II. Hypersociability in Williams Syndrome

Studies in animals have implicated the amygdala in emotional and social behaviours, especially those related to fear and aggression. Although lesion and functional imaging studies in humans have demonstrated the amygdala's participation in recognizing emotional facial expressions, its role in human social behaviour has remained unclear. We report here our investigation into the hypothesis that the human amygdala is required for accurate social judgments of other individuals on the basis of their facial appearance. We asked three subjects with complete bilateral amygdala damage to judge faces of unfamiliar people with respect to two attributes important in real-life social encounters: approachability and trustworthiness. All three subjects judged unfamiliar individuals to be more approachable and more trustworthy than did control subjects. The impairment was most striking for faces to which normal subjects assign the most negative ratings: unapproachable and untrustworthy looking individuals. Additional investigations revealed that the impairment does not extend to judging verbal descriptions of people. The amygdala appears to be an important component of the neural systems that help retrieve socially relevant knowledge on the basis of facial appearance.

Williams syndrome (WS) is a developmental disorder affecting connective tissue and the central nervous system. A common feature of WS, supravalvular aortic stenosis, is also a distinct autosomal dominant disorder caused by mutations in the elastin gene. In this study, we identified hemizygosity at the elastin locus using genetic analyses in four familial and five sporadic cases of WS. Fluorescent in situ hybridization and quantitative Southern analyses confirmed these findings, demonstrating inherited and de novo deletions of the elastin gene. These data indicate that deletions involving one elastin allele cause WS and implicate elastin hemizygosity in the pathogenesis of the disease.

The natural history of Williams syndrome, including medical complications, growth patterns, and problems in adulthood, was investigated. A growth pattern characterized by delay in the first 4 years of life, catch-up growth in childhood, and low ultimate adult height was found. Despite multiple medical problems in infancy, including feeding problems, failure to thrive, colic, and otitis media, mean age at diagnosis was 6.4 years. Developmental disabilities and cardiovascular disease were the major concerns in childhood. The older children developed progressive joint limitation and hypertonia. Adult patients were handicapped by their developmental disabilities. Hypertension, and gastrointestinal and genitourinary problems occurred frequently. Independent living and competitive employment were limited less by the individual's physical problems than by the psychologic and adaptive limitations. Williams syndrome is a progressive disorder with multisystem involvement.