A new study provides evidence that autism is a complex brain disorder affecting virtually the entire brain. The finding replaces prior opinion that only brain areas that specifically dealt with social interactions, communication behaviors, and reasoning abilities were affected in autism.
Scientists in a research network supported by the National Institutes of Health (NIH), found autism to affects a broad array of skills and abilities, including those involved with sensory perception, movement, and memory.
The findings, appearing in the August Child Neuropsychology, strongly suggest that autism is a disorder in which the various parts of the brain have difficulty working together to accomplish complex tasks.
The study was conducted by researchers in the Collaborative Program of Excellence in Autism (CPEA), a research network funded by two components of the NIH, the National Institute of Child Health and Human Development and the National Institute on Deafness and Other Communication Disorders.
“These findings suggest that further understanding of autism will likely come not from the study of factors affecting one brain area or system, but from studying factors affecting many systems,” said the director of NICHD, Duane Alexander, M.D.
People with autism tend to display 3 characteristic behaviors, which are the basis of the diagnosis of autism, explained the study’s senior author, Nancy Minshew, M.D., Professor of Psychiatry and Neurology at the University of Pittsburgh School of Medicine. These behaviors involve difficulty interacting socially, problems with verbal and non-verbal communications, and repetitive behaviors or narrow, obsessive interests. Traditionally, Dr. Minshew said, researchers studying autism have concentrated on these behavioral areas.
Within the last 20 years, however, researchers began studying other aspects of thinking and brain functioning in autism, discovering that people with autism have difficulty in many other areas, including balance, movement, memory, and visual perception skills.
In the current study, Dr. Minshew and her colleagues administered a comprehensive array of neuropsychological tests to a group of children with autism. The researchers tested 56 autistic children, and compared their responses to those of 56 children who did not have autism. The children with autism were classified as having higher functioning autism–an I.Q. of 80 or above, and the ability to speak, read, and write. All of the children in the study ranged in age from 8 to 15 years. The purpose of the test array, Dr. Minshew said, was to determine whether there were any patterns in mental functioning unique to autism.
“We set out to find commonalities across a broad range of measures, so that we could make inferences about what’s going on in the brain,” Dr. Minshew said.
The researchers found that, across the entire series of tests, the children with autism performed as well as–and in some instances even better than–the other children on measures of basic functioning. Uniformly, however, they had trouble with complex tasks.
For example, regarding visual and spatial skills, the children with autism were very good at finding small objects in a cluttered visual field, on tasks like finding Waldo in the “Where’s Waldo” picture books series. However, when asked to perform a complex task, like telling the difference between the faces of similar looking people, they had great difficulty.
Although their memory for the detail in a story was phenomenal, the children with autism had great difficulty comprehending the story. Many were highly proficient at spelling and had a good command of grammar, but had difficulty understanding complex figures of speech, like idioms and metaphors.
“We see this with our patients,” Dr. Minshew said. “If you use an expression like ‘hop to it,’ a child with autism may literally hop.”
Other complex tasks were also difficult for them. The children with autism either had poor handwriting, or wrote very slowly. Many had difficulty tying their shoes and with using scissors.
“These findings show that you can’t compartmentalize autism under three basic areas,” Dr. Minshew said. “It’s much more complex than that.”
Dr. Minshew explained that the major implication of the finding is that when seeking to understand autism, researchers need to look for a cause or causes that affect multiple brain areas, rather than limiting their search to brain areas dealing with the three characteristic behaviors involving social interactions, communication, and repetitive behaviors or obsessive interests.
“Our paper strongly suggests that autism is not primarily a disorder of social interaction, but a global disorder affecting how the brain processes the information it receives–especially when the information becomes complicated.”
In previous research with an imaging technology known as functional magnetic resonance imaging, or fMRI, Dr. Minshew and her coworkers determined that adults with autism have abnormalities in the neurological wiring through which brain areas communicate. In those studies, the researchers found that people with autism had difficulty performing certain complex tasks that involved brain areas working together.
Dr. Minshew said that such abnormalities in brain circuitry provide the most likely explanation for why the children with autism in the current study have difficulty with complex tasks that require coordination among brain regions but do well on tasks that require only one region of the brain at a time.
The researchers undertook the current study as a follow up to an earlier study they did of adults with autism. The researchers studied children to determine if the features of autism were consistent throughout life, or changed as people with autism grow older. For the most part, the current study revealed that both adults and children with autism experience the same kinds of difficulties with complex tasks.
One difference is that adults with autism appear to score higher on tests involving sensory interpretation than do children with autism. Such tests would involve identifying a number traced on a finger tip, or identifying an object placed in one’s hand without looking at it. Dr. Minshew said that as people with autism grow older, they may have less sensory difficulty than they did as children.
Still, adults with autism fare much worse on tests of complex language and reasoning than do other adults. This gap in complex language and reasoning ability between the two groups is not as pronounced when children with autism are compared to other children. This is because children’s brains have not yet developed these skills, Dr. Minshew said. However, the gap widens with time. As typical children get older, they develop these higher order language and reasoning skills while adolescents and adults with autism do not.