Application Of EEG Nonlinear Analysis In Cognitive Function Research And Monitoring Of Depth Of Anesthesia

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 (D2) and point-wise correlation dimension (PD₂) 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 D₂ and PD₂. D₂ and PD₂ increased significantly during mental tasks as compared to the rest states (D₂ of above four states was 3.93, 4.47, 4.33 and 4.98 respectively). The results showed that values of D₂ and PD₂ 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 D₂ and PD₂ topographic maps, we can see clearly the distribution of D₂ and PD₂ 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.