Correlation of Neural Oscillations during Stroop Testing with Hippocampal and Amygdala Volume differ between Cognitively Healthy Normal Aging and Pre‐symptomatic Alzheimer’s Disease
Authors: Arakaki Xianghong , Wei Ke , Tran Thao , Liu Quanying , Fonteh Alfred N. , Harrington Michael G. , King Kevin S. 
Published: April 2020

Background and Objectives

Stroop interference differences have been reported in the early stage of pre‐symptomatic Alzheimer’s disease (AD). The two most reported brain regions in AD (hippocampus and amygdala) haven’t been studied for interference processsing in the early AD stage. We aim to explore the relationship between brain interference processing and volumetric analysis on hippocampus and amygdala to understand the underlying neural events in pre‐symptomatic AD.

Methods

We employed a quantitative electroencephalography (qEEG) test to investigate brain activity during the Stroop interference test in a pre‐symptomatic AD study. Participants were instructed to name the color of the ink when the word and color match (congruent trials (CT)) or do not match (incongruent trials (IT)). Elderly study participants with normal cognition were recruited from the local community, consisting of two subgroups according to their cerebrospinal fluid proteins: cognitively healthy with normal amyloid/tau ratio (CH‐NAT, n=20) or pathological amyloid/tau ratio (CH‐PAT, n=21) between 60–95 years of age. A subgroup of the participants went through MRI scanning (9 CH‐NATs and 9 CH‐PATs) to obtain anatomical structures. They are age, gender, BMI, education balanced. We explored correlations between qEEG spectral power (2–30Hz) at six brain regions (frontal (F), central (C), parietal (P), left temporal (LT), right temporal (RT), and occipital (O)), and the magnetic resonance imaging (MRI) volumetric measures of two brain regions that most relate to Alzheimer’s disease: hippocampus and amygdala.

Results & Discussion

In CH‐NATs but not CH‐PATs, hippocampal volume is negatively correlated with early beta power during incongruent trials (IT) (p=0.002~0.021, r=−0.87~ −0.75), and early alpha power (p=0.0004~0.020, r=−0.92~ −0.75) over F,C,P,LT,RT regions. However, in CH‐PATs but not CH‐NATs, hippocampal volume is positively correlated with both early and late delta power during incongruent trials (IT) (p=0.001~0.042, r=0.68~0.90) over C,LT,RT,O regions.

In CH‐NATs but not CH‐PATs, amygdala volume is negatively correlated with early alpha power (p=0.0003~0.0496, r=−0.93~ −0.67) on both CT (over F,C,LT,RT,O) and IT (over F,C,P,LT). However, CH‐PATs but not CH‐NATs, amygdala volume is positively correlated with late delta power during incongruent trials (IT) (p=0.007~0.023, r=0.74~0.82) over C,P,RT,O regions.

The different correlations of qEEG with MRI between CH subgroups indicate maladaptive neuroplasticity already occurs in pre‐symptomatic AD stage. Previous studies have shown that amygdala atrophy is a prominent indicator of AD severity in patients including a potential relationship with aberrant motor behavior, anxiety, and irritability. We propose that early intervention strategies for pre‐symptomatic AD individuals that correct maladaptive neuroplasticity may attenuate neurodegeneration.

Support or Funding Information

Acknowledgment

Financial support provided by the L.K. Whittier Foundation, NIH R56 Funding 1R56AG063857‐01. Betty Chung and David Buennagel assisted with patient recruitment. Roger Rochart assisted with final draft.