndrome, a disorder related to autism and characterized by social cluelessness, repetitive behavior, and unusually narrow interests. Intriguingly, one of these intelligent, genetically alike boys displays a much more severe version of Asperger syndrome than the other does.

The twin with the lesser difficulties--call him Brian--can play with other kids but feels anxious and shy with people he doesn't know. When Brian joins in conversations, he sometimes asks inappropriate questions or suddenly stops talking. He likes to spend time alone at the end of each school day. Brian focuses well on daily tasks, although sequences of instructions can confuse him.

His brother--call him Jason--is even less successful socially. When he tries to play with other kids, he fails miserably. Even with people he knows, he usually feels anxious, rarely smiles, and avoids looking them in the eyes. Like his brother, Jason finds social games confusing and prefers to spend time alone. His stilted conversations typically include inappropriate questions and comments.

Jason, but not Brian, laughs inappropriately. Although he recognizes that problem, he can't change his behavior. During the day, Jason gets confused more often than Brian does.

Both of the boys often trip over their own feet and lack hand-eye coordination.

Birth complications may explain the differences between the brothers, Belmonte says. Brian had no problems at birth, but Jason didn't breathe until physicians administered oxygen.

That brief loss of oxygen altered Jason's brain development in ways that worsened Asperger syndrome, Belmonte proposes. Brain scanning he conducted with Ruth A. Carper of the University of California, San Diego shows that compared with Brian, Jason has a smaller brain overall, a smaller right cerebellum, and a disproportionately large left frontal brain. During a mentally challenging task, Brian's pattern of brain activity is intermediate between that of normal kids and that previously observed in children with autism. Jason's brain activity is so disorganized that it doesn't resemble either pattern.

Belmonte's investigation of Jason and Brian belongs to a new wave of research on Asperger syndrome and related disorders. Autism, the most prominent condition in this category, impairs the ability both to communicate and to interact with others, whereas in Asperger syndrome, the problems are primarily social. Autism may include a low IQ or, in high-functioning people with the disorder, an average IQ.

An estimated 1 in 166 children now receives a diagnosis of autism or a variant of it. Those with Asperger syndrome are in the minority, but their prevalence hasn't been accurately measured. The incidence of disorders in the autism spectrum has increased in the past decade. Explanations of that increase remain controversial.

Asperger syndrome is beginning to receive nearly as much scientific attention as autism does. Published in the June Brain and Cognition, Belmonte's observations and other new investigations are beginning to document the unusual sensory world of people with Asperger syndrome and the ways in which this condition undermines a person's ability to plan, carry out daily tasks, recognize faces and the emotions behind them, and interact with others. Brain-scan data suggest that kids with Asperger syndrome inherit a genetic propensity to develop this condition from their symptom free parents.

Other evidence suggests that people with Asperger syndrome focus on details and miss the larger picture, especially in social situations.

These findings shed some light on the complex worlds of Asperger syndrome and autism, says Belmonte, who's now at Cornell University. He notes that there aren't clear boundaries between the various sets of symptoms. "It sometimes seems that there as many kinds of autism-spectrum conditions as there are people diagnosed with them," he remarks.

TOO MUCH TOUCH People with autism-spectrum disorders often can't tolerate cold, heat, pain, tickling, itching, certain textures on clothing, and even the touch of other people. As Gunilla Gerland wrote in a 1997 memoir of living with Asperger syndrome, "To be just lightly touched appeared to make my nervous system whimper, as if the nerve ends were curling up."

Sensitivity to touch and difficulties in planning and social interactions reflect underlying problems in dealing with rapidly changing circumstances, researchers now propose. The touch responses reflect a heightened sensitivity to high-frequency vibration of the skin, suggest Sarah-Jayne Blakemore of University College London and her coworkers.

Blakemore's group used a vibrating device to stimulate the tip of the left index finger on 10 adults with Asperger syndrome and 9 adults who had no developmental disorder. Individuals with Asperger syndrome showed much more sensitivity and discomfort to high-frequency vibrations--but there was no difference between the groups when low-frequency vibrations were applied.