Contralateral Hand and Foot Know the Time Better: Advantages in Temporal Order Judgment and Their Processing Stages

In real-world scenarios, coordination between the contralateral hand and foot is often required to accomplish basic motor tasks, such as walking or running. Research on active movement has shown that the contralateral hand and foot perform better than the ipsilateral hand and foot in terms of interlimb coordination. However, whether this contralateral advantage extends to passive temporal perception remains unknown. In this study, the contralateral advantage was investigated via a temporal order judgment task using ERP technology. The participants received two sequential tactile stimuli on one hand and one foot and determined whether the sequence was "hand before foot" or "foot before hand." The behavioral results revealed a contralateral advantage in temporal order judgment. Responses to stimuli on the contralateral hand and foot had greater accuracy rates, faster RTs, and smaller just-noticeable differences. The advantage of RTs was modulated by crossing the limbs but remained intact for right-hand responses. The ERP results exhibited a similar pattern, with earlier centroparietal positivity latency and reduced centroparietal positivity and P1 peaks for the contralateral hand and foot combinations. The results indicate a temporal judgment advantage for contralateral hand and foot combinations in both the early and late stages of temporal processing. These findings elucidated the behavioral and neural mechanisms underlying the superior interlimb coordination observed for the contralateral hand and foot combination, with implications for future research to improve the treatment of movement disorders in patient populations.