FUNCTIONAL BRAIN IMAGING - DIPOLE LOCALIZATION AND LAPLACIAN METHODS

The performance of two methods, used to localize brain activity from e voked potential fields measured on the scalp, was assessed in a tank m odel of the human head. This physical model contained a human skull en cased in a polymer simulating the resistivity and geometry of brain an d scalp. The dipole localization method mislocalized the positions of known dipole sources by several centimeters. The mislocalization was s ystematic. The dipoles were localized too deeply in the head. The Lapl acian method yielded a field resembling the brain surface field (epico rtical potential field) provided that the iso-potential contours of th e scalp field closed within the measurement range. Clipping resulted i n a serious mislocalization of the position of the peak of the epicort ical potential field.