Alpha desynchronization during simple working memory unmasks pathological aging in cognitively healthy individuals

Abstract

Our aim is to explore if cognitive challenge combined with objective physiology can reveal abnormal frontal alpha event-related desynchronization (ERD), in early Alzheimer’s disease (AD). We used quantitative electroencephalography (qEEG) to investigate brain activities during N-back working memory (WM) processing at two different load conditions (N = 0 or 2) in an aging cohort. We studied 60–100 year old participants, with normal cognition, and who fits one of two subgroups from cerebrospinal fluid (CSF) proteins: cognitively healthy (CH) with normal amyloid/tau ratio (CH-NAT, n = 10) or pathological amyloid/tau ratio (CH-PAT, n = 14). We recorded behavioral performances, and analyzed alpha power and alpha spectral entropy (SE) at three occasions: during the resting state, and at event-related desynchronization (ERD) [250 ~ 750 ms] during 0-back and 2-back. During 0-back WM testing, the behavioral performance was similar between the two groups, however, qEEG notably differentiated CH-PATs from CH-NATs on the simple, 0-back testing: Alpha ERD decreased from baseline only in the parietal region in CH-NATs, while it decreased in all brain regions in CH-PATs. Alpha SE did not change in CH-NATs, but was increased from baseline in the CH-PATs in frontal and left lateral regions (p<0.01), and was higher in the frontal region (p<0.01) of CH-PATs compared to CH-NATs. The alpha ERD and SE analyses suggest there is frontal lobe dysfunction during WM processing in the CH-PAT stage. Additional power and correlations with behavioral performance were also explored. This study provide pilot information to further evaluate whether this biomarker has clinical significance.

<p>The Joint Influence of Online Rating and Product Price on Purchase Decision: An EEG Study</p>

“…Previous studies have found that the alpha rhythms were broadly associated with attention and memory processing, and the magnitude of alpha-ERD was positively correlated with cognitive processing. 21,22,24,[36][37][38] Online purchase decision involved a complex cognitive process where working memory system and long-term memory system jointly interacted with each other. Our findings suggested that positive rating would trigger more mental activity during the process of online shopping decision, based on the cognitive implication of alpha-ERD.…”

Compromised Behavior and Gamma Power During Working Memory in Cognitively Healthy Individuals With Abnormal CSF Amyloid/Tau

“…Our longitudinal study showed that CH-PATs had a significantly higher risk of cognitive decline to mild cognitive impairment (MCI) or AD compared to CH-NATs over four years (Wilder et al, 2018;Harrington et al, 2019). We also found CH-PATs present hyper-excitability during low load WM challenge shown by alpha event-related desynchronization (ERD) during quantitative EEG (qEEG) recordings (Arakaki et al, 2019).…”

“…Studies have shown that alpha and gamma are associated during WM processing (Harrington et al, 2013;Arakaki et al, 2019). However, we do not know the role gamma power plays in WM processing in CH-PATs.…”

“…We explored gamma power in our published dataset of 24 cognitively healthy participants whose ages ranged from 60 to 100 years for the pilot study (Arakaki et al, 2019). Briefly, an equal number of participants from each socioeconomic class was coded for the investigator to remain unbiased.…”

“…Studies have demonstrated that AD patients have working memory (WM) dysfunction (Salthouse and Ferrer-Caja, 2003;Salthouse, 2003;Sperling et al, 2011). In addition, previous studies have shown that working memory begins to decline by 18 years of age, and EEG alpha power during WM processing is dysfunctional beginning in early AD (Rabinowitz et al, 1982;Craik et al, 1987;Craik and Dirkx, 1992;Salthouse, 2003;Arakaki et al, 2019).…”