Differences in quantitative electroencephalogram and voxel‐based volumetry between encoding and retrieval in amnestic mild cognitive impairment

Abstract

AbstractBackgroundAmnestic mild cognitive impairment (aMCI) has been considered as prodromal stage of Alzheimer’s disease. Memory impairment can be classified into encoding failure (EF) and retrieval failure (RF).ObjectsThe aim of this study is to classify patients with single‐dominant aMCI according to the type of memory impairment (EF and RF) and to examine the quantitative EEG and MRI brain volume with significant differences between the groups.MethodThis study used the EEG data of patients who visited Chung‐Ang University Hospital Department of Neurology from January 2012 to May 2019 and were diagnosed with single‐dominant aMCI. A total of 165 collected EEG data were classified into 87 EF (73.76 ±8.26 years) and 78 RF (73.42 ± 7.88 years) based on the results of the Seoul Verbal Learning Test. EEG was done using the standard 10–20 system (21 electrodes) using a digital electroencephalograph (Comet AS40 amplifier EEG GRASS; Telefactor, USA). The stored EEG data were subjected to quantitative EEG analysis through noise preprocessing using iSyncBrain™ (iMediSync, Inc., Korea), and group analysis was performed according to two types. Subjects were also performed 3D T1 MRI and voxel based morphometry using Computational Anatomy Toolbox for SPM 12.ResultThe beta2 band power(frequency range : 15∼20Hz) in the relative power spectrum showed statistically significant difference between the two groups in the Cz and parietal electrodes(P3, Pz, P4) (p<0.05). Also, broad area around occipito‐parietal region showed significant increase of TB2R(Theta/Beta2 power ratio) both sensor and source level analysis. Increasing pattern of TB2R was also observed in both parahippocampal area. There was no significant difference of regional brain volumes between aMCI with EF and RF.ConclusionEF and RF of aMCI showed no structural differences, but functional differences, suggesting the possibility of different stages or pathologies of cognitive impairments.