PHYSIOLOGICAL ACTIVATION OF A CORTICAL NETWORK DURING PERFORMANCE OF THE WISCONSIN CARD SORTING TEST - A POSITRON EMISSION TOMOGRAPHY STUDY

To determine the neural circuitry engaged by performance of the Wiscon sin Card Sorting Test (WCST), a neuropsychological test traditionally considered to be sensitive to prefrontal lesions, regional cerebral bl ood flow was measured with oxygen-15 water and positron emission tomog raphy (PET) while young normal subjects performed the test as well as while they performed a specially designed sensorimotor control task. T o consider which of the various cognitive operations and other experie ntial phenomena involved in the WCST PET scan are critical for the pat tern of physiological activation and to focus on the working memory co mponent of the test, repeat WCST scans were also performed on nine of the subjects after instruction on the test and practice to criteria. W e confirmed that performance of the WCST engages the frontal cortex an d also produces activation of a complex network of regions consistentl y including the inferior parietal lobule but also involving the visual association and inferior temporal cortices as well as portions of the cerebellum. The WCST activation in the dorsolateral prefrontal cortex (DLPFC) remained significant even after training and practice on the test, suggesting that working memory may be largely responsible for th e physiological response in DLPFC during the WCST and, conversely, tha t the DLPFC plays a major role in modulating working memory.