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Imaging studies clarify brain changes
associated with language deficits in autism
Differences in left/right dominance
associated with language problems only
BOSTON - October 11, 2004 - Researchers at Massachusetts
General Hospital (MGH) have found that a structural difference previously
observed in the brains of some boys with autism is found primarily
in those with language problems and also appears in boys with a
condition called specific language impairment (SLI). The findings
suggest that this anatomic feature may underlie language difficulty
only rather than overall autism and supports an apparent relationship
between the two conditions. Appearing in the an upcoming issue of
Annals of Neurology, the study is now
available online.
"This study further strengthens the biological basis of the
language problems seen in both autism and SLI," says Gordon
Harris, PhD, director of the Radiology Computer-Aided Diagnostics
Laboratory (RAD CADx Lab) in the MGH Department of Radiology, the
paper's senior author.
Autism is a serious developmental disorder characterized by a lack
of normal social interaction, language abnormalities and repetitive,
ritualistic behavior. In previous imaging studies of autistic boys,
Harris's group identified an alteration in language-associated areas
of the brain. In most right-handed individuals, what is referred
to as Broca's area is larger on the left side of the brain. The
2002 MGH study showed that most right-handed autistic boys had a
reversal of this pattern, with the larger area on the right side.
Other researchers have reported similar reversal of the normal brain
asymmetry in people with SLI, a condition of delayed language development
without other impairments, and in other language disorders. A genetic
connection may exist between SLI and autism, since relatives of
those with one disorder have an increased risk of developing the
other. Because their earlier study did not distinguish between autistic
boys with and without language problems, the MGH team looked more
closely at whether the altered brain asymmetry might be related
to language difficulties specifically, or to autism in general.
The study enrolled 16 boys with autism, six of whom had normal language
development; 9 boys with SLI; and 11 without any developmental disabilities.
As in the earlier study, only boys participated because autism predominantly
affects males. The boys were ages 6 through 13 and were all right-handed.
Detailed magnetic resonance imaging (MRI) studies were taken of
participants' brains, and the data was analyzed using advanced techniques
that provide detailed information about specific anatomical regions.
The images showed that the reversal of the normal left/right asymmetry
of language-associated brain structures was strongly associated
with language impairment but not necessarily with autism. In both
the participants with SLI and the autistic boys with language problems,
Broca's area was larger on the right side. The right side was largest
in those with the most serious impairments. In the autistic boys
with normal language development, Broca's area was larger on the
left, as was seen in normal controls.
"There seem to be clear differences in developmental neuroanatomy
in both these disorders," says Harris. "In boys with normal
language skills, handedness and language tend to be dominant in
the same hemisphere, but for those with language impairment, there
appears to be a split. A key question to pursue is whether the language
dominance dichotomy results from the language impairments or whether
development of these characteristics in opposing hemispheres leads
to language disorganization." Harris adds that future studies
should look into whether these findings are also seen in autistic
adults and, if enough participants can be enrolled, in females with
autism. He is an assistant professor of Radiology at Harvard Medical
School.
The report's co-authors are first author Lies De Fosse of the MGH
RAD CADx Lab and Center for Morphometric Analysis; Steven Hodge,
Nikos Makris, MD, PhD, David Kennedy, PhD, Verne Caviness, MD, DPhil,
David Ziegler, and Martha Herbert, MD, PhD, of MGH; Lauren McGrath,
Shelley Steele, and Helen Tager-Flusberg, PhD, Boston University
Medical Center; and Jean Frazier, MD, McLean Hospital. The research
was supported by grants from the National Institutes of Health.
Massachusetts General Hospital, established in 1811, is the original
and largest teaching hospital of Harvard Medical School. The MGH
conducts the largest hospital-based research program in the United
States, with an annual research budget of more than $400 million
and major research centers in AIDS, cardiovascular research, cancer,
cutaneous biology, medical imaging, neurodegenerative disorders,
transplantation biology and photomedicine. In 1994, MGH and Brigham
and Women's Hospital joined to form Partners HealthCare System,
an integrated health care delivery system comprising the two academic
medical centers, specialty and community hospitals, a network of
physician groups, and nonacute and home health services.
Media Contact: Sue
McGreevey , MGH Public Affairs
Physician Referral Service: 1-800-388-4644
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