CHARACTERIZING APERIODIC AND PERIODIC MEG ACTIVITY IN MIXED DEMENTIA

Alterations in aperiodic and oscillatory magnetoencephalography (MEG) activity have been consistently reported in Alzheimer’s disease (AD; Martínez-Cañada et al., 2023; van Nifterick et al., 2023), but their characterization in mixed dementias remains limited. We analyzed frequency-domain markers in healthy controls (HC, n = 124), mild cognitive impairment (MCI, n = 81), dementia due to AD (n = 128), and mixed dementias combining AD with argyrophilic grain disease (AD–AGD, n = 20) or vascular dementia (AD–VD, n = 27).

Resting-state MEG power spectra (1–45 Hz) were estimated and parameterized into aperiodic (1/f) and periodic components using specparam (Donoghue et al., 2020). Three spectral features were extracted: aperiodic exponent, dominant oscillatory peak frequency, and peak power. Group differences were assessed using pairwise Cohen’s d and Welch’s t-tests (p < 0.01, uncorrected).

Group-averaged spectra showed a shift-to-the-left of the dominant peak toward lower frequencies in MCI, AD, AD–AGD, and AD–VD relative to HC, consistent with oscillatory slowing. Spectral parameterization revealed higher aperiodic exponents and lower peak frequencies in AD and both mixed-dementia groups, with MCI showing intermediate values. Peak-power differences were generally small and contrast-dependent. Effect-size maps highlighted robust HC–patient differences for the aperiodic exponent and peak frequency, whereas peak-power effects were weaker.

Overall, joint aperiodic–periodic parameterization provides sensitive and interpretable markers of neurophysiological alterations in AD and mixed dementias, consistent with excitation–inhibition imbalance and large-scale network slowing (Martínez-Cañada et al., 2023; van Nifterick et al., 2023).