Investigation of neurophysiological characteristics and its changes after donepezil hydrochloride treatment on mild Alzheimer's disease using EEG spatial analyses

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To clarify the neurophysiological characteristics of 17 mild Alzheimer's disease patients (ADs) (73.6±5.5 years) and 17 normal subjects (Controls) (70.3±8.9 years) using GFP, LORETA, Global components' and Microstate analyses. Stage 4 in FAST was defined as "mild" degree. We secondly investigated the brain electric changes before and 3 months after 5 mg donepezil hydrochloride administration in 3 ADs. Closed eyes resting EEG was recorded from 19 scalp sites (10/20 system).ADs showed higher GFP than Controls in delta band (1.5-6 Hz). LORETA specified that ADs showed stronger delta activity than Controls in right inferior temporal lobe including parahippocampal gyrus. Total ADAS-J cog scores decreased after the medication in 3 ADs, while beta-3 band (21.5-30 Hz) GFP increased. The GFP pattern in all of 7 frequency bands after the medication compared with before was similar to that of Controls compared with ADs. ADs showed higher Omega (global complexity) than the Controls. The Phi (generalized frequency) was correlated with the MMSE scores, the full and performance IQ scores of the Japanese WAIS-R. We obtained 4 microstate classes (A,B,C and D). There were topographic differences in class B and D between ADs and Controls. We also found increase of contribution of class A, and decrease of C in ADs compared to Controls. Duration of class C decreased in ADs.Our GFP and LORETA results suggest that ADs had brain dysfunctions, especially memory disturbances, and that donepezil gave them neural activation. Omega and Phi results indicate an increase in spatial complexity of the brain electric field in ADs, also a close relationship between slowing of the global frequency of field changes and the cognitive decline. Moreover, the differences of microstate configurations reflect cerebral organic changes in ADs, and the decrease of duration suggests a shortening of basic building block of information processing.