Abstract
Object-location memory is particularly fragile and specifically impaired in Alzheimer’s disease (AD) patients. Electroencephalogram (EEG) was utilized to objectively measure memory impairment for memory formation correlates of EEG oscillatory activities. We aimed to construct an object-location memory paradigm and explore EEG signs of it. Two groups of 20 probable mild AD patients and 19 healthy older adults were included in a cross-sectional analysis. All subjects took an object-location memory task. EEG recordings performed during object-location memory tasks were compared between the two groups in the two EEG parameters (spectral parameters and phase synchronization). The memory performance of AD patients was worse than that of healthy elderly adults The power of object-location memory of the AD group was significantly higher than the NC group (healthy elderly adults) in the alpha band in the encoding session, and alpha and theta bands in the retrieval session. The channels-pairs the phase lag index value of object-location memory in the AD group was clearly higher than the NC group in the delta, theta, and alpha bands in encoding sessions and delta and theta bands in retrieval sessions. The results provide support for the hypothesis that the AD patients may use compensation mechanisms to remember the items and episode.
Highlights
Alzheimer’s disease (AD) is a degenerative brain disease, and episodic memory impairment is an early sign of it
Mini-Mental State Examination (MMSE) correlated significantly with the number of later remembered the location (LR-L) items (r = 0.575, p < 0.01) and the number of correctly recalled total (CR-T) items (r = 0.748, p < 0.01) in two groups. These results indicate that the function of object-location memory in AD patients is obviously impaired compared to healthy elders
Higher spectral power was found in alpha band frequencies in the AD group than in the healthy control group during object-location memory encoding
Summary
Alzheimer’s disease (AD) is a degenerative brain disease, and episodic memory impairment is an early sign of it. Numerous studies have focused on the early detection of episodic memory impairment to resolve the differential diagnosis, estimate the disease progression, and determine eligible treatment. A few studies have demonstrated that spatial memory of AD patients is impaired, such as route learning tasks and scene memory assessment (Cherrier et al, 2001; deIpolyi et al, 2007; Iaria et al, 2007; Bird et al, 2010; Moodley et al, 2015). It was reported that impairments of spatial memory are typical and early symptoms of AD (Parra et al, 2010; Pertzov et al, 2012, 2013)
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