Task-irrelevant features in working memory alter current visual processing

Higher-level cognition depends on visual working memory (VWM), the ability of our brain to maintain and manipulate internal representations of images that are no longer presented to us. An important question in this field is whether VWM is represented in a sensory or nonsensory manner. Progress has been made in understanding the features to be remembered, but the representational nature of the memory-irrelevant features is unclear. Here, we used a dual-task paradigm to investigate how and when the memory-irrelevant features interact with the concurrent visual information. In a series of experiments, participants were asked to perform a visual search task (Experiment 1) or a perceptual discrimination task (Experiments 2 and 3) involving a memory- irrelevant feature while simultaneously holding the other feature for later retrieval. Experiment 1 showed that VWM biases the allocation of attention to color matching to the memory-irrelevant color. More importantly, the degree of VWM-biased attention decreased monotonically with decreasing feature similarity, and this behavioral monotonic gradient profile resembled the tuning curve of feature-selective neurons in the early visual cortex. Experiment 2 revealed that irrelevant features biased ongoing perception, as indicated by the shifted discrimination threshold. Experiment 3 further demonstrated that VWM-biased perception occurs only at short delays but not at prolonged delays. Our results suggest that the memory-irrelevant feature is represented as a sensory analog for a limited period of time in the visual areas where it was initially processed. Our results extend sensory recruitment theory to memory-irrelevant features in VWM.