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Electrode and brain modelling in stereo-EEG

von Ellenrieder, Nicolas, Beltrachini, Leandro and Muravchik, Carlos 2012. Electrode and brain modelling in stereo-EEG. Clinical Neurophysiology 123 (9) , pp. 1745-1754. 10.1016/j.clinph.2012.01.019

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Objective To quantify the perturbation due to the presence of a measuring depth electrode on the intracranial electric potential distribution, and to study the effect of the heterogeneity and anisotropy of the brain tissues’ electric conductivity. Methods The governing differential equations are solved with the Boundary Elements Method to compute the perturbation on the electric potential distribution caused by the presence of the measuring electrode, and with the Finite Elements Method to simulate measurements in an heterogeneous anisotropic brain model. Results The perturbation on the measured electric potential is negligible if the source of electric activity is located more than approximately 1 mm away from the electrode. The error induced by this perturbation in the estimation of the source position is below 1 mm in all tested situations. The results hold for different sizes of the electrode’s contacts. The effect of the brain’s heterogeneity and anisotropy is more important. In a particular example simulated dipolar sources in the gray matter show localization differences of up to 5 mm between homogeneous isotropic and heterogeneous anisotropic brain models. Conclusions It is not necessary to include detailed electrode models in order to solve the stereo-EEG (sEEG) forward and inverse problems. The heterogeneity and anisotropy of the brain electric conductivity should be modeled if possible. The effect of using an homogeneous isotropic brain model approximation should be studied in a case by case basis, since it depends on the electrode positions, the subject’s electric conductivity map, and the source configuration. Significance This simulation study is helpful for interpreting the sEEG measurements, and for choosing appropriate electrode and brain models; a necessary first step in any attempt to solve the sEEG inverse problem.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Cardiff University Brain Research Imaging Centre (CUBRIC)
Subjects: Q Science > QC Physics
Uncontrolled Keywords: Stereo-EEG; Depth electrode; Forward problem; Inverse problem; Brain anisotropy
Publisher: Elsevier
ISSN: 1388-2457
Date of Acceptance: 10 January 2012
Last Modified: 08 May 2019 13:48

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