Decline in white matter volume and EEG delta oscillations in mild cognitive impairment

Abstract

AbstractBackgroundChanges in white matter (WM) may be associated with progression and risk of Alzheimer’s disease (AD) (Nasrabady et. al, 2018) along with conversion to Mild Cognitive Impairment (MCI) (Smith et. al, 2008). Total WM volume and its relation with EROs in MCI remain unclear. As a general notion, greater delta EROs occurring in the post‐stimulus time‐period indicate better cognitive responses in contrary to dynamics of resting state EEG. Surgical WM disruptions are associated with alterations more prominently in low frequency brain oscillations (EROs) (Hawasli et al, 2016). The current study aims to investigate WM volumes and EROs in cognitively unimpaired individuals (CU) and MCI.MethodSixteen individuals with MCI were compared with demographically matched 16 CU using EROs elicited by a visual classical‐oddball paradigm along with WM volumes obtained 3D T1‐weighted TFE‐sequence. WM volumes analyzed with univariate ANOVA. Repeated measures ANOVAs conducted for delta(0.5‐3.5Hz), theta(4‐7Hz), alpha(8‐13Hz), beta(15‐30Hz), and gamma(30‐48Hz) amplitudes. Binary logistic regression analyses conducted for significant WM volume variables and EROs. Correlations between WM and EROs were analyzed with Person correlation coefficient.ResultDelta ERO amplitudes were diminished [F(5,145) = 3.373,p = .035] in MCI at frontal (p = .011), central (p = .014) and parietal (p = .006) electrode locations. Furthermore, WM in right middle orbitofrontal [F(1,29) = 4.599,p = .041], left inferior temporal [F(1,29) = 4.198,p = .049] and left parahippocampal gyrus [F(51,29) = 5.182,p = .030] demonstrated less volume in MCI compared to CU. Binary logistic regression indicated that [X2(9) = 26.615,p = .002] combined WM volumes and delta EROs can classify MCI and CU with 87.1% accuracy. There were positive correlations between occipital delta and left (r = .501, p = .003) and right gyrus rectus (r = .374, p = .003) WM volumes.ConclusionThis study showed WM volumes and delta EROs were reduced in MCI. Decreased amplitudes of delta EROs seem to reflect volume loss of WM in MCI, possibly indicating an underlying demyelination or axonal loss. Delta EROs and WM changes may be helpful tools to monitor MCI focusing on axons and myelination/oligodendrocytes. Furthermore, their combined measurements can classify MCI from healthy individuals sufficiently.