Lhomond Olivia, Juan Benjamin, Fornerone Theo, Cossin Marion, Paleressompoulle Dany, Prince François, Mouchnino Laurence
Aix-Marseille Université, CNRS, Laboratoire de Neurosciences Cognitives, FR 3C, Marseille, France.
Faculty of Medicine, Department of Surgery, Université de Montréal, Montreal, QC, Canada.
Front Hum Neurosci. 2021 Mar 30;15:635611. doi: 10.3389/fnhum.2021.635611. eCollection 2021.
Human adaptive behavior in sensorimotor control is aimed to increase the confidence in feedforward mechanisms when sensory afferents are uncertain. It is thought that these feedforward mechanisms rely on predictions from internal models. We investigate whether the brain uses an internal model of physical laws (gravitational and inertial forces) to help estimate body equilibrium when tactile inputs from the foot sole are depressed by carrying extra weight. As direct experimental evidence for such a model is limited, we used Judoka athletes thought to have built up internal models of external loads (i.e., opponent weight management) as compared with Non-Athlete participants and Dancers (highly skilled in balance control). Using electroencephalography, we first (experiment 1) tested the hypothesis that the influence of tactile inputs was amplified by descending cortical efferent signals. We compared the amplitude of P1N1 somatosensory cortical potential evoked by electrical stimulation of the foot sole in participants standing still with their eyes closed. We showed smaller P1N1 amplitudes in the Load compared to No Load conditions in both Non-Athletes and Dancers. This decrease neural response to tactile stimulation was associated with greater postural oscillations. By contrast in the Judoka's group, the neural early response to tactile stimulation was unregulated in the Load condition. This suggests that the brain can selectively increase the functional gain of sensory inputs, during challenging equilibrium tasks when tactile inputs were mechanically depressed by wearing a weighted vest. In Judokas, the activation of regions such as the right posterior inferior parietal cortex (PPC) as early as the P1N1 is likely the source of the neural responses being maintained similar in both Load and No Load conditions. An overweight internal model stored in the right PPC known to be involved in maintaining a coherent representation of one's body in space can optimize predictive mechanisms in situations with high balance constraints (Experiment 2). This hypothesis has been confirmed by showing that postural reaction evoked by a translation of the support surface on which participants were standing wearing extra-weight was improved in Judokas.
人类在感觉运动控制中的适应性行为旨在当感觉传入不确定时提高前馈机制的可信度。据认为，这些前馈机制依赖于内部模型的预测。我们研究当脚底的触觉输入因额外负重而受到抑制时，大脑是否使用物理定律（重力和惯性力）的内部模型来帮助估计身体平衡。由于这种模型的直接实验证据有限，我们将柔道运动员与非运动员参与者和舞者（在平衡控制方面非常熟练）进行比较，认为柔道运动员已经建立了外部负荷（即对手体重管理）的内部模型。使用脑电图，我们首先（实验1）测试了触觉输入的影响被下行皮质传出信号放大的假设。我们比较了闭眼静止站立的参与者在脚底受到电刺激时诱发的P1N1体感皮质电位的幅度。我们发现，在非运动员和舞者中，与无负荷条件相比，负荷条件下的P1N1幅度更小。这种对触觉刺激的神经反应降低与更大的姿势振荡有关。相比之下，在柔道运动员组中，负荷条件下对触觉刺激的早期神经反应没有受到调节。这表明，当触觉输入因穿着加重背心而受到机械抑制时，在具有挑战性的平衡任务中，大脑可以选择性地增加感觉输入的功能增益。在柔道运动员中，早在P1N1时右后下顶叶皮质（PPC）等区域的激活可能是负荷和无负荷条件下神经反应保持相似的来源。存储在右PPC中的超重内部模型已知参与在空间中维持身体的连贯表征，可以在高平衡约束的情况下优化预测机制（实验2）。这一假设已通过以下方式得到证实：在穿着额外重量站立的参与者所站的支撑面平移时诱发的姿势反应在柔道运动员中得到了改善。
