Thursday, August 19, 2010

EYE MOVEMENT TESTS IDENTIFY BRAIN ABNORMALITIES IN FAMILY MEMBERS OF INDIVIDUALS WITH AUTISM


Researchers at the University of Illinois at Chicago report that first-degree relatives of individuals with autism have abnormal eye movements similar to some individuals with autism, suggesting that these alterations within sensorimotor and cognitive brain circuitry may be familial traits.

The study is published in the August issue of Archives of General Psychiatry.

Autism, a lifelong disorder with few known causes, is hereditary but has considerable genetic and behavioral variation. People with autism often have social and communication impairments, behavioral inflexibility, and difficulty controlling or regulating behavior.

Researchers at UIC conducted eye movement tests and other assessments of neurobehavioral function in 57 first-degree relatives of individuals with autism. They compared the results with 40 healthy matched controls that did not have a family member with autism.

The tasks assessed saccades, or rapid eye movements that shift gaze between objects in the field of vision, and smooth-pursuit eye movements, which stabilize gaze on slowly moving objects. The researchers found that family members of individuals with autism performed less accurately when making saccades, made slower smooth pursuit eye movements, and had difficulty inhibiting reflexive saccades.

“We found different parts of the brain controlling different types of eye movements,” said John Sweeney, senior author of the study, professor and director of the Center for Cognitive Medicine in the UIC department of psychiatry. “Some family members had problems in the cerebellum, some had problems in the prefrontal cortex, and some had a problem in how the frontal and parietal cortex was interacting.”

The abnormalities, associated with several brain pathways, have been linked to autism and are important for language skills, motor control and the regulation of behavior.

“The different types of brain system abnormalities in different people allows us also to think that we might be able to tease out heterogeneity within the broad spectrum of autism in a way that could narrow groups down enough to be able to track genetic and other causes of illness in subgroups with the disorder,” Sweeney said.

The findings may provide researchers insight about which brain system and/or gene abnormalities increase the likelihood that someone is going to develop autism, or perhaps, have a child with autism.

“It's really a way for us to understand potential risk mechanisms for clinical practice. It also gives us a potential objective laboratory test to evaluate how new treatments are affecting brain function,” Sweeney said. “It opens up a window for us to tackle some really big, unanswered questions in autism.”

The researchers also found that family members had executive dysfunction on neuropsychological tests, including a reduced ability to recall visual-spatial sequences. Communication abnormalities and increased rates of obsessive and compulsive behaviors also were observed.

University of Illinois at Chicago

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