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 to 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 post-cue) 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. Significance statement Our study provides novel evidence of the dynamic nature of involuntary, reflexive attention, contributing to an ongoing debate about the mechanisms of exogenous spatial attention. By employing advanced neuroimaging techniques, we demonstrate that attentional gradients can flexibly adapt to cue characteristics, revealing a more nuanced understanding of how attention is allocated during rapid, involuntary shifts of focus. These findings extend the zoom lens model beyond voluntary attention, highlighting the brain's sophisticated mechanisms of spatial attention