脑电非线性分析在认知功能研究中的应用

目的　探讨在不同认知作业状态下脑电非线性动力学特性的变化规律、脑电非线性动态分析在认知过程研究中的作用。方法　我们用关联维数 (D2 )、点关联维数 (PD2 )对 30名健康成年人四种状态下的脑电数据进行了分析 :安静闭眼、安静睁眼、闭眼心算作业和睁眼图形推理作业。结果　认知作业过程相对于安静状态 ,D2 和PD2 有明显的升高。闭眼和心算 ,睁眼和图形推理状态之间差异有显著意义 (D2 分别为 3 93和 4 33,P <0 0 1;4 4 7和 4 98,P <0 0 1)。D2 和PD2 随时间存在时高时低的现象。结论　动态的、短时程的非线性动力学分析方法 ,更适合研究认知过程中大脑功能活动的变化规律。以D2 和PD2 地形图为基础的动态分析 ,可以清晰地展示认知过程中D2 和PD2的分布情况及与认知作业相关的大脑部位活跃顺序和活跃程度的变化 ,有助于我们了解认知过程中大脑的工作机制。

Application of EEG non-linear analysis in cognitive function research

Objective To investigate the changes of non-linear dynamics properties of EEG under different mental tasks,and the application of non-linear dynamic analysis for cognitive function research. Methods EEG was recorded in 30 healthy university students under four states: eyes closed,eyes open,mental arithmetic with eyes closed and graphic reasoning test with eyes open.Correlation dimension (D 2) and point-wise correlation dimension (PD 2) were calculated for all subjects.We also performed a surrogate data test in 5 randomized selected subjects. Results In all states tested,the results argued for the presence of non-linearity and fractal D 2 and PD 2.D 2 and PD 2 increased significantly during mental tasks as compared to the rest states (D 2 of above four states was 3.93,4.47,4.33 and 4.98 respectively).The results showed that values of D 2 and PD 2 fluctuated with time,which suggests an intermittent activation of the brain areas participated in the task.With non-linear dynamic analysis,there might be a working circuit from bilateral temporal lobes to the left frontal lobe and parental lobe under mental arithmetic task.Conclusions Through dynamic analysis based on D 2 and PD 2 topographic maps,we can see clearly the distribution of D 2 and PD 2 in the brain,the sequence and the degree of activation of the regions involved in the cognitive task under mental tasks.Dynamic and short-time non-linear analysis methods are more appropriate for the study of mental functions.Non-linear dynamic analysis might help us understand the working mechanism of brain during mental activities.