title: An online three-class Transcranial Doppler ultrasound brain computer interface.
abstract: Brain computer interfaces (BCI) can provide communication opportunities for individuals with severe motor disabilities. Transcranial Doppler ultrasound (TCD) measures cerebral blood flow velocities and can be used to develop a BCI. A previously implemented TCD BCI system used verbal and spatial tasks as control signals; however, the spatial task involved a visual cue that awkwardly diverted the user's attention away from the communication interface. Therefore, vision-independent right-lateralized tasks were investigated. Using a bilateral TCD BCI, ten participants controlled online, an on-screen keyboard using a left-lateralized task (verbal fluency), a right-lateralized task (fist motor imagery or 3D-shape tracing), and unconstrained rest. 3D-shape tracing was generally more discernible from other tasks than was fist motor imagery. Verbal fluency, 3D-shape tracing and unconstrained rest were distinguished from each other using a linear discriminant classifier, achieving a mean agreement of κ=0.43±0.17. These rates are comparable to the best offline three-class TCD BCI accuracies reported thus far. The online communication system achieved a mean information transfer rate (ITR) of 1.08±0.69bits/min with values reaching up to 2.46bits/min, thereby exceeding the ITR of previous online TCD BCIs. These findings demonstrate the potential of a three-class online TCD BCI that does not require visual task cues.
authors.affiliation: Bloorview Research Institute, Holland Bloorview Kids Rehabilitation Hospital, 150 Kilgour Road, Toronto, Ontario M4G 1R8, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, Ontario M5S 3G9, Canada.
authors.forename: Anuja
authors.initials: A
authors.lastname: Goyal
authors.affiliation: Bloorview Research Institute, Holland Bloorview Kids Rehabilitation Hospital, 150 Kilgour Road, Toronto, Ontario M4G 1R8, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, Ontario M5S 3G9, Canada.
authors.forename: Ali-Akbar
authors.initials: AA
authors.lastname: Samadani
authors.affiliation: Hospital for Sick Children Research Institute, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Guerguerian
authors.affiliation: Bloorview Research Institute, Holland Bloorview Kids Rehabilitation Hospital, 150 Kilgour Road, Toronto, Ontario M4G 1R8, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, Ontario M5S 3G9, Canada. Electronic address: tom.chau@utoronto.ca.
authors.forename: Tom
authors.initials: T
authors.lastname: Chau
mesh_terms: D000328:Adult; D062207:Brain-Computer Interfaces; D003071:Cognition; D005260:Female; D006801:Humans; D007092:Imagination; D008297:Male; D020768:Middle Cerebral Artery / Q000502:physiology; D009862:Online Systems; D010775:Photic Stimulation; D017585:Ultrasonography, Doppler, Transcranial; D014705:Verbal Behavior; D055815:Young Adult
keywords: Brain computer interface; Lateralization; Motor imagery task; Online; Spatial task; Transcranial Doppler ultrasound