Exogenously Driven Neural Reactivation of Spatially Matching Visual Working-Memory Contents.

Selective attention is often divided into voluntary (goal-directed) and involuntary (stimulus-driven) forms, a distinction extensively studied for attention to external sensory input. In contrast, internal selective attention-directed toward representations held in working memory (WM)-has been considered primarily for voluntary influences. Recent behavioral evidence suggests that task-irrelevant external stimuli can also influence internal selection of feature-matching WM representations involuntarily, yet the neural mechanisms underlying these effects remain unclear. Here, we tested whether an uninformative exogenous spatial retro-cue presented during a WM delay can act as a selective "ping" and reactivate spatially matching WM content at the level of its representational category. Male and female human participants memorized complex contents presented at distinct locations, followed by unpredictive and task-irrelevant spatial retro-cues that conveyed no category information. Using temporally resolved multivariate electroencephalography decoding, we observed category-specific reactivation of spatially matching WM representations following these cues, providing direct neural evidence for stimulus-driven, involuntary attentional selection within WM, ahead of the memory test. Moreover, neural responses to the subsequent memory-probe were also modulated by cue congruency, consistent with the notion that exogenous influences begin early during sensory processing while also shaping later decision-related processes. Finally, drift diffusion model analyses revealed that this involuntary cueing effect was primarily driven by increased evidence accumulation. Together, these findings illuminate the mechanisms by which external events can automatically and involuntarily penetrate the internal cognitive workspace.