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Influence of a silastic ECoG grid on EEG/ECoG based source analysis
Benjamin Lanfer1, Christian Röer, Michael Scherg
1Institute for Biomagnetism and Biosignalanalysis, Westfälische Wilhelms-Universität Münster, Malmedyweg 15, 48149, Münster, Germany. benjamin.lanfer@uni-muenster.de
Insulating grids used for electrocorticography (ECoG) significantly impact scalp electroencephalogram (EEG) and intracranial ECoG recordings. These grids can cause errors in source reconstruction, necessitating their consideration in epilepsy surgery evaluations.
Area of Science:
- Neuroscience
- Biomedical Engineering
- Medical Physics
Background:
- Simultaneous electroencephalogram (EEG) and electrocorticogram (ECoG) recordings aid in understanding epilepsy seizure generation.
- Disruptions in brain coverings can affect the accuracy of scalp and intracranial recordings.
- ECoG electrodes are often embedded in resistive silastic sheets, potentially altering electrical conduction.
Purpose of the Study:
- To investigate the impact of insulating ECoG grids on scalp EEG and ECoG measurements.
- To assess how these grids affect source reconstruction using equivalent current dipole estimation.
- To quantify reconstruction errors in terms of source location and mislocalization.
Main Methods:
- Computer simulation study using the finite element method.
- Modeling of the volume conductor incorporating thin ECoG sheets with high-quality tetrahedral meshes.
- Constrained Delaunay tetrahedralization meshing approach for mesh generation.
Main Results:
- Insulating silastic substrates of ECoG grids significantly impact scalp potentials.
- Substantial errors in source reconstruction from scalp EEG data were observed.
- A non-negligible influence of insulating grids on ECoG-based source analysis was identified.
Conclusions:
- Thin insulating ECoG sheets have a considerable effect on scalp EEG and ECoG data.
- Source analysis of simultaneous ECoG and scalp EEG data must account for the presence of these insulating grids.
- Accurate interpretation of epilepsy evaluation data requires considering the influence of ECoG grid materials.
