Neural Evidence for an Object-based Pointer System Underlying Working Memory

To accomplish even rudimentary tasks, our cognitive system must update its representation of the changing environment. This process relies on visual working memory (VWM), which can actively modify its representations. We argue that this ability depends on a pointer system, such that each representation is stably and uniquely mapped to a specific stimulus. Without these pointers, VWM representations are inaccessible and therefore unusable. In three Electroencephalogram (EEG) experiments, we examined whether the pointers are allocated in an object-based, featural, or spatial manner: three factors that were confounded in previous studies. We used a feature change-detection task, in which objects moved and could separate into independently-moving parts. Despite the movement and separation being completely task-irrelevant, we found that the separation invalidated the pointers. This happened in a shape task, where the separation changed both the objects and the task-relevant features, but importantly, also in a color task, where the separation destroyed the objects while leaving the task-relevant features intact. Furthermore, even in a color task where all items had identical shapes, object-separation invalidated the pointers. This suggests that objects and not task-relevant features underlie the pointer system. Finally, when each object-part could be individuated already before the separation, the pointers were maintained, suggesting that the pointers are specifically tied to objects rather than locations. These results shed new light on the pointers which underlie VWM performance, demonstrating that the pointer system is object-based regardless of the task requirements.