A HIGH-RESOLUTION EEG METHOD BASED ON THE CORRECTION OF THE SURFACE LAPLACIAN ESTIMATE FOR THE SUBJECTS VARIABLE SCALP THICKNESS

To improve the spatial resolution of human event-related potentials, w e developed a new high resolution EEG method based on the improved est imate of the realistic surface Laplacian (SL). The novelty of this met hod consisted in the computation of the local scalp resistance that wa s assumed to be inversely proportional to the local scalp thickness me asured from magnetic resonance images of the subject's head. The local scalp thickness was then multiplied by the SL estimate of the potenti al over a realistic magnetic resonance-constructed model of the subjec t's scalp surface. The new method was applied on human movement-relate d and somatosensory-evoked potentials, the SL estimate at a constant s calp thickness being used as a reference. The locally-predicted scalp thickness was significantly (P < 0.05) higher in the temporal areas (9 .5 +/- 2.6 mm) than in the parieto-occipital (6.6 +/- 1.3 mm) and fron tal (4.8 +/- 1.1 mm) areas. Compared to the SL estimate at constant sc alp thickness, the improved SL estimate enhanced the spatial detail of both movement-related and somatosensory-evoked potentials. (C) 1997 E lsevier Science Ireland Ltd.