New study highlights differences in autistic brains

The brains of people with autism respond erratically to sights, sounds and touch, unlike those of others, a new study shows. That difference might explain such autistic behaviors as repetitive motions and the urge to learn detailed information about narrow topics.

The study was published Thursday in the journal Neuron.

"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, speculated 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 to the sensory signals, but the people with autism were all over the lot, Behrmann said. Some of them 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, she and Heeger 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."

Higher-functioning children with autism may be "drawn to a learning style where they learn a lot of details that are very closely associated with each other and they end up knowing an enormous amount of detail about a very narrow topic, and that too could be a compensating strategy for controlling this unreliable brain response," he said.

Both Behrmann and Heeger stressed that they are speculating about the link between these behaviors and the brain imaging results they saw in the new study. They hope to design further experiments to test their hypothesis.

The study also involved researchers from the University of Pittsburgh and the Weizmann Institute of Science in Rehovot, Israel.