Yoojeong Choo¹, Weiwei Zhang², Weizhen Xie¹; ¹University of Maryland, College Park, ²University of California, Riverside

Simple physical actions, such as sustained handgrip, impose measurable cognitive costs on visual processing, impairing visual attention and working memory (VWM). Yet the mechanisms underlying this action-cognition trade-off are not well understood. Here, we used a change-detection task paired with concurrent handgrip, manipulating physical load (low vs. high) and the presence of task-irrelevant distractors, to examine two plausible impacts of physical exertion on VWM. One possibility is that action and cognition draw on shared resources, such that engaging the motor system reduces one’s ability to actively retain visual information. Another possibility is that physical exertion places demands on executive control, particularly the ability to suppress distractors, without directly reducing the retention of task-relevant content. Across two experiments, concurrent physical load impaired VWM behavioral performance, particularly in the presence of distractors. In Experiment 1 (n = 20), EEG results showed that stronger concurrent handgrip force did not reliably reduce the contralateral delay activity (CDA), a neural marker associated with maintained VWM items, providing limited evidence for the retention cost account. Instead, higher physical load was associated with increased CDA amplitude when distractors were present, consistent with greater intrusion of task-irrelevant information into VWM during physical exertion. In Experiment 2 (n = 20), fMRI revealed engagement of bilateral inferior frontal and left posterior parietal cortices – regions previously implicated in both cognitive and motor inhibitory control processes – when physical load and visual distractors co-occurred. Taken together, these findings indicate that the cognitive costs of physical exertion arise not from depletion of a shared representational resource, but potentially from reduced inhibitory control that allows distractors to intrude into VWM. As inhibitory control emerges as a potential bottleneck for visual cognition under physical strain, future research should further elucidate how this bottleneck is implemented within, and potentially modulated through, frontoparietal network dynamics.