Saturday, February 8, 2014

BMC Medicine: Autism and Aspergers are Different on EEG

Autism and Asperger’s are different… at least on EEG by Nancy Fliesler on August 15, 2013
The Asperger’s difference
In the new study, published July 31 in the open-access journal BMC Medicine, Duffy compared these two groups with an additional 26 children meeting behavioral criteria for Asperger’s.
Using 40 coherence factors, Duffy’s algorithm classified 25 of the 26—96 percent—as belonging to the autism sample. So clearly, the children with Asperger’s were closer to the autism profile than to the neurotypical controls. However, further coherence analysis correctly classified 24 of the 26 children—92 percent—as having clinical Asperger’s syndrome as distinct from ASDs. These classifications held up on repeated analyses.
What was different in the Asperger’s group? Duffy zeroed in on four EEG coherence factors (Factors 3, 15, 33 and 40) that best distinguished them from the group with ASDs. This graphic illustrates the differences in brain connectivity; imagine you’re looking down at the brain from above (see the nose at the top of each “head”):

The red and black dots indicate electrodes. Red lines between the dots indicate increased coherence between pairs of signals in the Asperger’s group, and blue-green lines indicate decreased coherence in the Asperger’s group.
So what does this mean?
Duffy hypothesizes that Factor 15, indicating reduced connectivity in the arcuate fasciculus, a brain structure involved in language, indicates a language deficiency, but that the Asperger’s brain compensates for this with increased connectivity in the left temporal region (Factor 3), allowing children to acquire language skills.
“Children with Asperger’s have very unique aspects to their language,” says Duffy. “The difference in coherence may account for their more stylized, literal use of language.”
As for Factors 33 and 40, which each show reduced coherence values in the Asperger’s group, Duffy proposes that they correspond to differences in visual-spatial functioning and in right-hemisphere areas thought to be involved in perceiving social and language nuance.

All this, of course, invites further investigation. Duffy is planning another study using coherence factors to distinguish children with autism from those with global developmental delay, which can often look like autism. With a larger sample size, he hopes to investigate whether there are differences between Asperger’s syndrome and high-functioning autism.
But in the meantime, since EEGs are relatively cheap diagnostic tools, Duffy feels they could eventually be developed to provide a diagnostic tool for autism in settings where there aren’t enough skilled behavioral clinicians, such as developing countries and certain underserved parts of the U.S.
“With some public and private support, I believe this could potentially be translated into a practical tool within my lifetime,” he says.

Duffy FH, Shankardass A, McAnulty GB, & Als H (2013). The relationship of Asperger’s syndrome to autism: a preliminary EEG coherence study. BMC medicine, 11 PMID: 23902729

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