Modeling extended sources of event-related potentials using anatomical and physiological constraints

Abstract

For the study of functional organization and reorganization of the human cortex by means of electromagnetic source imaging, a measure of the location and spatial extent of neural sources is of interest. This study evaluates the cortical patch method (CPM), an iterative procedure introduced by Lü tkenhö ner et al. [1995] that models EEG/MEG activity by means of extended cortical patches. Anatomical information is used to constrain estimates of location and extent of neural sources that generate the measured evoked potential. Whereas minimum norm approaches use mathematical constraints to solve the ambiguity of the inverse problem, the CPM introduces constraints based on anatomical and physiological knowledge about neural mass activity. In order to test the proposed method, the simulated activity in an artificial sulcus was subjected to the CPM. The results show that even activity on opposing walls of a sulcus can be well reconstructed. The simulations demonstrate the usefulness and limits of the CPM in estimating the spatial extent of neural sources in the cerebral cortex. As an example, an application of the method on experimental somatosensory evoked potentials is presented in the Appendix.

Dealing with mismatched fMRI activations in fMRI constrained EEG cortical source imaging: a simulation study assuming various mismatch types

“…For that reason, artificially constructed forward data have been widely used to validate NIP algorithms [23,38]. Hence, in the present simulation study, artificially constructed EEG data assuming realistic conditions were used.…”

“…Since synchronously activated pyramidal cortical neurons, which are oriented perpendicularly on the cortical surface, are widely believed to be the main EEG and MEG generators, many recent studies have adopted this physiological phenomenon as a basic anatomical constraint in EEG or MEG source imaging [3,4,6,8,23]. To impose the anatomical constraint, many dipolar sources were placed on the cortical surface, which had been extracted and tessellated from subjects' structural MRI data.…”

Evaluation of Algorithms for Intracranial EEG (iEEG) Source Imaging of Extended Sources: Feasibility of Using iEEG Source Imaging for Localizing Epileptogenic Zones in Secondary Generalized Epilepsy

“…Because synchronously activated pyramidal cortical neurons, which are located perpendicularly on the cortical surface, are widely believed to be the main EEG and MEG generators, many recent studies have adopted this physiological phenomenon as a basic anatomical constraint in EEG or MEG source imaging (Dale and Sereno 1993;Kincses et al 1999;Dale et al 2000;Babiloni et al 2003Babiloni et al , 2005. To impose this anatomical constraint, numerous dipolar sources were placed on the cortical surface that was tessellated using CURRY6.…”

Spatial resolution of EEG cortical source imaging revealed by localization of retinotopic organization in human primary visual cortex

“…Since synchronously activated pyramidal cortical neurons, which are located perpendicularly on the cortical surface, are widely believed to be the main EEG and MEG generators, many recent studies have adopted this physiological phenomenon as a basic anatomical constraint in EEG or MEG source imaging (Dale and Sereno, 1993;Kincses et al, 1999;Dale et al, 2000;Babiloni et al, 2003Babiloni et al, , 2005. The source imaging with the anatomical constraint, which has been often called cortically distributed source modeling or cortical source imaging, resulted in the elimination of spurious sources (Baillet et al, 1998) as well as the reduction of crosstalk distribution (Liu et al, 1998), compared to conventional volume based imaging techniques.…”