Kernel Electrical Source Imaging – spatial source localization from ECoG and SEEG recordings
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1
Nencki Institute of Experimental Biology, Dept. of Neurophysiology, Poland
In epilepsy patients with pharmacologically intractable epileptic seizures surgical treatment may be the only solution. Often, noninvasive methods do not sufficiently localize epileptogenic foci and invasive methods of presurgical evaluation are necessary. These may include recordings of extracellular electric potential with depth electrodes, which is called stereoencephalography (SEEG), or with subdural electrodes placed directly over the cortex (electrocorticography, ECoG). Given these recordings one needs to estimate the spatial location of the sources in the brain that are to be lesioned. Improving the precision of localization of these sources from ECoG and SEEG recordings, which is termed electrical source imaging, is a major challenge of the field [1].
Here we propose a new method, kernel Electrical Source Imaging (kESI), which takes into account realistic brain morphology and spatial variations in brain conductivity. The method can localize multiple sources, and is flexible to arbitrary electrode positions and so it can be used effectively for a specific patient's case. The core of the method is in the construction of kernel functions requiring computation of the potentials generated in the brain by numerous basis functions covering the probed volume, which is an extension of our previous work [2].
To show the proof-of-concept we generated dipolar ground truth data inside a simplified spherical brain model with uniform conductivity. We assumed the electrodes on the surface of the sphere and inside the spherical volume emulating ECoG and SEEG style recordings respectively. The potentials generated at these electrodes were computed using Finite Element Methods (FEM) in FEniCS software, the mesh was generated in gmsh. In kESI, this FEM model was used to compute the potentials generated by the basis functions, and hence obtain the reconstructed sources. We could show how different distributions of electrodes affect the quality of reconstruction. This may lead to a procedure for prescribing optimal distributions of electrodes depending on available prior knowledge (e.g. dysfunction of specific brain structures) and clinical resources (availability of specific electrodes, etc).
Acknowledgements
Research funded from grants FP7-PEOPLE-2010-ITN 264872 NAMASEN, 2948/7.PR/2013/2.
References
1. K. Kaiboriboon, H.O. Lüders, M. Hamaneh, J. Turnbull, S.D. Lhatoo, EEG source imaging in epilepsy – practicalities and pitfalls, Nat. Rev. Neurol. 2012, 8:498-507
2. J. Potworowski, W. Jakuczun, S. Łęski, D. Wójcik, Kernel Current Source Density Method, Neural Comput. 2012, 24:541-575
Keywords:
Epilepsy,
electrocorticography,
ECoG,
Local Field Potentials,
LFP,
Current Source Density,
CSD,
kernel methods,
kernel CSD method,
kCSD,
Finite element method,
FEM
Conference:
Neuroinformatics 2015, Cairns, Australia, 20 Aug - 22 Aug, 2015.
Presentation Type:
Poster, not to be considered for oral presentation
Topic:
Electrophysiology
Citation:
Wójcik
DK and
Chintaluri
H
(2015). Kernel Electrical Source Imaging – spatial source localization from ECoG and SEEG recordings.
Front. Neurosci.
Conference Abstract:
Neuroinformatics 2015.
doi: 10.3389/conf.fnins.2015.91.00032
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Received:
07 Apr 2015;
Published Online:
05 Aug 2015.
*
Correspondence:
Prof. Daniel K Wójcik, Nencki Institute of Experimental Biology, Dept. of Neurophysiology, Warszawa, 02-093, Poland, d.wojcik@nencki.edu.pl