Autistic brains develop more slowly than healthy brains, UCLA researchers say
Imaging study shows slower growth extends into adolescence
By Mark Wheele
(Video by Carlos Mena)
Researchers at UCLA have found a possible explanation for why
autistic children act and think differently than their peers. For the
first time, they've shown that the connections between brain regions
that are important for language and social skills grow much more slowly
in boys with autism than in non-autistic children.
Reporting in the current online edition of the journal Human Brain Mapping, senior author Jennifer
G. Levitt, a professor of psychiatry at the Semel Institute for
Neuroscience and Human Behavior at UCLA; first author Xua Hua, a UCLA
postdoctoral researcher; and colleagues found aberrant growth rates in
areas of the brain implicated in the social impairment, communication
deficits and repetitive behaviors that characterize autism.
Autism is thought to affect one in 110 children in the U.S., and
many experts believe the numbers are growing. Despite its prevalence,
little is known about the disorder, and no cure has been discovered.
Normally, as children grow into teenagers, the brain undergoes major changes. This highly dynamic process depends on the creation of new connections, called white matter, and the elimination, or "pruning,"
of unused brain cells, called gray matter. As a result, our brains
work out the ideal and most efficient ways to understand and respond to
the world around us.
Although most children with autism are diagnosed before they are 3 years old, this new study suggests that delays in brain development continue into adolescence.
"Because the brain of a child with autism develops more slowly
during this critical period of life, these children may have an
especially difficult time struggling to establish personal identity,
develop social interactions and refine emotional skills," Hua said.
"This new knowledge may help to explain some of the symptoms of autism and could improve future treatment options."
The researchers used a type of brain-imaging scan called a T1-weighted MRI, which can map structural changes during brain development.
To study how the brains of boys with autism changed over time, they
scanned 13 boys diagnosed with autism and a control group of seven
non-autistic boys on two separate occasions. The boys ranged in age
from 6 to 14 at the time of the first scan; on average, they were
scanned again approximately three years later.
By scanning the boys twice, the scientists were able to create a
detailed picture of how the brain changes during this critical period of
Besides seeing that the white-matter connections between those
brain regions that are important for language and social skills were
growing much slower in the boys with autism, they found a second
anomaly: In two areas of the brain — the putamen, which is involved in
learning, and the anterior cingulate, which helps regulate both
cognitive and emotional processing — unused cells were not properly
demonstrating differences in brain changes between autistic and non-autistic boys.)
"Together, this creates unusual brain circuits, with cells that are
overly connected to their close neighbors and under-connected to
important cells further away, making it difficult for the brain to process information in a normal way," Hua said.
"The brain regions where growth rates were found to be the most
altered were associated with the problems autistic children most often
struggle with — social impairment, communication deficits and repetitive
behavior," she added.
Future studies using alternative neuroscience techniques should attempt to identify the source of this white-matter impairment, the researchers said.
"This study provides a new understanding of how the brains of children with autism are growing and developing
in a unique way," Levitt said. "Brain imaging could be used to
determine if treatments are successful at addressing the biological
difference. The delayed brain growth in autism may also suggest a
different approach for educational intervention in adolescent and adult
patients, since we now know their brains are wired differently to perceive information."
Other authors on the study included Paul M. Thompson, Alex D. Leow,
Sarah K. Madsen, Rochelle Caplan, Jeffry R. Alger, Joseph O'Neill,
Kishori Joshi, Susan L. Smalley and Arthur W. Toga, all of UCLA. Support
was provided by the National Institutes of Health, the National
Alliance for Autism Research, the National Institute of Mental Health
and the National Institute of Neurological Disorders and Stroke. The
authors report no conflict of interest.
The UCLA Laboratory of Neuro Imaging, which seeks to improve understanding of the brain in health and disease, is a leader in the development
of advanced computational algorithms and scientific approaches for the
comprehensive and quantitative mapping of brain structure and
function. The laboratory is part of the UCLA Department of Neurology, which encompasses more than a dozen research, clinical and teaching programs. The department ranks first among its peers nationwide in National Institutes of Health funding.
on Oct. 22, 2011 at 9:25 PM