REPRODUCIBILITY AND VALIDITY OF ELECTRIC SOURCE LOCALIZATION WITH HIGH-RESOLUTION ELECTROENCEPHALOGRAPHY

The present study investigates the reproducibility and validity of the EEG source localisation of somatosensory evoked potentials (SEPs) usi ng high-resolution EEG (61 scalp electrodes) and a source reconstructi on on the basis of the individual brain morphology as obtained from ma gnetic resonance images (MRIs). The somatosensory evoked potentials (S EPs) to electrical stimulation of the right median nerve were repeated ly collected from the scalp of one healthy subject in 9 replications r un on 9 different days. The source reconstruction for the 19 ms SEP co mponent was performed by using a single moving dipole model as a sourc e model. Two different head models were used: a spherical 3 shell mode l and a more realistically shaped 3 compartment model computed using t he boundary element method (BEM). The source locations of the 19 ms SE P component were found to be highly reproducible using both head model s: the mean standard deviation of the dipole locations was found to be 2.6 mm for the 3 shell model and 4 mm for the more realistically shap ed head model. By projection into the individual MRI, the dipoles resu lting from either head models were found to be located within the post central gyrus. The electric source locations were consistent with the maximum of the task-specific changes seen in a functional magnetic res onance imaging (fMRI) experiment when using the same somatosensory sti mulation protocol. (C) 1997 Elsevier Science Ireland Ltd.