This paper deals with a theoretical paradigm wherein the ElectroEncephaloGram (EEG) brain activity is interpreted as the macroscopic expression of a nonequilibrium oscillatory system influenced by synchronization and parametric resonance effects. In particular, within the proposed model, neural populations are regarded as interacting groups whose collective dynamics produce coherent rhythms that synchronize themselves across different time scales. On this ground, we investigate a collection of neural spectra recorded during wake-to-sleep and sleep-to-wake transitions and show that, within the theta-alpha frequency range examined here (4–12 Hz) the dominant oscillatory components exhibit approximately harmonic frequency relationship. These observations are consistent with a resonance-based interpretation. Furthermore, the EEG records acquired from an individual experiencing the wake-to-sleep and the sleep-to-wake transitions, analyzed by Fourier transform, suggest that energy transfers take place between different spectral bands, this latter showing pseudo-fine structures.



