CHICAGO The brains of autistic children react to sounds a fraction of a second slower than those of normal children, which may help explain the communication problems associated with autism, researchers said on Monday.
"What this does is it provides strong supporting evidence for the emerging theory that autism is a problem of connectivity in the brain," said Timothy Roberts, vice chairman of research in the Department of Radiology at Children's Hospital of Philadelphia.
Roberts and his colleagues had 30 autistic children age 6 to 15 listen to a battery of sounds and syllables while monitoring the tiny magnetic fields produced by the brain's electrical impulses.
The test employed a technique, called magnetoencephalography (MEG), in which a helmet-like device is used to detect and locate brain activity. Only around one hundred devices exist that can monitor the tiny magnetic fields, Roberts said in a telephone interview.
In comparison to the tenth of a second response time in the brains of normal children in the study, the autistic children's brains were anywhere from 20 percent to 50 percent slower to react.
Since a single syllable in a multisyllable word might take less than one-quarter of a second to say, Roberts said 1/20th of a second extra delay in the response time of the brains of autistic children may hamper their ability to comprehend.
"There could be abnormal routing or a lack of connectivity in the brain," he said in a telephone interview. "It may be like a highway with traffic making it hard to get through."
"We think this (delay) is a signature or a biomarker that could be used to stratify autism patients," since autism is a spectrum of disorders that afflicts people to vastly different degrees, he said.
Microscopic examination of the brain tissue of people with autism has shown there may be fewer connections between their brain cells, said Roberts, who presented his findings at a meeting of the Radiological Society of North America.
Brain scans performed by the more frequently used magnetic resonance imaging or computed tomography are not detailed enough to detect such microscopic differences in brain cell connections. Such scans have not found structural or size differences between autistic and normal brains.
Autism, which is characterized by difficulty interacting with others and sometimes repetitive behaviors, occurs in about one in 150 U.S. children, a rate that has climbed since the 1980s.
Children are usually diagnosed with autism only after they reach age 2 years or older and Roberts said the hope is that MEG could diagnose children as young as 1 year, so therapy could begin earlier and perhaps be monitored to evaluate the results on the brain.
MEG can cost roughly $400 an hour to perform, but it is harmless and could become less expensive if more devices were available. MEG is used currently to help locate brain tumors and to diagnose epilepsy.
Roberts foresees MEG being employed to examine people with attention deficit disorder and other mental problems.
He said it may also provide researchers with more clues to the causes of autism and help solve the dilemma of what is hereditary and what is environmental about the condition.
(Editing by Jackie Frank)