Diffusion tension imaging shows gray matter increase in autistic childrens brains

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CHICAGO, Nov. 28—Scientists using diffusion tension imaging found increased gray matter or mirror neurons that govern social processing and learning by observation, in the brain areas of autistic children, according to research findings presented at the 93rd annual meeting of the Radiological Society of North America (RSNA).

The study was conducted at the Fay J. Lindner Center for Autism, North Shore-Long Island Jewish Health System in Bethpage, N.Y.

"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 Manzar Ashtari, PhD, from the Children's Hospital of Philadelphia in Pennsylvania.

According to Ashtari, 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.

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 fibers. However, Ashtari's team applied it to the assessment of gray matter by employing apparent diffusion coefficient based morphometry (ABM), a new method that highlights brain regions with potential gray matter volume changes. By adding ABM to DTI, the researchers were able to detect subtle regional or localized changes in the gray matter.

According to the results, study participants had enlarged GM volumes (decreased ADC) in the medial frontal gyri, left pre-central gyrus, right post-central gyrus, right fusiform/parahippocampal gyrus, bilateral temporal gyri and bilateral cerebellum. The ASD group had smaller GM volumes in the cerebellum and right amygdala. A separate two-tailed t-test showed no significant differences in the total brain volume of the autism participants as compared with HC.

In addition to the gray matter abnormalities linked to the mirror neuron system, the results revealed that the amount of gray matter in the left parietal area correlated with higher IQs in the control group, but not in the autistic children.

The autistic children also evidenced a significant decrease of gray matter in the right amygdala region that correlated with severity of social impairment. Children with lower gray 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, MD, medical director of the Fay J. Lindner Center for Autism.