and language a fraction of a second slower than children without the
disorders, researchers have discovered that measuring magnetic signals
that mark this kind of delayed response has the potential to become a
standardized tool for diagnosing autism.
A child reads instructions on a screen while seated with his head
surrounded by the MEG's noninvasive magnetic detectors.
(Credit: The Children's Hospital of Philadelphia)
"More work needs to be done before this can become a standard tool,
but this pattern of delayed brain response may be refined into the
first imaging biomarker for autism," said Dr. Timothy P.L. Roberts,
vice chairman of Radiology Research at The Children's Hospital of
Philadelphia and head of the study.
As with diagnosing many neurodevelopmental disorders without
biomarkers, psychologists and caregivers use clinical, but still
subjective, judgments to diagnose a range of childhood disorders
affecting as much as 1 percent of U.S. children. Standardized imaging
could help diagnose disorders at an earlier age and differentiate
between disorders across the autism spectrum.
In its study, Roberts' team used magnetoencephalography, or MEG, to
detect magnetic fields in children's brains, much the way
electroencephalography, or EEG, detects electrical fields.
Using a helmet that surrounded each child's head, the team played a
series of recorded beeps, vowels, and sentences. As each child's brain
responds to each sound, noninvasive detectors in the MEG machine
analyzed the brain's changing magnetic fields.
The researchers compared 25 children with ASDs to 17 typically
developing children; the group's mean age was 10. The children with
ASDs responded to sound 11 milliseconds (only about a hundredth of a
second) slower than the control children did. Within the group already
diagnosed with ASDs, the delays were similar regardless of language
impairments.
Roberts said that while an 11-millisecond delay is brief, it suggests
that a child with ASD, on hearing the word "elephant," is still
processing the sound "el" while other children have moved on: "The
delays may cascade as a conversation progresses, and the child may lag
behind typically developing peers."
Roberts added that his team will continue to refine their imaging
techniques in order to determine whether this biomarker is specific to
ASDs, and it will investigate other MEG patterns found in children
with ASDs beyond auditory delays.
The findings, collected at The Children's Hospital of Philadelphia,
are scheduled to appear Friday in the journal Autism Research.