Three-ball cascade juggling as a paradigm to study complex motor task execution using mobile brain–body imaging (EEG)

Mobile brain-body imaging (MoBI) using EEG and motion capture allows us to study brain activity during natural tasks. While MoBI research has focused on gait and walking, we introduce three-ball cascade juggling as a new paradigm to explore sensorimotor brain dynamics. Successful juggling depends on tracking ball trajectories to guide motor planning. Since jugglers emphasize the apex position during learning, we hypothesized that trial-to-trial variations in apex position relate to brain activity, particularly in superior parietal regions involved in spatial attention. Our findings support this: variations in apex position correlated with 10-15 Hz alpha and low beta power in sources compatible with superior parietal cortex. The precise frequency band and timing varied across the three spatial directions. Additionally, lateral apex variations were encoded in a mirror-symmetric manner relative to the body midline. This study demonstrates the feasibility of using MoBI to investigate brain dynamics in complex motor tasks and provides insight into how the brain represents the critical ball apex position, laying the foundation for future research on its role in motor control and catch timing.