Lifespan Development of EEG Alpha and Aperiodic Component Sources is Shaped by the Connectome and Axonal Delays

Abstract We introduce ξ-αNET, a model of cortical activity that represents the EEG aperiodic (ξ) and α-rhythm (α) components as Hida-Matérn processes constrained by anatomical connectivity and interareal conduction delays. This approach integrates the decomposition of Spectral Granger Causality and quantifies the lifespan trajectories of spectral processes. Using Bayesian inversion on cross-spectral rsEEG data from 1,965 participants aged 5-100 years (HarMNqEEG dataset), the model estimates cortical activity showing high test-retest reliability, effective connectivity patterns, and conduction delays. Given the approximate cortical hierarchy inferred from the inverted T1w/T2w myelination map, used as a proxy for feedforward and feedback organization, the aperiodic and α components reveal opposite directional networks across the lifespan, where the aperiodic component is localized in the frontal cortex and the α component is localized in the posterior cortex, with feedforward and feedback directed connections, respectively. For both processes, we found that the spectral parameters follow a nonlinear inverted U-shape lifespan trajectory. Finally, the model uniquely estimates global conduction delays, which were negatively correlated with α frequency and with independent cortical myelination (T1w/T2w) measures, consistent with a mechanistic link between conduction delays and α-rhythm modulation.