Autistic Children May Have Abnormal Functioning Of Mirror Neuron System

ScienceDaily (Nov. 28, 2007) — Using a novel imaging technique to study autistic children, researchers have found increased gray matter in the brain areas that govern social processing and learning by observation.

"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, Ph.D., 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 gray 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 fibers. However, Dr. 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 can detect subtle regional or localized changes in the gray matter.

In addition to the gray matter abnormalities linked to the mirror neuron system, the results of this study 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.

"In the normal brain, larger amounts of gray matter are associated with higher IQs," Dr. Ashtari said. "But in the autistic brain, increased gray matter does not correspond to IQ, because this gray matter is not functioning properly."

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, 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.

Results of the study conducted at the Fay J. Lindner Center for Autism, North Shore-Long Island Jewish Health System in Bethpage, N.Y., were presented November 28 at the annual meeting of the Radiological Society of North America.

Co-authors are S. Nichols, Ph.D., C. McIlree, M.S., L. Spritzer, B.S., A. Adesman, M.D., and B. Ardekani, Ph.D.

This study was supported by The Feinstein Institute for Medical Research, North Shore-Long Island Jewish Health System and the National Center for Research Resources/National Institutes of Health.

This imbalance may make it tougher for them to function socially, study suggests

WEDNESDAY, Nov. 28 (HealthDay News) -- Children diagnosed with autism have more gray matter in their brains than healthy children, report researchers who used a novel imaging technique to analyze brain structure.

The excess gray matter in the parietal region may make it harder for autistic children to learn how to function socially by watching other people's behaviors, the researchers suggest. In contrast, increased gray matter among healthy children correlated with higher IQ, the researchers said.

The researchers, at the Fay J. Lindner Center for Autism, North Shore-Long Island Jewish Health System in Bethpage, N.Y., were to present their findings Nov. 28 at the Radiological Society of North America annual meeting, in Chicago.

The researchers analyzed the brain images of 13 males who had either high-functioning autism or Asperger Syndrome, a developmental disorder in the autism spectrum. The researchers compared the results with images from 12 healthy children who did not have autism. On average, the preteens were 11 years old.

The researchers used a technology called diffusion tensor imaging (DTI) to produce a visual map of each child's brain. Scientists usually use DTI to visualize the brain's white matter, as well as the brain fibers. However, the research 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.

They found gray matter abnormalities throughout the brain, but particularly in the parietal lobe, which adds to previous research suggesting that mirror neurons found in that region play a key role in autism.

The increase in gray matter probably affects the action of the mirror neurons, said study investigator Manzar Ashtari, who is now a senior neuroscientist at Children's Hospital of Philadelphia. Mirror neurons are those cells that activate when you perform an action and then see someone else perform the same action, or vice versa. These neurons have been dubbed the "monkey-see, monkey-do" cells.

"Mirror neurons allow us to learn without knowing we are learning and then respond appropriately in certain situations," said Ashtari. She hopes to explore the link between autism and mirror neurons in future studies, using brain imaging techniques to find out when, and if, mirror neurons are engaged at the appropriate times.

The challenge with imaging studies is getting beyond measures of volume to understand smaller and more localized changes, Ashtari said. Adding ABM to DTI gave the study researchers the ability to detect subtle regional or localized changes in the gray matter, which was not possible before, she said.

The brain structures of people with autism change over their life span, explained Ashtari, which poses a problem for researchers trying to understand the disorder. "I believe it's a very complex process the brain goes through with autism and we don't know much" about that process, she said.

Unfortunately, this new imaging technique can't be used to diagnose autism, Ashtari cautioned.

"Everyone is trying to find something that is very robust, to be able to say 'you take this test, do this screening, and then you know,'" she said.

Dr. Stewart H. Mostofsky is a pediatric neurologist at the Kennedy Krieger Institute in Baltimore. He agreed that it is too soon to use any imaging technique as a part of diagnosing autism.

"We are dealing with a disorder that is defined by symptoms," said Mostofsky, who was not involved in the study. He added that there are many different possible causes of autism, which means many different brain abnormalities. "The question beyond that is whether there is a common neuromechanism. That is not entirely clear. There is no evidence that would support imaging as a diagnostic tool."

Further, he cautioned that the new study had a very small number of high-functioning participants, so conclusions about brain abnormalities cannot be generalized to all people with autism.

Dr. Vilayanur S. Ramachandran, professor of psychology and director of the Center for Brain and Cognition at the University of California, San Diego, called the new research "a landmark anatomical study which lends support to the increasing evidence that mirror neurons are an underlying cause of autism." He said the finding of excess gray matter suggests that one of the issues with the autistic brain may be a matter of malfunctioning connections between neurons, rather than the neurons themselves.

Ramachandran and his colleagues published work earlier this year in the journal Cognitive Brain Research that suggested that autistic children have a faulty mirror neuron system.

In February, the U.S. Centers for Disease Control and Prevention released statistics indicating that one in every 150 American 8-year-olds has autism spectrum disorders. A decade ago, estimates ranged anywhere from one in 500 youngsters to one in 166.

But those new statistics -- from a 14-state survey conducted by the CDC -- failed to clear up the mystery of why autism might be striking more and more children with each passing year.

To learn more about autism, visit the U.S. National Institute of Mental Health.

SOURCES: Manzar Ashtari, Ph.D., senior neuroscientist at Children's Hospital of Philadelphia; Vilayanur S. Ramachandran, M.D., Ph.D., professor of psychology and director of the Center for Brain and Cognition, University of California, San Diego, La Jolla; Stewart H. Mostofsky, M.D., pediatric neurologist, the Kennedy Krieger Institute, Baltimore; Nov. 28, 2007, presentation, Radiological Society of North America