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.
Citation:
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
