基于人脸范式的P300拼写系统的参数优化

Parameter Optimization in Face-Based P300 Speller System

基于P300电位的脑机接口系统,因其识别准确率高、信息传输率快,经常被用于单词拼写等信息交互系统。近年来的研究表明,人脸刺激可以诱发出非常优良的事件相关电位,从而提高P300脑机接口拼写系统的性能。然而,人脸刺激在脑机接口中的呈现方式也会直接影响人脸诱发信号的可识别性。从人脸刺激在脑机接口系统中的几种基本呈现形式展开研究,对刺激间隔(130和200 ms)、界面尺寸(15.6和24英寸)和图片像素(50×69和80×110)3个参数分别展开研究,并邀请10名健康被试参与实验。实验结果表明:离线训练阶段增大这3个参数均可显著提高单个闪烁序列的分类准确率,但在线测试阶段唯有刺激时间间隔的增加可显著提高系统的分类准确率(200 ms:90%±7%,130 ms:75%±13%)。另外,这3个参数的调整对系统诱发的N200、P300、N400等信号强度的影响也不相同。在P300拼写系统的实际应用中,应综合考虑多个物理参数的优化,以提高系统性能。

The P300 based BCI is often used in speller system,because of its high accuracy and information transfer rate. Previous studies showed that face stimulus could induce recognizable event related potentials,which improve the performance of a P300 speller system. However,the form of face stimulus presentation also directly affects the system＇s performance. The experiments we executed were under three different parameters：stimulus onset asynchrony（ SOA）（ 130 ms vs 200 ms）,the size of screen（ 15. 6 inch vs 24 inch） and image pixels（ 50 × 69 vs 80 × 110）,and 10 healthy subjects were invited to participate in this experiment. The results showed that enlarging the three parameters all improved the per-trial classification accuracy during the offline training. However,in the process of online testing,only the paradigm with 200 ms stimulus intervals achieved significantly higher online classification accuracy than that with 130 ms stimulus intervals（ 90% ± 7%vs 75% ± 13%）. Besides,the three paradigms ＇ parameter adjustments have different influences on the amplitude of ERP,such as N200,P300,N400,et al. In the practical usage of P300 speller system,parameter optimization should be taken into consideration to improve the system＇s performance.