NON-FRONTAL P3B-LIKE ACTIVITY EVOKED BY THE WISCONSIN CARD SORTING TEST

EVENT related potentials (ERP) were recorded from 29 electrode positio ns in 10 normal subjects while they performed a simplified version of the Wisconsin Card Sorting Test (WCST). The design focused on ERP diff erences between early and late trials within each WCST series. Topogra phic and dipole analyses confirmed the reliability of two ERP signs: o ne conspicuous mid-parietal P3b wave and one asymmetrical frontal-temp oral component. A three-dipole model accounted for these ERP signs wit h >90% accuracy even in individual subjects, and suggests a sub-second activation of temporal-parietal and medial temporal association areas during card sorting. The WCST-related P3b wave is proposed to reflect working memory operations such as template matching and template form ation during card sorting.