【作者】 刘晶；

【导师】 明东；

【作者基本信息】 天津大学 ， 生物医学工程， 2014， 硕士

【摘要】 与传统的个体依赖型脑-机接口相比,跨个体脑-机接口的用户可以缩短或者不经历校准过程,直接对通用型系统进行使用。缩短脑-机接口校准过程意味着对肢体运动功能受损患者时间精力的节省和后续使用效果的提高,同时也更加符合面向大量健康用户的通用型脑-机接口的使用需求。然而目前已有的基于事件相关电位(ERP)的脑-机接口跨个体识别研究大多存在被试样本数少,缺少实时验证等问题,其可行性及其影响因素需要进一步的探究。针对上述问题,本文设计了两部分实验,在离线实验中利用Farwell范式视觉诱发ERP信号,采集了55名被试数据,利用相干平均算法提取ERP时域特征,并通过一种集成的线性分类器进行跨个体的字符识别,得到86.64%的平均正确率,充分显示了脑-机接口跨个体识别的可行性,其中65.45%的被试跨个体识别率达到90%,表明对大部分被试来说,系统使用前的校准过程甚至可以省略。研究中进一步对影响跨个体识别效果的因素进行了分析,其中加入被试自身信息可以明显提升跨个体模型的识别效果,相比单纯利用其自身数据建模而言,平均时间节省约93.93%,大大加快了校准进程。另外,实验结果也显示训练跨个体模型的人数以及性别等因素会对其识别效果造成影响。为了进一步验证离线分析的结论,对20名被试在相同的实验范式下进行了在线测试,利用其一周前的离线数据所建立的SD,SI,Semi SI三种模型进行字符实时预测,分别得到了97.5%,87.7%和91.1%的识别正确率,验证了同一个体不同时间的脑电信号稳定性,以及跨个体分类器在线使用的可行性。为了探索跨个体模型的可推广性,文中还在两组不同实验范式的数据集上进行了识别验证,测试了该模型的适用范围和通用性能。总之,本文研究成果从个体、时间、实验范式等多个角度,探索了跨个体通用模型的可行性,为通用型脑-机接口应用的进一步发展提供了理论与技术支持。更多还原

【Abstract】 Compared with conventional subject-depend brain-computer interface(SDBCI), a subject-independent BCI(SIBCI) can be ready-to-use for a new user with less or even no calibration procedure. The shortened calibration process means time and energy saving and improvement of subsequent use effect for patients with motor function damage. Meanwhile, it is more in line with the requirements of BCI for the large population of healthy users. However, the existing research on event-related potential(ERP) based SIBCI were only implemented in a small amount of subjects and the real time performance has not been explored yet. Therefore, the feasibility of SIBCI and its influence factors are needed to be further explored.Focusing on the above problems, this thesis designed two experiments. In offline experiment, Farwell paradigm was used to visually evoke ERP signal. 55 subjects were recruited for the experiment. Coherent average algorithm was used for extracting ERP time domain features and an ensemble of Linear Discriminant Analysis(LDA) classifiers was used for character identification. The cross-subject classification accuracy was 86.64% and it showed the feasibility of classification across individuals for BCI. 65.45% of the subjects got accuracy of above 90% which indicated that for most subjects the calibration process could be even omitted. The influence factors of the cross-subject performance were further explored. The performance could be improved by adding information from the testing subject into SI models. It fastened the calibration procedure with saving 93.93% time compared to the SD models. Besides, the results showed that the number of people for training and gender also had influence on the cross-subject performance. In order to further verify the offline analysis conclusion, an online real time experiment with the same paradigm was implemented among 20 subjects. SD, SI and Semi SI models established by data one week ago were used to test the real time data and got accuracy with 97.5%, 87.7% and 91.1% respectively. It demonstrated the individual stability of ERP signal and the feasibility of SIBCI in real time using. The generalizability of SIBCI was explored on two databases from other experiments and the scope of application and general performance of SI model was tested.In conclusion, performance of SI models were explored from various perspectives such as individual, time and experimental paradigm. It provides the theory and technology support for the further development of universal BCI application.更多还原