title: Information transfer rate in a five-classes brain-computer interface.
abstract: The information transfer rate, given in bits per trial, is used as an evaluation measurement in a brain-computer interface (BCI). Three subjects performed four motor-imagery (left hand, right hand, foot, and tongue) and one mental-calculation task. Classification of the electroencephalogram (EEG) patterns is based on band power estimates and hidden Markov models (HMMs). We propose a method that combines the EEG patterns based on separability into subsets of two, three, four, and five mental tasks. The information transfer rates of the BCI systems comprised of these subsets are reported. The achieved information transfer rates vary from 0.42 to 0.81 bits per trial and reveal that the upper limit of different mental tasks for a BCI system is three. In each subject, different combinations of three tasks resulted in the best performance.
authors.affiliation: Ludwig Boltzmann Institute of Medical Informatics, Graz University of Technology, Austria. obermai@dpmi.tu-graz.ac.at
authors.forename: B
authors.initials: B
authors.lastname: Obermaier
authors.forename: C
authors.initials: C
authors.lastname: Neuper
authors.forename: C
authors.initials: C
authors.lastname: Guger
authors.forename: G
authors.initials: G
authors.lastname: Pfurtscheller
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D003143:Communication Devices for People with Disabilities; D004569:Electroencephalography / Q000295:instrumentation*; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007092:Imagination / Q000502:physiology; D008297:Male; D008390:Markov Chains; D008606:Mental Processes / Q000502:physiology; D016472:Motor Neuron Disease / Q000503:physiopathology / Q000534:rehabilitation*; D014584:User-Computer Interface