Modeling extended sources of event-related potentials using anatomical andphysiological constraints

For the study of functional organization and reorganization of the human co rtex by means of electromagnetic source imaging, a measure of the location and spatial extent of neural sources is of interest. This study evaluates t he cortical patch method (CPM), an iterative procedure introduced by Lutken honer et al. [1995] that models EEG/MEG activity by means of extended corti cal patches. Anatomical information is used to constrain estimates of locat ion and extent of neural sources that generate the measured evoked potentia l. Whereas minimum norm approaches use mathematical constraints to solve th e ambiguity of the inverse problem, the CPM introduces constraints based on anatomical and physiological knowledge about neural mass activity. In orde r to test the proposed method, the simulated activity in an artificial sulc us was subjected to the CPM. The results show that even activity on opposin g walls of a sulcus can be well reconstructed. The simulations demonstrate the usefulness and limits of the CPM in estimating the spatial extent of ne ural sources in the cerebral cortex. As an example, an application of the m ethod on experimental somatosensory evoked potentials is presented in the A ppendix. (C) 1999 Wiley-Liss, Inc.