The Change Of EEG, Memory In Mild Cognitive Impairment And Normal Aged:a Three-year Follow-up

ObjectiveTo explore the characteristic variation of EEG, memory in mild cognitive impairment (MCI) and the normal control (NC) during three years’follow-up.MethodThirty-seven right-handed subjects (11patients as MCI group and14normal aged mathched as control group) participated in this study. The MCI group was selected from patients who had consulted a memory clinic for memory complaints at Tianjin Medical University General Hospital. The normal aged controls were recruited from the local community. Data from the two groups were excluded due to the difference of age, sex, and education. EEG of the all subjects were recorded before and after three years for5-10minute with rest and eye-closed status (16-channel,0.3-45Hz band pass,200Hz for sampling frequency), as well as Clinic Memory Scale, and Standard scalp electrodes were placed in accordance with International10-20System. The EEG signals were recorded with a time constant0.3s and0.3-45Hz band pass filter. More than10.24s’data (2048points) were chosen for Lemple-Ziv Complexity (LZC) and the alpha relative power percentage (ARPP) were calculated on MATLAB7.0software platform.Results1. The scores of directional memory, meaningless graphic recognition in MCI group exhibited less than those in the controls at the baseline of our observation (P<0.05), and the score of mentioned above in both two groups had a continuing decrease during the three-year follow-up (P<0.05). Furthermore, the associative learning in MCI also showed a significant decline in this period (P<0.05).2. At the beginning of the observation, compared with MCI ARPP of NC revealed that left hemisphere, FP1, F3, C3, F7, F8, T3, T5was higher than that of MCI (P<0.05). In MCI group ARPP in left hemisphere, frontal and frontal lobe was lower that in the right side (P<0.05, P<0.01). Three years later, MCI group had a lower ARPP in left hemisphere, left temporal lobe, F3, P3,01,02, T3, T5than NC (P<0.05, P<0.01). During the whole three years’observation, ARPP of MCI and NC both decreased in all the electrodes (P<0.05, P<0.01), especially FP2, F4, C4, F7, F8, T6in MCI and FP2, F3, F4, C4, P4,01,02, F7, F8, T3, T4, T5in normal controls. MCI group performed positive correlation between the decrease amplitude of meaningless graph recognition and ARPP in right hemisphere, frontal and temporal lobe (P<0.05, P<0.01), and the same for directional memory in all the electrodes except FP1, F3, C3(P<0.05, P<0.01).3. The value of LZC kept higher in the left cerebral hemisphere than the offside in NC group (P<0.05) during the observation. In MCI, the value of LZC in FP1, C3,02, F7, T3, T5showed lower than those in normal controls (P<0.05, P<0.01) at the beginning of observation. Compared with the observation baseline, the EEG LZC values in MCI group decreased in F8, T5(P<0.05), while the controls had no obvious change (P>0.05). At the end of observation, the NC group had higher LZC value than MCI in left frontal, temporal lobe, FP1,C3,F7,T3,T5(P<0.05).Conclusions1. The directional memory and meaningless graphic recognition exhibit decrease in the early stage of cognitive impairment appearance, and these items will keep falling as time passed, with associative learning in MCI group additionally.2. The relative power percentage of alpha shows that the brain function could decrease with age in frontal and temporal lobe.3. The complexity value of EEG in the normal aged distributes unevenly, the left cerebral hemisphere achieves more predominantly, but in MCI on the contrary.4. The normal aged controls exhibit hypomnesis with aged, while EEG non-liner complexity higher in the superiority hemisphere. Meantime, for MCI EEG complexity value in superiority hemisphere existed such a continuous decrease that the non-dominant hemisphere become to predominate.