The auditory P300-based single-switch brain-computer interface: paradigm transition from healthy subjects to minimally conscious patients.
OBJECTIVE
Within this work an auditory P300 brain-computer interface based on tone stream segregation, which allows for binary decisions, was developed and evaluated.


METHODS
Two tone streams consisting of short beep tones with infrequently appearing deviant tones at random positions were used as stimuli. This paradigm was evaluated in 10 healthy subjects and applied to 12 patients in a minimally conscious state (MCS) at clinics in Graz, Würzburg, Rome, and Liège. A stepwise linear discriminant analysis classifier with 10×10 cross-validation was used to detect the presence of any P300 and to investigate attentional modulation of the P300 amplitude.


RESULTS
The results for healthy subjects were promising and most classification results were better than random. In 8 of the 10 subjects, focused attention on at least one of the tone streams could be detected on a single-trial basis. By averaging 10 data segments, classification accuracies up to 90.6% could be reached. However, for MCS patients only a small number of classification results were above chance level and none of the results were sufficient for communication purposes. Nevertheless, signs of consciousness were detected in 9 of the 12 patients, not on a single-trial basis, but after averaging of all corresponding data segments and computing significant differences. These significant results, however, strongly varied across sessions and conditions.


CONCLUSIONS
This work shows the transition of a paradigm from healthy subjects to MCS patients. Promising results with healthy subjects are, however, no guarantee of good results with patients. Therefore, more investigations are required before any definite conclusions about the usability of this paradigm for MCS patients can be drawn. Nevertheless, this paradigm might offer an opportunity to support bedside clinical assessment of MCS patients and eventually, to provide them with a means of communication.
Institute for Knowledge Discovery, Graz University of Technology, Inffeldgasse 13, 8010 Graz, Austria.
Christoph
C
Pokorny
Daniela S
DS
Klobassa
Gerald
G
Pichler
Helena
H
Erlbeck
Ruben G L
RG
Real
Andrea
A
Kübler
Damien
D
Lesenfants
Dina
D
Habbal
Quentin
Q
Noirhomme
Monica
M
Risetti
Donatella
D
Mattia
Gernot R
GR
Müller-Putz
D000161:Acoustic Stimulation; D000328:Adult; D062207:Brain-Computer Interfaces; D004569:Electroencephalography; D018913:Event-Related Potentials, P300; D005260:Female; D006801:Humans; D008297:Male; D018458:Persistent Vegetative State / Q000503:physiopathology*
Auditory P300; Brain–computer interface; Clinical assessment; Minimally conscious state; Tone stream segregation