Relationships Between Spontaneous Alpha Oscillation and Brain Response Amid the Complexity of Brain Adaptation and Spectral Signal Composition.

The brain operates as a complex dynamic system, continuously generating both structured spontaneous activity and stimulus-evoked responses. Because these activities originate from the same neural architecture, they are hypothesized to be interconnected. However, research has yet to establish a definitive relationship between spontaneous and response patterns, as findings have been mixed and inconclusive. We argue that this ambiguity stems from significant theoretical and methodological challenges in characterizing the relevant variables amidst the brain's complexity. In this study, we investigated the cross-individual correlation between spontaneous Alpha amplitude and the magnitude of brain responses to simple stimuli. Our analysis revealed a robust correlation, but only after accounting for two key confounding factors inherent to the brain's complex dynamics: (1) strong adaptation effects across repeated stimulus exposures and (2) the mixture of aperiodic and band-specific dynamic activity signals. These results demonstrate a close association between the strength of Alpha oscillations-a primary brain rhythm implicated in various functions-and the magnitude of stimuli-evoked responses. Specifically, individuals with higher resting-state Alpha amplitudes exhibit stronger brain responses. This discovery not only highlights methodological challenges in relating spontaneous and evoked brain activity, but also demonstrates that they can be addressed. Our findings have significant implications for research aimed at understanding the mechanistic models and functional roles of the brain's dynamic system, shedding light on future investigations into the interplay between intrinsic and evoked neural dynamics.