Early manifestation of arm–leg coordination during stepping on a surface in human neonates
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The accomplishment of mature locomotor movements relies upon the integrated coordination of the lower and upper limbs and the trunk. Human adults normally swing their arms and a quadrupedal limb coordination persists during bipedal walking despite a strong corticospinal control of the upper extremities that allows to uncouple this connection during voluntary activities. Here we investigated arm–leg coordination during stepping responses on a surface in human neonates. In eight neonates, we found the overt presence of alternating arm–leg oscillations, the arms moving up and down in alternation with ipsilateral lower limb movements. These neonates moved the diagonal limbs together, and the peak of the arm-to-trunk angle (i.e., maximum vertical excursion of the arm) occurred around the end of the ipsilateral stance phase, as it occurs during typical adult walking. Although episodes of arm–leg coordination were sporadic in our sample of neonates, their presence provides significant evidence for a neural coupling between the upper and lower limbs during early ontogenesis of locomotion in humans.
KeywordsNeonatal stepping Arm–leg coordination Early development Human locomotion
We thank Marika Cicchese, Nadia Dominici, Carlo Giannini, Vito Mondì and Tiziana Silei for help with some of the experiments. This work was supported by the Italian Ministry of Health (IRCCS Ricerca corrente), Italian Space Agency (contract no. I/006/06/0), Italian University Ministry (PRIN Grant 2015HFWRYY_002), Lazio Region (INNOVA.1 FILAS—RU 2014_1033), and Horizon 2020 Robotics Program (ICT-23-2014 under Grant Agreement 644727-CogIMon).
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