Study On EEG Complexity Of Patients With Mild Cognitive Impairment At The States Of Resting And Cognitive Performance

Objective To evaluate the features of electroencephalography(EEG) Lemple-Zie Complexity(LZC) in MCI and healthy control subjects at the states of resting and cognitive performance( including the mental arithmetic tasks and associative learning tasks)Method This study enrolled 24 MCI patients(MCI group) with memory complaint from the neurological clinic in Tianjin Medical University General Hospital during March, 2014 to March, 2015. Twenty normal volunteers matched in gender, age, and educational levels were recruited as healthy control group. All subjects underwent Mini-Mental State Examination(MMSE), Montreal Cognitive Assessment Scale(Mo CA), and Clinical Memory Scale(CMS). EEG signals of two groups at resting and cognitive performance states were recorded respectively. Then the values of EEG were calculated on Matlab 7.10.Results 1 Compared with the normal controls, the MCIs showed the significant lower scores in MQ and the 5 subtests including directional memory, associative learning, free graphic memory, meaningless graphic recognition and portrait characteristics memory(P<0.001). 2 There was no significant difference in EEG LZC between two groups at rest state(P>0.05), however, the MCIs had higher LZC values than healthy controls in FP2, F4, P4, O2, and T4(P<0.05). The same results could be found in regions of right frontal, right occipital, and right hemisphere(P<0.05) when mental arithmetic tasks were performed. 3 The LZC values of healthy controls in FP1, FP2, F3*, C3, F7, and in the regions of left frontal*, right frontal, left central, and left brain hemisphere in mental arithmetic tasks state were lower than those in resting state, while the same results were found only in FP1, FP2*, F3, F8, left frontal*, and right frontal regions in MCI(P<0.05,P*<0.01). 4 During the associative learning tasks performing,the LZC in healthy controls decreased significantly compared to the resting state in FP1(P<0.01),while in MCI the same tendency existed only in F8(P<0.05)Conclusions 1 The MCIs suffered from extensive memory declining according to the scores in CMS and each its subtest. 2 The LZC values of EEG failed to distinguish the MCIs from healthy control at resting state, however, LZC values in the mental arithmetic tasks state could reveal the variation of non-linear dynamics of EEG and the notable difference between the two groups. 3 The MCIs showed a declining function in cognitive tasks related brain areas without hemispherical preponderance unlike that in the controls. Meanwhile, the compensatory in other area, especially in the other hemisphere could emerge, which offset the functional declining and make the MCIs maintain their cognitions in some degree.