The effect of occlusion on the visual working memory pointer-system.

Abstract

To access its online representations, visual working memory (VWM) relies on a pointer-system that creates correspondence between objects in the environment with their memory representations. This pointer-system allows VWM to modify its representations using a process called updating. When the pointer is invalidated, however, VWM triggers a process called resetting in which the no longer relevant representation and pointer are replaced. Past studies used the contralateral delay activity (CDA) to differentiate between updating and resetting and found that resetting is followed by a drop in the CDA amplitude. The current study aimed to investigate the effects of occlusion on VWM representations and the resetting process across four experiments. Experiment 1 examined whether resetting occurs with occluded changes and compared the CDA of occluded versus visible objects. The results indicated a decline in CDA amplitude during occlusion, but it was unclear if resetting occurred when the change was occluded due to the lack of time-locked changes. To better isolate the resetting process, Experiment 2 used a brief occluder appearances (100 ms) and observed a CDA drop likely due to an ERP response to the sudden stimulus appearance. This drop occurred earlier than the resetting CDA drop and appeared even in conditions that did not trigger resetting, which indicates that it might be an ERP response to the short and sudden appearance of a stimulus. Experiment 3 further isolated this ERP response, confirming the early CDA drop as a reaction to the occluder's onset and offset. Experiment 4, which included occluders that did not flash to avoid ERP responses, found a CDA drop indicating that resetting can occur with inferred changes. These findings suggest that VWM maintains representations of occluded objects, and can update or reset these representations based on inferred changes, with brief stimuli eliciting ERP responses that affect CDA amplitude.