A technique that reads magnetic fields in the brain might provide a useful biomarker for diagnosing children with autism spectrum disorders.

As reported in the current issue of Autism Research, magnetoencephelography (MEG), a technology similar to electroencephalography (EEG) but which detects magnetic fields in the brain instead of electrical signals, can help identify children with ASD by picking up a lag in brain response to sounds.

When played a beep at 200, 300, 500 or even 1,000 Hz - all sounds that fall within the range of human speech - children with ASD show on average a 11 millisecond delay processing the sound.

The lag in the auditory response, occurring more than 100 msec after noise exposure, came from the right hemisphere of the superior temporal gyrus, a part of the brain involved in auditory processing.

The findings were robust, with the delay used in the study - with a cut-off at 116 msec - correctly identifying autistic disorder children in around 86 percent of all cases.

Although it's too early for the scientists to know conclusively what is happening, they think the delay, although tiny, could possibly partly account for difficulties autistic children have with speech.

"If while processing a multi-syllabic word you're delayed on a little component of it, it'll cascade all the way through," Dr. Timothy Roberts, a radiologist at the Children's Hospital of Philadelphia and lead author of the study, tells DOTmed News. "You'll still be processing the "l", while the other children have moved on. It can make the acquisition of language that much harder work."

HOW THE STUDY WAS DONE

To do the study, the researchers tested the children to make sure they had proper hearing, and excluded those who had mental disabilities, as previous studies have indicated these could affect the lag, or delay in the auditory response, detected by MEG.

The researchers also tested the children for their language skills to see if that had an impact on how fast their brains responded to the computerized beeps. Surprisingly, they found that good language skills, as measured by a test administered to the children before the MEG exam, weren't associated with a shorter sound latency.

More language-intensive, complicated audio tasks do generally show a correlation with language skills, Dr. Roberts says, so he thinks these results suggest that with such a simple stimulus (a beep) the study is picking up a response that is "purely sensory."

And IQ, also thought to affect the results -- children with high IQ might simply have speedier brains -- didn't show much effect, either.

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