Complexity analysis of electroencephalogram in patients with Alzheimer’s disease and mild cognitive mpairment

Abstract

Objective To investigate the Lemple-Zie complexity (LZC) characteristics in patients with Alzheimer’s disease (AD)，mild cognitive impairment (MCI) and normal elderly，and the possibility of differentiating AD，MCI and normal elderly by LZC. Methods Electroencephalogram (EEG) of 30 AD patients，30 MCI patients and 20 normal elderly with eyes closed in rest state were recorded.In acquired EEG data，2048 points (10.14 s) of each channel were selected for LZC calculation by Matlab 7.0 software. Results (1) The average LZC values in AD，MCI and control groups were 0.396±0.036，0.470±0.051，0.523±0.055 respectively.As compared with control group，the values in AD and MCI groups were decreased (F=43.092，P=0.000). (2) LZC values of AD in all channels (from 0.373±0.042 to 0.430±0.083)，whole brain，bilateral hemispheres，frontal and temporal areas were significantly lower than those in the normal group (from 0.498±0.067 to 0.566±0.059;t=3.602-8.747，P=0.000-0.010)，and showed the significant decline (>23%) in bilateral anterior middle temporal，frontal areas，the left parietal area. (3) Except the T6 channel，LZC values of AD groups in the remaining channels (from 0.373±0.042 to 0.418±0.063)，the whole brain，bilateral hemispheres，frontal and temporal areas were significantly lower than those in the MCI group (from 0.455±0.072 to 0.489±0.063; in T5 channel，t=2.038，P=0.041，the others t=4.178-7.424，all P=0.000). (4) LZC values of MCI groups in the whole brain，bilateral hemispheres，temporal areas，parietal areas，the left frontal area were notably lower than those in the control group. Conclusions With the decline of the cognitive function，the EEG complexity value shows the parallel change.It suggests that the EEG complexity value can reflect the change of brain function in the duration from normal age to dementia in some degree; The MCI patients with abnormal LZC values in temporal and frontal lobes have a certain degree relation with the occurrence of AD. Key words: Alzheimer disease; Cognition disorders; Electroencephalography