| ObjectiveTo observe the changes of EEG non-linear dynamics properties of different agesubjects under mental tasks. To investigate the changes of EEG non-lineardynamics properties of the menopause depression subjects under eyes closedstate.MethodsEEG was recorded in 15 healthy children, young, and older volunteer under fourstates: eyes closed, eyes opened, mental arithmetic with eyes closed andgraphicss reasoning, correlation dimension (D2), point-wise correlationdimension (PD2), Complexity(Cx), and Approximate Entropy (ApEn) werecalculated for all subjects. EEG was recorded and ApEn were calculated in thegroups of menopause depression subjects.Results1. There were significant differences of D2 and PD2 between original EEG data and phase randomization surrogate data.2. Under rest states, the averages of D2, PD2, Cx and ApEn at a lower level in different areas.3. The results argued for the averages of D2, PD2, Cx and ApEn increased significantly during mental tasks as compared to the rest states.4. In deferent state, D2, PD2, Cx and ApEn of children subjects are lower than the young and older subjects. There are no difference between the young and older subjects.5. D2, PD2,Cx, and ApEn are concerned by positions, cognitive tasks, subjects, and etc.6. ApEn increased significantly the group of menopause depression as compared to the group of natural comparison at eyes closed state.Conclusions1. The result of surrogate data test rejects the null hypothesis that both the original EEG data and the surrogate data can be described by a linear model, which argues for the presence of non-linearity in the EEG for all states we tested.2. The phenomenon that the values of D2, PD2, Cx and ApEn fluctuate with time indicates that the activation procedure of the regions involved in the corresponding cognitive task is intermittent.3. D2, PD2, Cx and ApEn can describe the maturation of brain.4. ApEn is appropriate for the study of mental functions changes of menopause depression.
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