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Synchronized audiovisual stimulation enhances neural entrainment: convergent evidence from complementary EEG
1Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Zaragoza, Zaragoza, Spain.
Abstract:
Rhythmic sensory stimulation modulates oscillations via frequency-specific entrainment, but synchronized auditory contributions remain unclear, and periodic-aperiodic decomposition has not been applied to audiovisual entrainment. Forty adults received visual stimulation at 8, 20, and 40 Hz, alone (VF) or synchronized with binaural beats of identical frequencies (VF + BB). EEG was analyzed using power spectral density (PSD), topographical mapping, Sample Entropy (SampEn), Lempel-Ziv Complexity (LZC), Phase-Locking Regularity (PLR), and IRASA to separate periodic (SSVEP) from aperiodic (1/f) contributions. Visual flicker induced frequency-specific entrainment, and binaural beats modulated responses frequency-dependently. At 8 Hz, flicker elicited a periodic SSVEP; adding binaural beats enhanced this component and increased aperiodic activity. At 20 Hz, synchronized audiovisual stimulation enhanced both periodic and aperiodic components. At 40 Hz, IRASA showed no significant periodic modulation; VF + BB produced a widespread increase in aperiodic offset and exponent, absent under VF alone. VF + BB reduced SampEn across all frequencies and increased PLR at 8 and 20 Hz, whereas LZC decreased at 8 Hz and increased at 20 Hz. Synchronized audiovisual stimulation produced frequency-dependent changes in EEG spectral organization. At 8 and 20 Hz, adding binaural beats enhanced the periodic SSVEP component, with changes in the aperiodic background. At 40 Hz, conventional PSD showed increased gamma activity, but periodic-aperiodic decomposition did not reveal significant periodic enhancement; audiovisual stimulation primarily altered aperiodic offset and exponent. Complementary regularity and phase-based measures showed frequency-dependent temporal changes. Findings highlight combining conventional spectral analysis, periodic-aperiodic decomposition, and complementary EEG biomarkers to characterize synchronized audiovisual stimulation.