Alpha power is associated with hippocampal volume in Alzheimer’s disease: A combined MEG and MRI study

Background New Therapeutics in Alzheimer’s Disease (NTAD) is a multi‐centre, longitudinal study to develop reliable and sensitive biomarkers for patients in the early stage of Mild Cognitive Impairment (MCI) and Alzheimer’s Disease (AD). The hallmark of E/MEG abnormalities in AD patients is changes to the power and frequency of the alpha rhythm. Here, we explore spontaneous alpha oscillations in the NTAD cohort and how they relate to diagnostic condition (patient vs control), resting task (eyes open vs eyes closed) and hippocampal atrophy. Method At present, there has been MRI and E/MEG data collected on neurologically healthy controls (N=15; MMSE M=29.4±0.74) and amyloid positive MCI and AD patients (N=46; MMSE M=24.8±3.37). Resting‐state E/MEG recordings were obtained for two 5‐minute sessions; eyes opened and eyes closed. Average power and peak frequency were computed for each participant. A T1‐weighted MR scan was used to calculate hippocampal volume, whilst accounting for individual brain volume. Firstly, we compared the average power and peak frequency for patients and controls in both the eyes opened and eyes closed conditions. Secondly, we explored how alpha varies across these conditions and diagnoses and how these differences relate to hippocampal volume. Result We found that patients had lower peak frequency and power compared to controls. Specifically, there was a decreased power in eyes closed, and decreased frequency in eyes opened. These differences were also present in hippocampal volume as patients had significantly smaller hippocampi than controls, and this was correlated with decreased alpha peak frequency specifically in the eyes opened session (R2 = 0.172). These individual differences were further associated with MMSE scores. Conclusion There are individual differences between alpha frequency and power between patients and controls. Alpha decreases with increasing cognitive impairment and is related to hippocampal volume. Whilst this is specific to eyes opened or eyes closed, results suggest that progressive atrophy of the hippocampus is associated with decreased alpha frequency. This confirms the clinical benefit of E/MEG measurements in dementia research and improve our understanding of the integration between structural and electrophysiological measures of synaptic dysfunction. Ongoing data analysis will be conducted to standardise these measures for future clinical trials.