Electrophysiological correlates of cognitive functions activated during Wisconsin Card Sorting Test

WCST (Wisconsin Card Sorting Test) is one of the most commonly used neuropsychological tests for measuring the function of prefrontal cortex. The research so far has pointed that the neural activity, connected to the early attempts in the series, during which the card sorting, i.e. redistributing attention towards the new relevant category, is different in relation to the neural activity connected with the late attempts during which the subject maintains the efficient rule of card sorting. The amplitude of the P3b component is lower with early sorting attempts, and it gradually increases with the number of attempts within the same category, which probably reflects working memory processes. Research using functional magnetic resonance imaging (fMRI), as well as ERP research, is questioning the efficacy and validity of WCTS as test that measures the functions of the frontal lobe, because during the test, other brain regions are also activated, for example left occipital cortex and cerebellum. In this research, we have observed neurophysiological correlates of cognitive functions during WCST performance. 20 adult subjects, aged between 20 and 30 years (10 female and 10 male subjects) took part in this study. ERP method and NeuroScan programme were used. Evoked brain potentials were recorded during the performance of the computerized version of this test. To examine brain activity related to frontal functions, we have averaged ERP time windows. We have then compared ERP correlates of cognitive processes related to receiving negative feedback information after which the correct sorting answer ensued, and ERP correlates related to receiving positive feedback information during early attempts in the series. We have assumed that negative feedback information signals the subject to change the sorting rule and the subject decides according to which category will the card be sorted, whereas positive feedback information signals that the established sorting rule should be retained. The results confirm a larger amplitude of frontally distributed P300 component with negative feedback information in relation to positive feedback information. The differences regarding sex of the subjects have not been confirmed. On the basis of our results, we have concluded that WCTS measures the activation of prefrontal cortex and that there are differences in neural activity when considering feedback information type.