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 EEG 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.<b>Significance Statement</b> The processes underlying involuntary attentional selection of internal information held in our working-memory system have been largely overlooked. Our study shows that external stimuli can automatically select information that is temporarily held in our mind. We found that uninformative, task-irrelevant visual cues can selectively "ping" and reactivate specific working-memory contents, despite carrying only spatial information. We demonstrate that these cues trigger category-specific neural reactivation and shape later decision-making by accelerating evidence accumulation. This extends current knowledge on how the outside world can transiently interact with our internal cognitive workspace.