A major goal of our research is to investigate the brain mechanisms that underlie linguistic and other cognitive domains. We are involved in comprehensive studies of Williams syndrome, a carefully selected population in which adolescents exhibit a rare fractionation of higher cortical functioning: selective preservation of complex syntax in the face of marked and severe cognitive deficits. The program of studies we have undertaken provides critical evidence bearing on the dissociability of components of language and other cognitive systems. Although it is well known that specific language deficits can exist without an accompanying cognitive deficit, the opposite pattern in which linguistic abilities are selectively spared in the face of overall cognitive deficits is rare and has been little studied. Williams syndrome, a specific neurodevelopmental disorder, may represent a well-defined popUlation in which this pattern of marked cognitive deficits but spared linguistic functioning is observed. This metabolic disorder which results in distinctive physical characteristics (e.g., specific facial features, heart defects) also appears to give rise to a neuropsychological profile which is highly discontinuous from normal. We address the issue of the nature of the neural substrate that supports the unusual neuropsychological functioning found in Williams syndrome. The intensive evaluation of cognitive and linguistic capacities of such a homogeneous population of individuals affords an important opportunity to explore the interrelationships of cognitive domains and their underlying neural substrates.