Study Discovers Link Between Increased White Matter In The Brain And Poor Motor Skills In Children With Autism

A study published in the
August issue of the journal Brain demonstrates, for the first time, an
association between increased white matter volume and functional impairment
in children with autism. Findings from researchers at the Kennedy Krieger
Institute in Baltimore, Md., reveal that in children with autism, increased
white matter volume in the motor region of the brain predicts poorer motor
skills. Conversely, in typically developing children, increased white
matter volume predicts improved motor skills, with a similar association
observed in children with attention deficit/hyperactivity disorder (ADHD).
The relationship between increased white matter volume and functional
impairment, which appears to be specific to autism, may be representative
of global patterns of brain abnormality in autism that not only contribute
to motor dysfunction, but also to deficits in socialization and
communication that define the disorder.



Children with autism are typically motorically clumsy and awkward,
similar to how they are socially clumsy and awkward. They often experience
difficulties with basic motor control and with learning more complex motor
skills, such as riding a tricycle, pumping their legs on a swing or
buttoning, zipping and tying shoe laces. Additionally, high-functioning
children with autism often excel in academic areas, such as math, as
opposed to athletic activities, such as baseball. Because measures of motor
function are highly quantifiable and reproducible, they are much easier to
study than measures of social and communication behavior. Motor signs can
serve as markers for deficits in parallel brain systems important for
control of socialization and communication.



Researchers utilized anatomic magnetic resonance imaging (aMRI)
measures to study 76 children ages 8-12 years, including: 20
high-functioning children with autism; a control group of 36 typically
developing (TD) children; and a clinical control group of 20 children with
ADHD, a developmental disorder which, like autism, has been found to be
associated with impairments in motor execution and control. Findings show a
robust association between increased white matter volume and basic motor
skill impairment in children with autism, which suggests that it may be a
defining biological feature of the disorder. Results demonstrate that the
association of increasing white matter volume and poor motor function
appears to be specific to autism, as this association was not observed in
the TD or ADHD groups.



"Carefully examining systems responsible for controlling simple aspects
of behavior, such as basic motor control, can provide a window into
understanding the systems that are responsible for control of more complex
social and communicative behavior," said Dr. Stewart H. Mostofsky, lead
study author and a pediatric neurologist in the Department of Developmental
Cognitive Neurology at the Kennedy Krieger Institute. "This finding is an
important step forward and will guide future research into the
abnormalities associated with socialization and communication that define
the disorder."
















Motor impairments, such as those seen in autism, offer valuable insight
into the neurologic basis of developmental disorders. This is especially
critical for autism and other disorders where the neurologic basis is not
well understood. The most consistent neuroimaging finding in children with
autism is increased brain volume, which has been primarily attributed to an
increased volume of white matter (white matter consists of the connections
between brain regions). To address the current lack of evidence showing
that increases in white matter volume are associated with functional
impairment in children with autism, researchers in this study examined
associations between motor skills and white matter volume.



Researchers assessed participants' basic motor skills using a
standardized motor examination for children, the Physical and Neurologic
Examination of Subtle Signs (PANESS), which has been used in past studies
to demonstrate basic motor skill impairments in children with autism and
ADHD. With the PANESS, higher scores indicate poorer performance.
Consistent with previous findings, children with autism had significantly
poorer motor performance (higher PANESS scores) than TD controls.
Researchers identified a strong positive correlation between total PANESS
score and white matter volume, revealing that increased white matter volume
predicted poorer motor skills in these children.



In contrast to the children with autism, TD children showed a
significant correlation in the opposite direction, with increased white
matter volume predicting better motor skills (lower PANESS scores). The
correlation in children with ADHD was considerably different from the
children with autism and similar to the TD group.



In the future, Dr. Mostofsky and his colleagues hope to examine
correlations of brain structure with motor performance using imaging
techniques, such as diffusion tensor imaging (DTI), which can provide
additional information about white matter connections. Upcoming studies may
also extend this research to younger children and investigate, from a
developmental perspective, what contributes to impaired acquisition and
learning of motor skills in children with autism. Additionally, the brain
systems involved in motor skill learning appear to be important for
learning aspects of socialization and communication, including language.
Future research that examines how these learning systems are affected in
children with autism could therefore provide crucial information about the
brain basis of the disorder and prove very valuable in guiding, and
ultimately improving, therapy.



About Autism



Autism spectrum disorders (ASD) is the nation's fastest growing
developmental disorder, with current incidence rates estimated at 1 in 150
children. This year more children will be diagnosed with autism than AIDS,
diabetes and cancer combined, yet profound gaps remain in our understanding
of both the causes and cures of the disorder. Continued research and
education about developmental disruptions in individuals with ASD is
crucial, as early detection and intervention can lead to improved outcomes
in individuals with ASD.



About the Kennedy Krieger Institute



Internationally recognized for improving the lives of children and
adolescents with disorders and injuries of the brain and spinal cord, the
Kennedy Krieger Institute in Baltimore, Md., serves more than 13,000
individuals each year through inpatient and outpatient clinics, home and
community services and school-based programs. Kennedy Krieger provides a
wide range of services for children with developmental concerns mild to
severe, and is home to a team of investigators who are contributing to the
understanding of how disorders develop while pioneering new interventions
and earlier diagnosis. For more information on Kennedy Krieger Institute,
visit kennedykrieger.


Kennedy Krieger Institute

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