Adjustments of balance control during cognitive dual tasking: Evidence from event-related force-plate analysis

Cognitive-motor interference refers to the interaction between cognitive and motor processes occurring at the same time. Recently, balance control parameters while standing on a force plate were analysed using an event-related approach while participants performed a Simon task. Resolving response conflict in incongruent trials reduced balance adjustments prior to manual response execution, suggesting a bottleneck for concurrent cognitive and balance control. In the present study, we combined this approach with a cognitive dual task which comprised a visual-vocal short-term memory task with a delayed vocal response and an auditory-manual reaction time (RT) task. This hybrid psychological refractory period (PRP) paradigm created a functional processing bottleneck during memory consolidation in the visual-vocal short-term memory task. To examine how this cognitive bottleneck influences balance control, 48 participants per experiment stood quietly on a force plate, and balance control was quantified as moment variability (mN·m) in 100 ms sliding windows. We varied the stimulus-onset asynchrony (SOA: 100 vs. 1,000 ms) between the targets (Experiment 1) and task load (report vs. ignore the visual object; Experiment 2). As expected, auditory-manual RTs increased at short SOA, showing dual-task interference that persisted in ignore trials, consistent with task-set inertia. Force-plate data were analysed using cluster permutation analysis to identify time-specific effects. Participants were less likely to adjust balance during cognitive task processing and more likely after task completion, independent of the presence of a cognitive bottleneck. These findings suggest that balance control flexibly delays or advances balance adjustments based on cognitive demands, thereby reducing cognitive-motor interference. PUBLIC SIGNIFICANCE STATEMENT: This study shows that when people are performing demanding cognitive tasks, such as remembering information while responding to auditory signals, balance adjustments can be temporarily reduced or altered, particularly when the cognitive tasks are difficult. These findings highlight the interaction of cognitive tasks and balance and specifically provide insights into how cognitive processes influence stability during standing. Our understanding of the mechanisms linking cognition and balance may guide future studies on how such interactions change with age or cognitive impairment.