Fig. 3: Age-related changes in bilateral KS and MS symmetry.

To assess changes in the bilateral symmetry of synergies across the lifespan, KMSs from the left and right lower limbs were aligned for each subject and stage by maximizing Pearson correlation, after which the similarity of the corresponding KSs and MSs were calculated. A, B Population means of bilateral KS and MS similarity across six stages (n = 9, 9, 10, 11, 7, 7) are shown with error bars, with statistically significant differences between stages indicated above the bars (red: p < 0.001; blue: p < 0.05). For both KS and MS, bilateral symmetry increased significantly throughout the infantile stages, reaching its peak in adulthood. C, D Bilateral similarities in KS and MS were regressed on the subject’s age (in days, log10-transformed, n = 52) using a quadratic model. The fitted formula, root mean squared error (RMSE), and p-value for the whole model are provided in each subplot.