The brains of people with autism respond erratically to sights, sounds and touch, unlike those of others, said a study published Thursday in the journal Neuron. That difference might explain such autistic behaviors as repetitive motions and the urge to learn detailed information about narrow topics.
"Imagine you have the experience that your world is completely unreliable," said New York University psychologist David Heeger, one of the study’s authors. "Every time you look at something it looks slightly different, or every time you hear something you hear it slightly differently."
That might make the world a scary place for those on the autism spectrum, said Heeger and Marlene Behrmann, a co-author and an autism expert at Pittsburgh’s Carnegie Mellon University.
In the study, 14 high-functioning adults with autism and 14 people without the disorder did a task while lying in a magnetic resonance imaging machine. As they stared at a computer screen, they saw patterns of dots, heard a series of beeps and felt puffs of air on their hands. Scientists watched how their brains responded to the simple stimuli.
The typical people had fairly predictable brain responses, but the people with autism were all over the lot, Behrmann said. Some reacted strongly to the sounds but weakly to the dots, while others had erratic reactions to the same stimulus from one trial to another.
Variations in the brains of autistic people may help explain why some with the disorder are hypersensitive to noises or touch, or have trouble with balance and gait, Behrmann said. It also may be one reason why people with autism are more likely to have epilepsy.More broadly, it could be what underlies the repetitive motions that some children with autism make, or the fixation some of them have on developing expertise on such narrow topics as types of trains or baseball statistics, they said.
If an autistic child’s environment seems unpredictable, Heeger said, "one way to deal with that is you might repeat an activity that you can do over and over, and that might be comforting."
But they stressed that they are speculating about the link between these behaviors and the brain imaging results. They hope to design further experiments to test their hypothesis.