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By
Michael Purdy
May
18, 2006 -- A computerized atlas has brought unprecedented
sensitivity to the search for brain structure changes
in a genetic condition known as Williams syndrome, revealing
33 abnormalities in the folding of the brain's surface.
The disorder, which occurs in 1 in every 20,000 births,
impairs visual and spatial skills but preserves musical
ability and sociability.
The
findings, published in The Journal of Neuroscience this
week, suggest the same technique may produce insights
into more common brain development disorders such as
autism, according to the researcher who developed the
brain atlas at Washington University School of Medicine
in St. Louis.
"We
already have a study of autism well along in the pipeline
with colleagues at the University of California-Davis,"
says lead author David Van Essen, Ph.D., the Edison
Professor of Neurobiology and head of the Department
of Anatomy and Neurobiology. "We think that study
will also highlight several previously unrecognized
abnormalities in the folding of the cerebral cortex."
A
more detailed inventory of changes in brain folding
and its connections to changes in cognitive function
should enable researchers to better understand the origins
ofdevelopmental brain disorders and begin devising new
approaches to treat them.
Van
Essen announced the creation of the brain atlas, known
as the Population-Average, Landmark and Surface-based
(PALS) Atlas, in summer 2005, when it was made available
online. PALS is the first atlas that accurately portrays
the complex folds of the cerebral cortex not just from
a single individual but from a group of individuals.
This is important because the folding of cerebral cortex
varies dramatically from one person to the next,similar
to the variability of human fingerprints.
Van
Essen and colleagues from Washington University, Stanford
University and Cedars-Sinai Medical Center in Los Angeles
used data from brain scans of 16 individuals with Williams
syndrome for the study. For the analysis, they aligned
or "registered" each individual brain to the
PALS Atlas. This allowed them to identify 33 changes
in the folds of the cerebral cortex, the surface layer
of the brain credited with many higher cognitive functions.
"We already knew that there are structural abnormalities
in the brains of individuals with Williams syndrome,"
notes Van Essen. "What is interesting and new is
that we found a plethora of changes discernible on a
background of normal variability in folding patterns,
and the fact that the changes are strikingly symmetric."
Scientists
found 16 changes on the left side of the brain and identified
16 changes in corresponding regions on the right side
of the brain. Another abnormality was present only on
the right side of the brain.
Any
one person with Williams syndrome would be unlikely
to have all 33 changes, Van Essen explains, and the
degree of change present can also vary. For example,
they found that the olfactory sulcus, a groove or furrow-like
structure just above the olfactorytract,tendsto be shallower
on average in those with Williams syndrome.
Genetic
and environmental differences, reactions to injury,
and inherited disorders can all change the topography
of the brain in minor and major ways. According to Van
Essen, the new study shows that PALS can help scientists
look beyond such individual variations to quantify brain
structure trends in ways that may provide important
insights. Williams
syndrome results from deletion of genetic material on
a region of chromosome 7,but the size of this deletion
varies across individuals. The new inventory of structural
changes may one day enable scientists to more closely
associate genetic alterations with the development of
different brain structures, or allow them to more precisely
link alterations in specific structures to changes in
cognitive functions.
Although
interventions to alter brain development in Williams
syndrome are likely still a longway off, identifying
the connections between genetic changes, alterations
in brain structure and changes in brain function may
help clinicians and teachers develop customized approaches
to education that allow children with Williams syndrome
to take full advantage of their unique capabilities,
according to Van Essen. (Download image: http://mednews.wustl.edu/asset/page/normal/4294.html)
Van
Essen D, Dierker D, Snyder A, Raichle ME, Reiss A, Korenberg
J. Symmetry of cortical folding abnormalities in Williams
syndrome revealed by surface-based analyses.The Journal
of Neuroscience, May 17, 2006.
Funding
from the National Institutes of Health, the National
Institute of Mental Health, the National Institute for
Biomedical Imaging and Engineering, and the National
Science Foundation supported this research.
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