title: Identifying local ultrametricity of EEG time series for feature extraction in a brain-computer interface.
abstract: The accurate discrimination of EEG times-series is a challenging problem and has become a topic of prominent research interest, given the extent of the research activity in the area of brain-computer interface (BCI) technology. Many signal processing algorithms involving preprocessing, feature extraction/selection, and classification have been deployed and yet, the most appropriate and robust solutions are still being sought. This paper presents an analysis of a new methodology for feature extraction in a BCI which is based on identifying the extent of ultrametricity from EEG time-series. This work is inspired by the idea that there are natural, not necessarily unique, tree or hierarchy structures defined by the ultrametric topology of EEG time-series. The objective is to determine if coefficients which reflect the extent of ultrametricity can be used as distinct features of different EEG time series, recorded whilst subjects imagine left/right hand movements (motor imagery(MI)). The results show that MI based EEG time-series can be separated using a local ultrametricity quantifier and a linear discriminant classifier or Bayes classifier. Also, it is shown that neural-time-series-prediction-preprocessing (NTSPP) produces a higher dimensional space in which local ultrametricity is more separable for two classes of EEG signals.
authors.affiliation: Intelligent Systems Research Center, School of Computing and Intelligent Systems, Faculty of Engineering, Magee Campus, University of Ulster, Northland Road, Derry, Northern Ireland, UK. dh.coyle@ulster.ac.uk
authors.forename: Damien
authors.initials: D
authors.lastname: Coyle
authors.forename: Thomas M
authors.initials: TM
authors.lastname: McGinnity
authors.forename: Girijesh
authors.initials: G
authors.lastname: Prasad
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D004569:Electroencephalography; D001330:Electronic Data Processing / Q000379:methods*; D005260:Female; D006225:Hand / Q000502:physiology*; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D014584:User-Computer Interface