Resting State Alpha Electroencephalographic Rhythms Are Differently Related to Aging in Cognitively Unimpaired Seniors and Patients with Alzheimer’s Disease and Amnesic Mild Cognitive Impairment

Abstract

Background: In relaxed adults, staying in quiet wakefulness at eyes closed is related to the so-called resting state electroencephalographic (rsEEG) rhythms, showing the highest amplitude in posterior areas at alpha frequencies (8–13 Hz). Objective: Here we tested the hypothesis that age may affect rsEEG alpha (8–12 Hz) rhythms recorded in normal elderly (Nold) seniors and patients with mild cognitive impairment due to Alzheimer’s disease (ADMCI). Methods: Clinical and rsEEG datasets in 63 ADMCI and 60 Nold individuals (matched for demography, education, and gender) were taken from an international archive. The rsEEG rhythms were investigated at individual delta, theta, and alpha frequency bands, as well as fixed beta (14–30 Hz) and gamma (30–40 Hz) bands. Each group was stratified into three subgroups based on age ranges (i.e., tertiles). Results: As compared to the younger Nold subgroups, the older one showed greater reductions in the rsEEG alpha rhythms with major topographical effects in posterior regions. On the contrary, in relation to the younger ADMCI subgroups, the older one displayed a lesser reduction in those rhythms. Notably, the ADMCI subgroups pointed to similar cerebrospinal fluid AD diagnostic biomarkers, gray and white matter brain lesions revealed by neuroimaging, and clinical and neuropsychological scores. Conclusion: The present results suggest that age may represent a deranging factor for dominant rsEEG alpha rhythms in Nold seniors, while rsEEG alpha rhythms in ADMCI patients may be more affected by the disease variants related to earlier versus later onset of the AD.

What a Single Electroencephalographic (EEG) Channel Can Tell us About Alzheimer's Disease Patients With Mild Cognitive Impairment

“…Specifically, groups of ADD and ADMCI patients were characterized over the Nold control seniors by the decrease in alpha power density or estimated cortical source activities and decreased theta-delta power density or estimated cortical source activities. [6][7][8][9][10][11][12] At the individual level, previous rsEEG studies reported that the ratio of rsEEG power density at delta, theta, and alpha frequency bands was able to classify ADMCI patients at the individual level with an accuracy of around 80% (AUROC). Other research consortia obtained similar results with rsEEG recordings in standard hospital settings.…”

“…Specifically, the individual alpha 1 and alpha 2 bands were computed as follows: alpha 1 from TF to the frequency midpoint of the TF-IAF range and alpha 2 from that midpoint to IAF. The other bands were defined based on the standard fixed frequency ranges used in the reference study 11 : beta 1 from 14 to 20 Hz, beta 2 from 20 to 30 Hz, and gamma from 30 to 40 Hz.…”

“…As compared to cognitively unimpaired old (Nold) seniors, patients with AD dementia (ADD) showed the following abnormalities: (1) widespread decrease in the magnitude of alpha rhythms; (2) decreased dominant alpha frequency to 8–7 Hz 6 ; (3) widespread increase in the magnitude of theta and delta rhythms; and 4) more negligible magnitude reactivity of alpha rhythms during the eye-opening. 6 Those abnormalities were also reported in ADMCI patients 7, 8,9 about the so-called “cognitive reserve” related to years of education, 10 aging, 11 and sex. 12…”

Sharpening Working Memory With Real-Time Electrophysiological Brain Signals: Which Neurofeedback Paradigms Work?

“…This EEG wave is the most common wave seen during awake states ( Adrian and Matthews, 1934 ). Global alpha power is more abnormal in younger MCI and AD patients ( Babiloni et al, 2021b ). Posterior alpha sources are more abnormal in male MCI/AD patients ( Babiloni et al, 2021c ).…”