The Salk Institute's Laboratory for Cognitive Neuroscience examines how the brain is organized in normal individuals, as well as individuals afflicted with a variety of brain disorders, including autism, Down syndrome, and Williams syndrome – the latter is a genetic disorder that affects one in approximately 20,000 births. Genetic work has demonstrated that Williams syndrome is associated with the deletion of a specific part of the human chromosome 7. Children affected by it share a variety of physical traits, including heart defects and a distinct set of facial abnormalities.
Most are never capable of living independently, but they possess extremely well developed language skills. One patient who typifies the syndrome is an 18-year-old girl who cannot tie her shoes, but possesses a rich vocabulary and an affinity for vivid oral story telling. They are also extraordinarily social.
Salk researchers have developed a battery of tests that measure cognitive abilities according to specific and discreet domains. These assays include language processing tests and tests of spatial abilities. By comparing test results from Williams syndrome children and children with Down syndrome, Salk researchers have shown that specific differences exist between these groups. The Down syndrome children perform relatively well in tests of spatial ability but poorly in language skills, whereas the Williams syndrome children have the opposite profile.
Ideally, researchers would like to pinpoint the differences in brain structure that are responsible for the different abilities. Toward this goal, Institute scientists are developing a bioimaging facility. This facility is devoted to producing computerized three-dimensional images of subjects' brains from two-dimensional MRI (magnetic resonance imaging) data. The computer allows researchers to manipulate the images, and to isolate and compare the brains of normal children and children with cognitive disorders. This technique allows researchers to identify brain regions that are associated with specific functions and abilities – in short, to correlate brain structure and behavior.
In collaboration with other research groups, Salk scientists have found structural comparisons between autistic children and Williams syndrome children. In marked contrast to Williams syndrome children, autistic children often excel at spatial tests, such as using blocks to reproduce a pattern, but typically lack developed language skills and are markedly unsociable.
The Laboratory for Cognitive Neuroscience maintains close ties with the families of Williams syndrome children. Many of the children come from all over the country on an annual basis to undergo testing at the Salk Institute. Maintaining a close ongoing relationship in this manner allows families to benefit in an immediate way from the results of research.
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Ursula Bellugi, professor and director of the Salk Laboratory for Cognitive Neuroscience, is heading a multi-institutional team that has been awarded a $5.5 million program project grant by the National Institute of Child Health and Human Development (NICHD) to link social behavior to its underlying neurobiological and molecular genetic basis, using Williams syndrome as a model.
"How the brain processes social information and integrates it with other forms of perception and learning is one of the major frontiers in neuroscience," says Bellugi. "Using Williams syndrome as the basis for a new approach to social neuroscience is exciting and promising, in part because its genetic basis is clearly understood, and it is associated with a very specific pattern of cognitive strengths and weaknesses and some puzzling paradoxes."
The current grant is the latest chapter in a unique and exceptionally successful scientific alliance. Led by Bellugi, a team of researchers that includes Salk scientists Fred Gage and Terry Sejnowski and collaborators at UC San Diego and the University of Utah, working in such disparate fields as social cognition, stem cell biology, neuronal architecture and neuroimaging, are looking to Williams syndrome to provide clues to some of the mysteries of the genetic basis of social behavior.
Williams syndrome arises from a faulty recombination event during the development of sperm or egg cells. To children with Williams syndrome, people are much more comprehensible than inanimate objects. Despite myriad health problems and generally low IQs, they are extremely gregarious, irresistibly drawn to strangers and insist on making eye contact. They are confounded by the visual world around them, however: when asked to draw a bicycle, they will show all the parts but strew them randomly across the page. It is this strange mix of mental peaks and valleys that Bellugi and her collaborators hope will allow them to untangle the connections between genes and social behavior.
"Understanding the mechanisms and pathways underlying the organization of human social behavior is important in a wide variety of mental disorders," Bellugi says. "By dissecting Williams syndrome, we hope to gain new insight into other neurodevelopmental disorders such as autism."