title: A real-time classification algorithm for EEG-based BCI driven by self-induced emotions.
abstract: OBJECTIVE
  The aim of this paper is to provide an efficient, parametric, general, and completely automatic real time classification method of electroencephalography (EEG) signals obtained from self-induced emotions. The particular characteristics of the considered low-amplitude signals (a self-induced emotion produces a signal whose amplitude is about 15% of a really experienced emotion) require exploring and adapting strategies like the Wavelet Transform, the Principal Component Analysis (PCA) and the Support Vector Machine (SVM) for signal processing, analysis and classification. Moreover, the method is thought to be used in a multi-emotions based Brain Computer Interface (BCI) and, for this reason, an ad hoc shrewdness is assumed.
  
  
  METHODS
  The peculiarity of the brain activation requires ad-hoc signal processing by wavelet decomposition, and the definition of a set of features for signal characterization in order to discriminate different self-induced emotions. The proposed method is a two stages algorithm, completely parameterized, aiming at a multi-class classification and may be considered in the framework of machine learning. The first stage, the calibration, is off-line and is devoted at the signal processing, the determination of the features and at the training of a classifier. The second stage, the real-time one, is the test on new data. The PCA theory is applied to avoid redundancy in the set of features whereas the classification of the selected features, and therefore of the signals, is obtained by the SVM.
  
  
  RESULTS
  Some experimental tests have been conducted on EEG signals proposing a binary BCI, based on the self-induced disgust produced by remembering an unpleasant odor. Since in literature it has been shown that this emotion mainly involves the right hemisphere and in particular the T8 channel, the classification procedure is tested by using just T8, though the average accuracy is calculated and reported also for the whole set of the measured channels.
  
  
  CONCLUSIONS
  The obtained classification results are encouraging with percentage of success that is, in the average for the whole set of the examined subjects, above 90%. An ongoing work is the application of the proposed procedure to map a large set of emotions with EEG and to establish the EEG headset with the minimal number of channels to allow the recognition of a significant range of emotions both in the field of affective computing and in the development of auxiliary communication tools for subjects affected by severe disabilities.
authors.affiliation: Department of Computer, Control and Management Engineering Antonio Ruberti, Sapienza University of Rome, Via Ariosto 25, 00185 Rome, Italy. Electronic address: iacoviello@dis.uniroma1.it.
authors.forename: Daniela
authors.initials: D
authors.lastname: Iacoviello
authors.affiliation: A(2)VI-Lab, c/o Department of Life, Health and Environmental Sciences, University of ĽAquila, Via Vetoio, 67100 ĽAquila, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Petracca
authors.affiliation: A(2)VI-Lab, c/o Department of Life, Health and Environmental Sciences, University of ĽAquila, Via Vetoio, 67100 ĽAquila, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Spezialetti
authors.affiliation: A(2)VI-Lab, c/o Department of Life, Health and Environmental Sciences, University of ĽAquila, Via Vetoio, 67100 ĽAquila, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Placidi
mesh_terms: D000328:Adult; D000465:Algorithms; D062207:Brain-Computer Interfaces / Q000706:statistics & numerical data; D003199:Computer Systems; D004569:Electroencephalography; D004644:Emotions / Q000502:physiology*; D006801:Humans; D008297:Male; D025341:Principal Component Analysis
keywords: Affective computing; BCI; Classification algorithm; EEG signals; Principal components analysis; Self-induced emotions