Outside looking in: researchers open new windows on Asperger syndrome and related disorders.
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.
In a second experiment, 16 adults with Asperger syndrome rated self- and experimenter-produced tickles on the left palm as much more ticklish and unpleasant than 16 healthy adults did. The researchers speculate that people with Asperger syndrome and autism have a hard time comprehending sensations that become meaningful only after complex neural operations.
Difficulties at integrating information also play into the poor planning and mental inflexibility observed in autism-spectrum disorders, say Rachael Mackinlay of University College London and her colleagues in the June Brain and Cognition. In that group's study, 14 boys, all around age 11, who had Asperger syndrome or high-functioning autism floundered on a game in which they had to follow a set of rules to complete three sorting-and-coloring tasks in 3 minutes.
Compared with 16 boys of the same age who had no developmental problem, those with Asperger syndrome planned sorting-and-coloring strategies less effectively, ignored the game's rules more often, and found it more difficult to switch from one task to another.
Such planning problems often ease during adolescence for kids with Asperger syndrome, according to a team led by Francesca Happe of King's College London. Her group studied 32 boys with Asperger syndrome or high-functioning autism, and 32 boys with no developmental or attention problems. All participants ranged in age from 8 to 16 years.
Boys with no disorders consistently showed the best planning and task-switching skills. However, among boys with the autism-spectrum disorders, teens did better on several of the tests than younger children did.
Still, many adults with Asperger syndrome and related disorders struggle with personal organization. Mackinlay's group cites a mother of one such boy: "I bet he'll become a rocket scientist, but I'll probably have to dress him and drive him to work."
STEREOTYPE SAVERS People with autism-spectrum disorders concentrate on details and parts of what they perceive, thus often missing the big picture, psychologist Uta Frith of University College London proposed more than a decade ago. This fragmented focus--dubbed the weak-central-coherence theory--undermines face recognition and other facets of visual perception and social life.
Yet individuals with Asperger syndrome can still look at a face and assess characteristics such as trustworthiness, Frith and her colleagues find. Social pigeonholing of this kind provides a framework for daily encounters, even if you can't tell your brother from a stranger on the street.
Frith's team devised a task to examine how well a person makes general inferences about others. In various trials, participants were told to assess the age, physical attractiveness, socioeconomic status, or trustworthiness of men in photographs. A group of 16 adults with Asperger syndrome responded much as 24 healthy adults did when judging these attributes.
But participants with Asperger syndrome scored poorly when asked to discern what people must be thinking in scenarios devised by the researchers. Many scientists refer to this social aptitude as "theory of mind" and estimate that it emerges by about age 3 in most children. Firth hypothesizes that people with Asperger syndrome lack theory of mind as a result of a disturbance of their brain networks.
Frith's finding resonates with the idea, developed by Lawrence Hirschfeld of the New School for Social Research in New York City, that judgments about social groups to which people belong operate independently of reasoning about what goes on in other individuals' minds.
Volunteers with Asperger syndrome did encounter one problem in discerning the social attributes of people in pictures. They differed from others in their judgments of sexual attractiveness in a person of their own sex. That process requires taking the perspective of someone of the opposite sex, Frith proposes.
Consistent with Frith's weak-central-coherence theory, visual perception also takes a hit in Asperger syndrome. Neuropsychologist Marlene Behrmann of Carnegie Mellon University in Pittsburgh reports that individuals with autism-spectrum disorders generally do poorly at looking at items and then grouping them into meaningful wholes. For instance, in an image of a large letter S formed by lots of copies of the small letter h, they often identify only the h.
Similarly, according to experiments reported by Behrmann and her colleagues in the June Trends in Cognitive Sciences, impaired face recognition in autism-spectrum disorders arises from a tendency to break visual information into parts rather than to see whole entities.
Although Asperger syndrome tends to run in families, no specific genes have been linked to the condition. In 2004, Finnish researchers associated Asperger syndrome with nine stretches of DNA on six different chromosomes.
Psychologist Simon Baron-Cohen of the University of Cambridge in England argues that the genes involved in autism-spectrum disorders foster a souped-up version of brain processes, typically observed in men, that result in perceptual and social impairments. He has detected such brain processes in people with autism-spectrum disorders.
Preliminary support for his view comes from a study, directed by Baron-Cohen, of brain activity in symptomfree parents of children with Asperger syndrome and in adults who had no family members with developmental disorders. Each group contained six men and sex women.
The researchers used functional magnetic resonance imaging to measure the rate of blood flow, a reflection of cell activity, in each volunteer's brain during two tests. The first test entailed finding a shape, such as a box, embedded in a larger geometric design. The second test required looking at pictures of a woman's eyes and determining which of two words, such as concerned or unconcerned, best described her thoughts or feelings.
Parents of kids with Asperger syndrome scored lower than the other group did, especially on the embedded-shapes test. Men and women in the control group showed sex-specific patterns of brain activity, but all the Asperger parents displayed intensified versions of the male sex-specific response.
THE GREAT MYSTERY Wendy Lawson, a British woman diagnosed with Asperger syndrome, has written of her daily social interactions as "a great mystery." She describes having carefully studied other people's vocal tones and body language to figure out what they were feeling. Still, Lawson had no idea how to forge friendships.
She wrote in her book Life Behind Glass: A Personal Account of Autism Spectrum Disorder (2001, Jessica Kingsley,) "I wanted things to go by the rules--and my rules at that! My clumsy efforts usually ended in trauma."
In 2004, psychologist Emma Williams of the University of Surrey in Guildford, England, analyzed Lawson's and nine others' accounts of living with Asperger syndrome or high-functioning autism. Williams concluded that rather than lacking a theory of mind, as proposed by Frith, people with these conditions theorize ponderously about what others think and feel.
Each writer in Williams' study describes explicit efforts to analyze social situations and generate rules or a library of visual images that can be consulted to understand and predict people's behavior in new encounters, Williams says.
Children don't typically develop a theory of mind as scientists might, she argues. Instead, social learning occurs "on the fly" during interactions with caregivers from infancy onward, she says. Children's emotional reactions serve as intuitive guides to others' intentions and feelings, and typical kids eventually become empathic experts who deal flexibly with people in all sorts of contexts and situations.
In contrast, children with autism-spectrum disorders lack the tools to become empathic experts, so they try to follow rigid rules of conduct. "When rules are the only thing we can go by, our activity becomes inflexible and distressingly prone to failure," Williams remarks.
Psychologist Ami Klin of Yale University School of Medicine agrees. He has found that people with autism disregard basic social cues, such as the movements of other people's eyes. The children end up theorizing awkwardly about what other people are up to, Klin hypothesizes.
However, these kids can solve problems that have specific solutions, so they often pass theory-of-mind tests, such as recognizing where a child will look for a hidden toy, Klin says.
In a new study, Klin and his Yale colleague Warren Jones found that 40 youngsters with various autism-spectrum disorders had great difficulty recognizing that an animated movie of moving geometric shapes represented various social encounters, such as one shape chasing another or starting a fight.
In contrast, the kids, all around age 13, easily recognized that another animated scene with geometric shapes portrayed the launching of a rocket into space and the rocket's orbit around a planet.
"Autism-spectrum disorders primarily involve a social deficit," Klin says. "It makes for a very difficult life."
LOTS OF PIECES Despite much new research on autism-spectrum disorders (SN: 8/5/06, p. 86), scientists know little about the neural roots of the problems, Belmonte says. As illustrated by Jason and Brian, the same genes can lead to brain connections shattered in different ways.
Weak-central-coherence theory and other theories of how people with the disorders think need to be unified with theories of how their brains develop, Belmonte holds.
"The irony is that we who study autism-spectrum conditions suffer from a sort of weak central coherence ourselves," he says. "This science is fractionated, and we often don't understand how the pieces fit together."
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|Date:||Aug 12, 2006|
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