INTRODUCTION: Neural oscillations and the parametrized 1/f slope of the power spectrum are increasingly recognized as biomarkers of brain function, both potentially reflecting the local excitation-inhibition balance. While gamma-band synchrony is crucial for local circuit coordination, its relationship with the spectral slope remains poorly understood.

AIM(S): This study investigates whether the spectral exponent relates to stimulus-driven gamma synchronization during 40-Hz auditory steady-state responses (ASSR).

METHOD(S): We re-analyzed magnetoencephalography (MEG) data from 15 healthy participants during 40-Hz auditory stimulation, extracting spectral parameters (exponent and offset) and inter-trial phase coherence (ITPC) across 148 cortical regions. Using Bayesian multilevel regression with crossed subject and ROI random effects, we modeled both prestimulus and stimulus periods jointly to test the condition by exponent interaction on ITPC.

RESULTS: Auditory stimulation increased ITPC in auditory and temporal regions but did not alter the spectral exponent or offset. A positive relationship between spectral exponent and ITPC emerged during stimulation: steeper slopes were associated with stronger phase-locking to the 40-Hz stimulus, with this effect strongest in regions showing robust ASSR responses. Strong collinearity between exponent and offset limits our ability to disentangle exponent-specific effect.

CONCLUSIONS: These findings suggest that steeper slopes, potentially reflecting greater inhibitory influence, may provide the temporal scaffolding for precise neural synchronization with biological interpretation linked to excitation-inhibition balance, though methodological confounding in phase estimation cannot be ruled out. Integrated spectral and oscillatory measures may provide more sensitive markers of local circuit integrity than either measure alone.