EEG&BCI Laboratory, Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA.
Clin Neurophysiol. 2010 Aug;121(8):1304-13. doi: 10.1016/j.clinph.2010.03.001. Epub 2010 Mar 26.
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 without the need of attention to the switch during a 'No Control' state (when not to activate the switch).
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.
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.
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.
The reliability and convenience of the developed brain-controlled switch may extend current brain-computer interface capacities in practical communication and control applications.
开发一种实用的基于运动想象的脑控开关，其功能与实际开关相当，具有可靠的低误操作率，并且方便用户在“无控制”状态（即无需激活开关时）无需关注开关。
四名健康志愿者按照外部同步信号进行预期的运动想象任务，以打开计算机屏幕上提供的虚拟开关。在“无控制”状态下，无需进行特定的心理任务。在线实时监测单个 EEG 拉普拉斯通道的β频带事件相关频率功率（事件相关去同步或 ERD）。计算机连续监测相对 ERD 功率水平，直到超过预设阈值并打开虚拟开关。
在整个“无控制”状态的五次在线研究中，受试者 1 的平均误报率最低为 0.4+/-0.9%，在此期间，受试者需要 6.8+/-0.6 秒的主动敦促时间或总共 20.5+/-1.9 秒的总响应时间才能在在线交互开关操作中反复尝试打开开关。四名受试者的平均误报率为 0.8+/-0.4%，平均主动敦促时间为 12.3+/-4.4 秒或平均响应时间为 36.9+/-13.0 秒。来自受试者 2 的离线分析表明，使用与运动想象相关的 ERD 特征的脑控开关的整体性能在 10 倍交叉验证中为 96.2%，通过计算密集型方法进一步提高到 99.0%。
使用与运动想象相关的 ERD 特征设计的新型脑控开关具有最小的误报率，并且具有合理的主动敦促时间或响应时间来激活开关。
所开发的脑控开关的可靠性和便利性可能会扩展当前脑机接口在实际通信和控制应用中的能力。
