NeuroImage: 微创脑机接口实现思维打字

近年来发展起来的脑机接口技术可以帮助像物理学家霍金一样的神经渐冻症病人、或者是脊髓损伤导致高位截瘫的残疾人，与外界进行沟通交流。脑机接口技术借助计算机解读人脑的信号，让这类病人能够自主操纵家电或者假肢，实验室研究已经展示出可行性和应用前景，但其临床应用碰到了难题。采用无创伤的头皮脑电脑机接口技术信号质量差，无法长期稳定工作；基于植入微电极的脑机接口手术创伤大，长期植入后由于神经胶质细胞的包裹，神经信号会减弱，导致脑机交互失效。

清华大学医学院生物医学工程系洪波课题组和清华大学玉泉医院、解放军总医院神经外科合作，利用癫痫病人植入颅内电极定位病灶的手术间期，研究实现了一种基于大脑皮层表面神经信号的新型微创脑机接口。该方法与已有脑机接口技术相比，手术创伤小，神经信号长期稳定。这项工作5月1日发表于国际神经影像学期刊《神经影像》（NeuroImage）。

研究人员在病人眼前呈现一个隐藏着运动条纹的虚拟键盘，病人通过自己的视觉注意来选择想要输入的字符，被注意的字符会引起更强的神经活动。该项研究发现这种增强的神经活动主要表现为60赫兹以上的高频振荡，空间上集中于中颞叶一个很小的脑区，检测这一区域高频神经信号的能量变化就可以确定病人要输入的字符。功能磁共振扫描发现，该区域与处理视觉运动的脑区非常吻合。因为实验采用了巧妙的视觉运动设计，使得神经响应高度集中，可以通过功能磁共振精确定位。

结合功能磁共振定位信息，该项研究只获取大脑皮层表面一个电极的神经信号，实现了思维打字的功能。这项研究首次实现了通过神经影像精确定位的微创脑机接口技术，在国际上引起关注。

这项研究还展示了利用脑内大脑皮层表面的高频神经信号研究脑功能网络的独特优势：直接而精准地观测毫秒级的快速神经活动，与功能磁共振技术结合，可以为大脑皮层功能研究提供高时间分辨率和空间解析度的动态图像，是研究语言、注意、记忆等高级认知活动的有力工具。

Toward a minimally invasive brain–computer interface using a single subdural channel: A visual speller study

Electrocorticography (ECoG) has attracted increasing interest for implementing advanced brain–computer interfaces (BCIs) in the past decade. However, real-life application of ECoG BCI demands mitigation of its invasive nature by minimizing both the size of the involved brain regions and the number of implanted electrodes. In this study, we employed a recently proposed BCI paradigm that utilizes the attentional modulation of visual motion response. With ECoG data collected from five epilepsy patients, power increase of the high gamma (60–140 Hz) frequency range was found to be associated with the overtly attended moving visual stimuli in the parietal-temporal-occipital junction and the occipital cortex. Event-related potentials (ERPs) were elicited as well but with broader cortical distribution. We achieved significantly higher BCI classification accuracy by employing both high gamma and ERP responses from a single ECoG electrode than by using ERP responses only (84.22 ± 5.54% vs. 75.48 ± 4.18%, p < 0.005, paired t-test, 3-trial averaging, binary results of attended vs. unattended). More importantly, the high gamma responses were located within brain regions specialized in visual motion processing as mapped by fMRI, suggesting the spatial location for electrode implantation can be determined prior to surgery using non-invasive imaging. Our findings demonstrate the feasibility of implementing a minimally invasive ECoG BCI.