@poster{2793,
  title = {Selective Attention to Auditory Stimuli: A Brain-Computer Interface Paradigm},
  abstract = {During the last 20 years several paradigms for Brain Computer Interfaces have been proposed—
  see [1] for a recent review. They can be divided into (a) stimulus-driven paradigms, using e.g.
  event-related potentials or visual evoked potentials from an EEG signal, and (b) patient-driven
  paradigms such as those that use premotor potentials correlated with imagined action, or slow
  cortical potentials (e.g. [2]).
  Our aim is to develop a stimulus-driven paradigm that is applicable in practice to patients.
  Due to the unreliability of visual perception in “locked-in” patients in the later stages of disorders
  such as Amyotrophic Lateral Sclerosis, we concentrate on the auditory modality. Speci-
  cally, we look for the effects, in the EEG signal, of selective attention to one of two concurrent
  auditory stimulus streams, exploiting the increased activation to attended stimuli that is seen
  under some circumstances [3].
  We present the results of our preliminary experiments on normal subjects. On each of
  400 trials, two repetitive stimuli (sequences of drum-beats or other pulsed stimuli) could be
  heard simultaneously. The two stimuli were distinguishable from one another by their acoustic
  properties, by their source location (one from a speaker to the left of the subject, the other from
  the right), and by their differing periodicities. A visual cue preceded the stimulus by 500 msec,
  indicating which of the two stimuli to attend to, and the subject was instructed to count the
  beats in the attended stimulus stream. There were up to 6 beats of each stimulus: with equal
  probability on each trial, all 6 were played, or the fourth was omitted, or the fth was omitted.
  The 40-channel EEG signals were analyzed ofine to reconstruct which of the streams was
  attended on each trial. A linear Support Vector Machine [4] was trained on a random subset of
  the data and tested on the remainder. Results are compared from two types of pre-processing
  of the signal: for each stimulus stream, (a) EEG signals at the stream's beat periodicity are
  emphasized, or (b) EEG signals following beats are contrasted with those following missing
  beats. Both forms of pre-processing show promising results, i.e. that selective attention to
  one or the other auditory stream yields signals that are classiable signicantly above chance
  performance. In particular, the second pre-processing was found to be robust to reduction in
  the number of features used for classication (cf. [5]), helping us to eliminate noise.},
  volume = {7},
  pages = {102},
  editors = {B{\"u}lthoff, H.H., H.A. Mallot, R. Ulrich and F.A. Wichmann},
  organization = {Max-Planck-Gesellschaft},
  school = {Biologische Kybernetik},
  month = feb,
  year = {2004},
  slug = {2793},
  author = {Hill, NJ. and Lal, TN. and Schr{\"o}der, M. and Hinterberger, T. and Birbaumer, N. and Sch{\"o}lkopf, B.},
  month_numeric = {2}
}