Association between magnetoencephalography resting‐state brain oscillatory activity in regions with early Alzheimer’s disease neuropathology and global cortical atrophy

AbstractBackgroundPrevious magnetoencephalography (MEG) studies have shown that individuals with mild cognitive impairment and Alzheimer’s disease (AD) demonstrate increases in δ and θ, decreases in α and β, and lower ratios of relative power between high and low frequency bands compared to controls. This analysis investigates the association between global cortical atrophy, a measure of neurodegeneration, and MEG resting‐state oscillations in cortical regions that show early AD neuropathology.MethodEighteen cognitively impaired adults (mean age: 65.2 years, 56% female) and 18 age‐and‐sex‐matched controls (mean age: 65.7 years, 44% female) were included in this analysis. All completed a 6‐minute resting‐state MEG scan and a T1w structural brain MRI scan. Processed MEG data was filtered into canonical frequency bands. Mean relative power (MRP) and α/δ, β/δ, α/θ, (α+β+γ)/(δ+θ) ratios were computed for 6 AAL atlas regions: angular gyrus, anterior cingulum, hippocampus, parahippocampal gyrus, posterior cingulum, and precuneus. Global cortical volumes (GCV) normalized by intracranial volumes were computed using FreeSurfer 6.0. Linear mixed effects modeling was performed for each region, with MRP or spectral ratio as the outcome and normalized GCV as the predictor. Age and sex were covariates and cognitive status was included as a random effect.ResultNormalized GCV was negatively associated with MRP‐θ in the precuneus (β=‐0.0085, p=0.034), posterior cingulum (β=‐0.0088, p=0.032), and angular gyrus (β=‐0.0077, p=0.043); positively associated with MRP‐α in the precuneus (β=0.0161, p=0.006), posterior cingulum (β=0.0140, p=0.007), and angular gyrus (β=0.0128, p=0.027); positively associated with the α/δ ratio in the precuneus (β=0.1468, p=0.006) and posterior cingulum (β=0.1068, p=0.012); and positively associated with the α/θ ratio in the precuneus (β=0.1398, p=0.044). Higher beta coefficients were found for the cognitively impaired vs. nonimpaired for the α/δ ratio in the precuneus (β=0.1532 vs. 0.1404) and posterior cingulum (β=0.1119 vs. 0.1017) and the α/θ ratio in the precuneus (β=0.1876 vs. 0.0920).ConclusionStronger spontaneous θ activity, weaker spontaneous α activity, and lower spectral ratios are associated with global cortical atrophy, a known pathological process in AD. The precuneus α/θ ratio may be able to distinguish cognitively impaired from nonimpaired subjects and help in determining those at risk for AD.