## EEG/MEG Source Analysis Based on Realistic Finite Element Volume Conductor Modeling and its Application in Presurgical Epilepsy Diagnosis and in the Field of Evoked Responses

Bioelectric source reconstruction in the human brain from scalp Electro- and Magneto- encephalography (EEG/MEG) signals is sensitive to head volume conductor properties, i.e., tissue geometries and conductivities. A mathematical dipole is widely used as the model of the primary current source. Since the inverse problem is not uniquely solvable, different classes of approaches exist and will be presented, which are based on different a-priori knowledge. All inverse methods are based on solutions to the corresponding forward problem, i.e., the simulation of the electric potential and the magnetic flux at the head surface for a dipole in the cortex sheet of the human brain.

In my talk, I will propose different approaches to model the dipole singularity introduced into the differential equation within the finite element (FE) method based solution to the EEG/MEG forward problem. The presented approaches will be validated using high-resolution constrained Delaunay tetrahedralizations and geometry-adapted hexahedral meshes in a multi-layer anisotropic sphere model. Methods are discussed to individually estimate the head tissue conductivity parameters. A successful application of the presented approaches to the fields of presurgical epilepsy diagnosis and evoked responses will finally be discussed.