An iterative subspace denoising algorithm for removing electroencephalogram ocular artifacts.
BACKGROUND
Electroencephalogram (EEG) measurements are always contaminated by non-cerebral signals, which disturb EEG interpretability. Among the different artifacts, ocular artifacts are the most disturbing ones. In previous studies, limited improvement has been obtained using frequency-based methods. Spatial decomposition methods have shown to be more effective for removing ocular artifacts from EEG recordings. Nevertheless, these methods are not able to completely separate cerebral and ocular signals and commonly eliminate important features of the EEG.


METHODS
In a previous study we have shown the applicability of a deflation algorithm based on generalized eigenvalue decomposition for separating desired and undesired signal subspaces. In this work, we extend this idea for the automatic detection and removal of electrooculogram (EOG) artifacts from multichannel EEG recordings. The notion of effective number of identifiable dimensions, is also used to estimate the number of dominant dimensions of the ocular subspace, which enables the precise and fast convergence of the algorithm.


RESULTS
The method is applied on real and synthetic data. It is shown that the method enables the separation of cerebral and ocular signals with minimal interference with cerebral signals.


CONCLUSIONS
The proposed approach is compared with two widely used denoising techniques based on independent component analysis (ICA).


CONCLUSIONS
It is shown that the algorithm outperformed ICA-based approaches. Moreover, the method is computationally efficient and is implemented in real-time. Due to its semi-automatic structure and low computational cost, it has broad applications in real-time EEG monitoring systems and brain-computer interface experiments.
The School of Electrical & Computer Engineering, Shiraz University, Shiraz, Iran. Electronic address: rsameni@shirazu.ac.ir.
Reza
R
Sameni
Commissariat à l'Énergie Atomique et aux Énergies Alternatives - CEA, LIST, Laboratoire d'Analyse des Données et Intelligence des Systèmes, 91 191 Gif-sur-Yvette, CEDEX, France. Electronic address: cedric.gouy-pailler@cea.fr.
Cédric
C
Gouy-Pailler
D000465:Algorithms; D016477:Artifacts; D004569:Electroencephalography; D004585:Electrooculography; D005133:Eye Movements; D006801:Humans; D012815:Signal Processing, Computer-Assisted
Electroencephalogram denoising; Ocular artifacts; Semi-blind source separation; Subspace decomposition