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Computational Intelligence and Neuroscience
Volume 2007, Article ID 58253, 10 pages
Research Article

Canonical Decomposition of Ictal Scalp EEG and Accurate Source Localisation: Principles and Simulation Study

1ESAT-SISTA, Katholieke Universiteit Leuven, Kasteelpark Arenberg 10, Heverlee-Leuven 3001, Belgium
2CNRS-ETIS, 6 Avenue du Ponceau BP 44, Cergy-Pontoise 95014, France
3Department of Neurology, University Hospital Gasthuisberg, Katholieke Universiteit Leuven, Herestraat 49, Leuven 3000, Belgium

Received 16 February 2007; Revised 13 June 2007; Accepted 2 October 2007

Academic Editor: Andrzej Cichocki

Copyright © 2007 Maarten De Vos et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Long-term electroencephalographic (EEG) recordings are important in the presurgical evaluation of refractory partial epilepsy for the delineation of the ictal onset zones. In this paper, we introduce a new concept for an automatic, fast, and objective localisation of the ictal onset zone in ictal EEG recordings. Canonical decomposition of ictal EEG decomposes the EEG in atoms. One or more atoms are related to the seizure activity. A single dipole was then fitted to model the potential distribution of each epileptic atom. In this study, we performed a simulation study in order to estimate the dipole localisation error. Ictal dipole localisation was very accurate, even at low signal-to-noise ratios, was not affected by seizure activity frequency or frequency changes, and was minimally affected by the waveform and depth of the ictal onset zone location. Ictal dipole localisation error using 21 electrodes was around 10.0 mm and improved more than tenfold in the range of 0.5–1.0 mm using 148 channels. In conclusion, our simulation study of canonical decomposition of ictal scalp EEG allowed a robust and accurate localisation of the ictal onset zone.