Classification of multi-class motor imagery with a novel hierarchical SVM algorithm for brain–computer interfaces

Enzeng Dong, Changhai Li, Liting Li, Shengzhi Du, Abdelkader Nasreddine Belkacem, Chao Chen

Research output: Contribution to journalArticlepeer-review

89 Citations (Scopus)


Pattern classification algorithm is the crucial step in developing brain–computer interface (BCI) applications. In this paper, a hierarchical support vector machine (HSVM) algorithm is proposed to address an EEG-based four-class motor imagery classification task. Wavelet packet transform is employed to decompose raw EEG signals. Thereafter, EEG signals with effective frequency sub-bands are grouped and reconstructed. EEG feature vectors are extracted from the reconstructed EEG signals with one versus the rest common spatial patterns (OVR-CSP) and one versus one common spatial patterns (OVO-CSP). Then, a two-layer HSVM algorithm is designed for the classification of these EEG feature vectors, where “OVO” classifiers are used in the first layer and “OVR” in the second layer. A public dataset (BCI Competition IV-II-a)is employed to validate the proposed method. Fivefold cross-validation results demonstrate that the average accuracy of classification in the first layer and the second layer is 67.5 ± 17.7% and 60.3 ± 14.7%, respectively. The average accuracy of the classification is 64.4 ± 16.7% overall. These results show that the proposed method is effective for four-class motor imagery classification.

Original languageEnglish
Pages (from-to)1809-1818
Number of pages10
JournalMedical and Biological Engineering and Computing
Issue number10
Publication statusPublished - Oct 1 2017
Externally publishedYes


  • Common spatial pattern
  • Electroencephalography (EEG)
  • Hierarchical support vector machine (HSVM)
  • Motor imagery

ASJC Scopus subject areas

  • Biomedical Engineering
  • Computer Science Applications


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