Alpha-Band Activity Tracks Reflexive Changes in the Breadth of the Zoom Lens of Attention.

Spatial attention is often conceptualized as a flexible "zoom lens" that can dynamically adjust its focus, but most evidence stems from studies of voluntary attention. Our study investigates whether involuntary, reflexive attention exhibits similar adaptability in attentional scope. Using behavioral and electroencephalographic (EEG) experiments with exogenous cues of varying spatial extent, we examined how attentional gradients dynamically adjust when attention is involuntarily captured. Male and female human participants performed visual search tasks preceded by narrow- or broad-cue displays at different onset asynchronies. We applied inverted encoding models to alpha-band neural activity to precisely track the locus and breadth of attentional tuning. Across experiments, we found that reflexive attentional gradients flexibly adapt to match cue characteristics. Behaviorally, narrow cues yielded progressively sharper attentional gradients compared with broad cues, with differences emerging over time. Critically, EEG analyses revealed that alpha-band activity tracked these dynamic adjustments, with differences in spatial selectivity emerging rapidly (±200 ms postcue) and continuing to evolve. Contrary to previous suggestions that involuntary attention primarily influences response efficiency, our results demonstrate that exogenous cues modulate attentional resources across the visual field at early processing stages.