A motor imagery-based online interactive brain-controlled switch: Paradigm development and preliminary test Kai Qian a , Plamen Nikolov a , Dandan Huang a , Ding-Yu Fei a , Xuedong Chen b , Ou Bai a, * a EEG&BCI Laboratory, Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA b School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China article info Article history: Accepted 2 March 2010 Available online 26 March 2010 Keywords: Brain-controlled switch Brain–computer interface (BCI) Event-related desynchronization (ERD) Electroencephalography (EEG) Motor imagery abstract Objective: To develop a practical motor imagery-based brain-controlled switch as functional as a real- world switch that is reliable with a minimal false positive operation rate and convenient for users with- out the need of attention to the switch during a ‘No Control’ state (when not to activate the switch). Methods: Four healthy volunteers were instructed to perform an intended motor imagery task following an external sync signal in order to turn on a virtual switch provided on a computer screen. No specific mental task was required during the ‘No Control’ state. The beta band event-related frequency power (event-related desynchronization or ERD) from a single EEG Laplacian channel was monitored online in real-time. The computer continuously monitored the relative ERD power level until it exceeded a pre-set threshold and turned on the virtual switch. Results: Subject 1 achieved lowest average false positive rate of 0.4 ± 0.9% in a five-session online study during the entire ‘No Control’ state, whereby the subject required 6.8 ± 0.6 s of active urging time or total response time of 20.5 ± 1.9 s to perform repeated attempts in order to turn on the switch in the online interactive switch operation. The average false positive rate among four subjects was 0.8 ± 0.4% with average active urging time of 12.3 ± 4.4 s or average response time of 36.9 ± 13.0 s. Offline analysis from subject 2 shows that the overall performance from 10-fold cross-validation was 96.2% with 3 consecutive epoch averaging, which was further improved to 99.0% by computationally intensive methods. Conclusions: The novel design of the brain-controlled switch using the ERD feature associated with motor imagery achieved minimal false positive rate with a reasonable active urging time or response time to activate the switch. Significance: The reliability and convenience of the developed brain-controlled switch may extend cur- rent brain–computer interface capacities in practical communication and control applications. Ó 2010 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved. 1. Introduction Noninvasive EEG-based brain–computer interfaces (BCIs) pro- vide an augmented communication channel for individuals who do not have the motor function capabilities necessary to interact with the external world by controlling a device, such as robotic arm, wheel chair, or computer (Wolpaw et al., 2002), and also for able bodied individuals to interact with media applications such as Google earth (Scherer et al., 2007), virtual environment (Scherer et al., 2008) as a new human–machine interface, or even prove suitable as a biometric measure for person identification (Pfurtsch- eller and Neuper, 2006; Pfurtscheller and Solis-Escalante, 2009). The majority of the past BCI investigations have been performed on a trial-based continuous control. An example of the aforemen- tioned control includes the cursor control introduced by Wolpaw’s group, wherein a cursor at left side of monitor starts moving at the beginning of each trial while requiring the users to keep sustained attention and continuously regulate their brain activities to control cursor vertical position until the cursor reaches the right side of the monitor (Wolpaw et al., 1991; McFarland et al., 2003). In contrast to the trial-based BCI designs, a couple of research groups explored self-paced or asynchronous designs for continuous BCI operation to differential ‘Intentional Control’ state from ‘No Control’ state; Birch’s group employed a slow cortical potentials (SCP)-like low frequency EEG signals, formally known as low frequency asynchro- nous switch design (LF-ASD) (Mason and Birch, 2000; Birch et al., 2002) as well as the improved versions (Bashashati et al., 2006), Pfurtscheller’s group employed Mu rhythm-based event-related desynchronization (ERD) design (Pfurtscheller et al., 2005; 1388-2457/$36.00 Ó 2010 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.clinph.2010.03.001 * Corresponding author. Address: Department of Biomedical Engineering, Vir- ginia Commonwealth University, 401 West Main Street, Room 1252, Richmond, P.O. Box 843067, VA 23284-3067, USA. Tel.: +1 804 827 3607; fax: +1 804 828 4454. E-mail address: obai@vcu.edu (O. Bai). Clinical Neurophysiology 121 (2010) 1304–1313 Contents lists available at ScienceDirect Clinical Neurophysiology journal homepage: www.elsevier.com/locate/clinph