Invariance between subjects of brain wave representations of language

In three experiments, electric brain waves of 19 subjects were recorded under several different experimental conditions for two purposes. One was to test how well we could recognize which sentence, from a set of 24 or 48 sentences, was being processed in the cortex. The other was to study the invariance of brain waves between subjects. As in our earlier work, the analysis consisted of averaging over trials to create prototypes and test samples, to both of which Fourier transforms were applied, followed by filtering and an inverse transformation to the time domain. A least-squares criterion of fit between prototypes and test samples was used for classification. In all three experiments, averaging over subjects improved the recognition rates. The most significant finding was the following. When brain waves were averaged separately for two nonoverlapping groups of subjects, one for prototypes and the other for test samples, we were able to recognize correctly 90% of the brain waves generated by 48 different sentences about European geography.

本研究开展三项实验，在多种不同实验条件下记录了19名受试者的脑电信号，实验设置包含两个核心目标：其一为验证我们能否准确识别出受试者大脑皮层正在处理的句子——该句子选自包含24或48句的句子集合；其二为探究不同受试者之间脑电信号的不变性特征。如我们此前的研究工作，本次分析流程为：对多次实验试次取平均以生成原型样本与测试样本，随后对两类样本均施加傅里叶变换，再依次经过滤波及时域逆变换处理。本研究以原型样本与测试样本间的最小二乘拟合准则作为分类依据。三项实验均证实，对受试者的脑电信号取平均可提升识别准确率。本研究最具显著性的发现如下：当将两组互不重叠的受试者的脑电信号分别取平均（一组用于生成原型样本，另一组用于生成测试样本）时，我们可正确识别出由48句关于欧洲地理的句子所诱发的90%的脑电信号。