Brain imaging of autistic children shows malfunctioning grey matter
10 January 2008 A novel imaging technique has been used to discover
malfunctioning grey matter in autistic children in the brain areas that
govern social processing and learning by observation.
Results of the study conducted at the Fay J Lindner Center for Autism,
North Shore-Long Island Jewish Health System in Bethpage, NY, were presented
at the annual meeting of the Radiological Society of North America (RSNA) in
November. "Our findings suggest that the inability of autistic children to
relate to people and life situations in an ordinary way may be the result of
an abnormally functioning mirror neuron system," said lead author Dr Manzar
Ashtari, from the Children's Hospital of Philadelphia in Pennsylvania.
Mirror neurons are brain cells that are active both when an individual is
performing an action and experiencing an emotion or sensation, and when that
individual witnesses the same actions, emotions and sensations in others.
First observed in the macaque monkey, researchers have found evidence of
a similar system in humans that facilitates such functions as learning by
seeing as well as doing, along with empathizing and understanding the
intentions of others. Dr. Ashtari's study found the autistic children had
increased grey matter in brain regions of the parietal lobes implicated in
the mirror neuron system. The study included 13 male patients diagnosed
with high-functioning autism or Asperger syndrome and an IQ greater than 70
and 12 healthy control adolescents. Average age of the participants was
about 11 years. Each of the patients underwent diffusion tensor imaging
(DTI), a technique that tracks the movement of water molecules in the brain.
DTI is traditionally used to study the brain's white matter, as well as the
brain fibres. However, Dr Ashtari's team applied it to the assessment of
grey matter by employing apparent diffusion coefficient based morphometry
(ABM), a new method that highlights brain regions with potential grey matter
volume changes. By adding ABM to DTI, the researchers can detect subtle
regional or localized changes in the grey matter. In addition to the grey
matter abnormalities linked to the mirror neuron system, the results of this
study revealed that the amount of grey matter in the left parietal area
correlated with higher IQs in the control group, but not in the autistic
children. "In the normal brain, larger amounts of grey matter are
associated with higher IQs," Dr Ashtari said. "But in the autistic brain,
increased grey matter does not correspond to IQ, because this grey matter is
not functioning properly." The autistic children also evidenced a
significant decrease of grey matter in the right amygdala region that
correlated with severity of social impairment. Children with lower grey
matter volumes in this area of the brain had lower scores on reciprocity and
social interaction measures. "Impairments in these areas are the hallmark
of autism spectrum disorders, and this finding may lead to greater
understanding of the neurobiological underpinnings of the core features of
autism," said study co-author Joel Bregman, M.D., medical director of the
Fay J. Lindner Center for Autism. Autism is the fastest growing
developmental disability in the United States and typically appears during
the first three years of life. Children with autism are hindered in the
areas of social interaction and communication skills. According to the
Centers for Disease Control and Prevention, as many as 1.5 million Americans
have autism.
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