Skull Conductivity Estimation for EEG Source Localization

Abstract

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. Abstract-A reliable leadfield matrix is needed to solve the magnetoencephalography/electroencephalography (M/EEG) source localization problem. The computation of this matrix requires several physical parameters, including the conductivity of the tissues that compose the subject's head. Since it is not precisely known, we modify a recent Bayesian algorithm to estimate the skull conductivity jointly with the brain activity directly from the M/EEG measurements. Synthetic and real data are used to compare our technique with two optimization algorithms, showing that the proposed method is able to provide results of similar or better quality with the advantage of being applicable in a more general case.

Fast Approximation of EEG Forward Problem and Application to Tissue Conductivity Estimation

“…We then compare the approximation error (7) in Fig. 3a with its upper bound error, computed with (10). Fig.…”

“…We now express problem (10) as a simple least squares problem. Using the linear decomposition of H σ as a sum of conductivity-independent matrices (3), we get:…”

“…Taking account of the composite structure of the human skull could improve the accuracy of EEG source analysis [9]: in such a case, conductivity of each skull tissue should be estimated independently. A possible solution is to estimate tissue conductivities and cortical activity simultaneously [10]- [13]. Doing this requires to solve the EEG forward problem for possibly many different conductivity configurations.…”

“…Our method is inspired by the reduced basis method, but adapted to the particular structure of the EEG forward problem and the nature of its conductivity parameter space. The previous presented method [10], [15] is limited to one unknown conductivity: elements of the lead field matrix are approximated using polynomial interpolation based on a set of precomputed values. With this approach, the complexity of the approximation would increase fast with the number of unknown conductivities.…”

EEG Signals based Brain Source Localization Approaches

“…The BEM numerical technique calculates the surface potentials produced by current sources located in a piecewise uniform volume formed with isotropic conductivities structures [9,27]. The pieces are made in such size that they are so small for yielding isotropic conductivities [28]. There are three boundaries with the three layers in spherical model.…”