Changes of EEG Spectra and Functional Connectivity during an Object-Location Memory Task in Alzheimer’s Disease

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.

Non-stationary Group-Level Connectivity Analysis for Enhanced Interpretability of Oddball Tasks

“…As observed from the target responses, the pSTh thresholding dispenses an increased connectivity between the frontal and temporal/parietal electrodes of auditory target detection. This finding is reported in Han et al (2017). Likewise, in θ and δ waves, pSTh exposes an enhanced connectivity between the medial frontal cortex and other cortical regions (including the parietal) during attention and surprise/novelty processing; this conclusion is suggested also in Gulbinaite et al (2014).…”

Frequency specific network effective connectivity: ERP analysis of recognition memory process by directed connectivity estimators

“…In [58,38] they show stronger global connectivity for successful retrieval, these results are consistent with the studies about connectivity in episodic memory as well, because We observed the almost increase in the connections of the theta and gamma frequency bands. In another study [30], they reported that in the encoding phase of patients with Alzheimer's, there are more connections in the delta, theta and alpha bands and they have strong connection in the retrieval phase in the Delta and Theta bands, but in the retrieval phase of the old words, our results show a stronger connection in the Delta and Theta bands. New words that are correctly rejected show a stronger connection in the gamma frequency bands in left parietal cortex, again like the old one.…”

“…New words that are correctly rejected show a stronger connection in the gamma frequency bands in left parietal cortex, again like the old one. maybe in that condition subjects try to use some compensation mechanism to remember the items [30].…”

A comparative clinical and encephalographic study on manifestation of the choline and dopamine deficiency syndromes in consciousness recovery after severe traumatic brain injury

“…(40 days after trauma) with akinetic mutism, from a subgroup with predominant alpha and beta activity More rarely (in 14 patients) both alpha and beta activities were presented in the EEG pattern. Others' research previously also reported the connection of a pronounced alpha activity and the state of the cholinergic system [27,28]. Dynamic studies showed that the CHD syndrome is more characteristic of the stages from mutism with speech understanding to severe cognitive decline, with 13% of all cases detected in coma.…”