Comparison of resting EEG coherence in patients with mild cognitive impairment and normal elderly subjects

Mild cognitive impairment (MCI) was a condition beginning before more serious deterioration, leading to Alzheimer's dementia (AD). MCI detection was needed to determine the patient's therapeutic management. Power spectral analysis of the EEG signal was commonly used to observe changes in functionality associated with MCI. Since the EEG signal contains a large amount of noise artifact, power analysis can generate bias, particularly at low frequencies. The artifacts were often mixed with a blink or eyeball movement noise. Therefore, in this study, the characterization of EEG coherence was carried out in MCI patients and normal subjects to overcome this problem. The hypothesis was that the EEG coherence might give different values to be considered as a modality in MCI detection. EEG recording from 11 MCI patients and 16 normal elderly subjects were investigated. This study investigated the inter and intra-hemispheric coherence over 16 EEG channels in the frequency range of 1-30 Hz. The simulation results showed that most of the electrode pair coherence in MCI patients have decreased compared to normal elderly subjects. In inter hemisphere coherence, significant differences (p <0.05) were found in the FP1-FP2 electrode pairs. Meanwhile, significant differences (p <0.05) were found in almost all pre-frontal area connectivity of the intra-hemisphere coherence pairs. The electrode pairs were FP2-F4, FP2-T4, FP1-F3, FP1-F7, FP1-C3, FP1-T3, FP1-P3, FP1-T5, FP1-O1, F3-O1, and T3-T5. The decreased coherence in MCI patients showed the disconnection of cortical connections as a result of the death of the neurons. Furthermore, the coherence value can be used as a multimodal feature in normal elderly subjects and MCI. It is hoped that current studies may be considered for early detection of Alzheimer's in a larger population.