Objective: The goal of this study was to experimentally investigate the influence of the anisotropy of white matter (WM) conductivity on EEG source localization. Methods: Visual evoked potentials (VEP) and fMRI data were recorded from three human subjects presented with identical visual stimuli. A finite element method was used to solve the EEG forward problems based on both anisotropic and isotropic head models, and single-dipole source localization was subsequently performed to localize the source underlying the N75 VEP component. Results: The averaged distances of the localized N75 dipole locations in V1 between the isotropic and anisotropic head models ranged from 0 to 6.22 ± 2.83 mm. The distances between the localized dipole positions and the centers of the fMRI V1 activations were slightly smaller when using an anisotropic model (7.49 ± 1.35-15.70 ± 8.60 mm) than when using an isotropic model (7.65 ± 1.30-15.31 ± 9.18 mm). Conclusions: Anisotropic models incorporating realistic WM anisotropic conductivity distributions do not substantially improve the accuracy of EEG dipole localization in the primary visual cortex using experimental data obtained using visual stimulation. Significance: The present study represents the first attempt using a human experimental approach to assess the effects of WM anisotropy on EEG source analysis.
Bibliographical noteFunding Information:
This work was supported in part by NIH R01EB007920 , R01EB006433 , R21EB006070 , NSF BES-0602957 , a grant from the Institute of Engineering in Medicine of the University of Minnesota, and supported in part by the Supercomputing Institute at the University of Minnesota.
- Finite element method
- Source localization
- White matter anisotropy