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Multi-class Common Spatial Pattern and Information Theoretic Feature Extraction




We address two shortcomings of the common spatial patterns (CSP) algorithm for spatial filtering in the context of brain--computer interfaces (BCIs) based on electroencephalography/magnetoencephalography (EEG/MEG): First, the question of optimality of CSP in terms of the minimal achievable classification error remains unsolved. Second, CSP has been initially proposed for two-class paradigms. Extensions to multiclass paradigms have been suggested, but are based on heuristics. We address these shortcomings in the framework of information theoretic feature extraction (ITFE). We show that for two-class paradigms, CSP maximizes an approximation of mutual information of extracted EEG/MEG components and class labels. This establishes a link between CSP and the minimal classification error. For multiclass paradigms, we point out that CSP by joint approximate diagonalization (JAD) is equivalent to independent component analysis (ICA), and provide a method to choose those independent components (ICs) that approximately maximize mutual information of ICs and class labels. This eliminates the need for heuristics in multiclass CSP, and allows incorporating prior class probabilities. The proposed method is applied to the dataset IIIa of the third BCI competition, and is shown to increase the mean classification accuracy by 23.4% in comparison to multiclass CSP.

Author(s): Grosse-Wentrup, M. and Buss, M.
Journal: IEEE Transactions on Biomedical Engineering
Volume: 55
Number (issue): 8
Pages: 1991-2000
Year: 2008
Month: August
Day: 0

Department(s): Empirical Inference
Bibtex Type: Article (article)

Digital: 0
DOI: 10.1109/TBME.2008.921154
Language: en
Organization: Max-Planck-Gesellschaft
School: Biologische Kybernetik

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  title = {Multi-class Common Spatial Pattern and Information Theoretic Feature Extraction},
  author = {Grosse-Wentrup, M. and Buss, M.},
  journal = {IEEE Transactions on Biomedical Engineering},
  volume = {55},
  number = {8},
  pages = {1991-2000},
  organization = {Max-Planck-Gesellschaft},
  school = {Biologische Kybernetik},
  month = aug,
  year = {2008},
  month_numeric = {8}