Maintenance of Bound or Independent Features in Visual Working Memory is Taskdependent

Abstract

Conflicting findings exist regarding whether features of an object are stored separately or bound together in visual working memory. This controversy is based on an implicit assumption about a default, or fixed, mode of working memory storage. In contrast, here we asked whether the anticipated task might determine the format in which information is maintained in working memory, consistent with its task-oriented function. To test this flexible maintenance hypothesis, we recorded EEG while subjects performed a delayed (Yes/No) recognition task with different requirements and loads. Across three experiments, we compared event-related potentials (ERPs) in conditions with and without the necessity of maintaining conjunctions between features, while controlling for differences in visual stimulation. In Experiment 1 (N=24), involving color-location conjunctions, we identified a delay-period effect characterized by a positive potential shift in central-parietal channels when conjunction was not required by the task. This pattern, distinct from the effect caused by an increased working memory load, was confirmed in Experiment 2 (N=23) with an independent group of subjects using a similar paradigm, while also controlling for the physical appearance of probes. Finally, the observation of color and location conjunction in Experiments 1 and 2 was extended to Color and Orientation conjunction in Experiment 3 (N=22). Collectively, these three experiments provided reliable evidence demonstrating that the maintenance of feature conjunctions in working memory, whether spatial (location) or non-spatial (non-location), depends on the task goal. HighlightsO_LITask demands determine whether objects are represented as separate features or as conjoined items (maintenance format) in visual working memory. C_LIO_LIEEG recordings show differential activity despite similar stimulation, reflecting task demands. C_LIO_LIThe effect of the task is evident in the early stages of working memory processing. C_LIO_LIFlexibility in maintenance format was observed for both color-location and color-orientation conjunctions. C_LIO_LIThe findings challenge the notion of fixed maintenance format during visual working memory. C_LI