Brain Imaging Reveals New Clues To Autism
Imagine living in a country where you don't know the language—trying to fit in when you don't understand the customs, the gestures, or the common context of a society everyone else shares.
That feeling would probably be familiar to someone living with an austism spectrum disorder (ASD).
Until recently, very little has been known about what autism is and how it works. Its causes are poorly understood, and even its prevalence seems to have been significantly underestimated.
Now fMRI and diffusor tensor (DTT) imaging are providing a clearer picture of what is happening in autism in the brain at work. These insights could provide important clues to the causes of autism and new research targets for treatment.
"With the fMRI, we can see differences in blood flow in the brain as people with ASD's perform tasks," said Rajeskh Kana, PhD, director of UAB's Autism Brain Imaging Research Laboratory. "There's less connectivity in white matter. People with ASDs don't seem to be retrieving as much information from multiple areas of the brain. When we look at water diffusion along the axons, we see the same thing. Regions of the brain aren't connecting as well as they should."
Reduced connectivity between Broca's and Wernicke's areas was evident in reactions to humor based on word plays that require access to multiple meanings in different contexts.
"When control subjects hear 'He said he lost his job at the orange juice factory because he couldn't concentrate,' they laughed. Subjects with high functioning ASDs didn't understand the joke, and didn't show the same levels of activity in multiple areas of the brain, " said Kana.
Differences were also apparent in the processing of information from the physical world and social situations.
"When we showed people with high functioning ASD's a cartoon vignette of a glass falling, they were able to choose a picture of a broken glass as the next frame. But when we showed them a woman watching a street musician and opening her purse, they couldn't predict whether the next frame should be her giving the coin to the musician or putting it in a parking meter," Kana said.
People with autism seem to have difficulty reading facial expressions, body language and simulating other people's feelings to understand their intentions. They can see details, but have difficulty putting them together to see the big picture.
"Babies are born with more white matter than they need, but at around the age of two, the body begins pruning white matter connections that aren't used. That's another reason early diagnosis is so important," Kana said. "If we can intervene early enough, we might be able to teach them to strengthen those connections to gather better information. Something as simple as learning to use direct eye contact could make a difference."
Early diagnosis can be difficult, particularly in families with economic disadvantages. Even getting an accurate estimate of the prevalence of autism can be a challenge.
"In 1990 autism was thought to affect one person in 2,000. The 2006 CDC data shows one in 110 eight-year-olds have an ASD. In the most recent data that will soon be released, we expect the prevalence to be even greater," said UAB professor Beverly Mulvihill, PhD, who gathers data in Alabama.
" Some of the increase is from increased awareness in the community, and from expanding the definition to include Asperger's Syndrome and other disorders. We haven't been able to determine whether the actual risk is increasing. However, we found that boys are 4.5 times more likely than girls to have an ASD. There seems to be a genetic link that could be triggered by other factors," Mulvihill said.
Healthcare providers, families and educators often find themselves at odds over differences in the medical definitions of ASDs and how it is defined in education. Parents of children with Asperger's Syndrome sometimes become upset and recruit their doctor's help in communicating the diagnosis to teachers when school records indicate that their child has autism.
"There isn't a separate category for Asperger's in programs funding special education services. It's all listed under the heading of autism," said Mulvihill. "When the next Diagnostic and Statistical Manual (DSM5) is published, it's likely that it will all fall under Autism Spectrum Disorder, since it's difficult to say where autism ends and Asperger's Syndrome begins. What's important is that the diagnosis comes early so intervention can begin."
To assist in early recognition and referral, Sarah O'Kelly of UAB is working under a grant from the CDC to adapt their "Learn the Signs. Act Early." campaign to include Alabama-specific resources. When complete, the materials will be available to people who interact with children to help those with autism receive early referral and intervention to give them the best opportunity to build a stronger foundation and live a fuller life.