Microsaccades reveal preserved spatial organisation in visual working memory despite decay in location-based rehearsal

Space provides a foundational scaffold for retaining and selecting visual information in working memory. It remains unclear, however, whether and how spatial organisation in visual working memory persists over temporally extended memory delays, particularly when the locations of memoranda are incidental and never probed for report. Studies using continuous spatial markers of working-memory retention often report a gradual decay over time, which may or may not reflect a genuine decay in spatial organisation within working memory. To examine this, we capitalised on two recently established spatial eye-movement (microsaccade) markers of 'location-based mnemonic rehearsal' and 'location-based mnemonic selection' that we here studied during and following short (1 s), medium (3 s), and long (5 s) working-memory delays. Our findings, replicated across two experiments, demonstrate that while markers of location-based rehearsal may diminish throughout the working-memory delay, mnemonic selection remains anchored to incidentally encoded object locations. This implies that spatial organisation in working memory is preserved even when markers of active spatial rehearsal have meanwhile decayed, suggesting the notion of a "silent spatial scaffold" for working memory.