The cortical N1 response to balance perturbation is observed in electroencephalography recordings simultaneous to automatic balance-correcting muscle activity. We recently observed larger cortical N1s in individuals who had greater difficulty resisting compensatory steps, suggesting the N1 may be influenced by stepping or changes in response strategy. Here, we test whether the cortical N1 response is influenced by stepping (planned steps vs. feet-in-place) or prior planning (planned vs. unplanned steps). We hypothesized that prior planning of a step would reduce the amplitude of the cortical N1 response to balance perturbations. In 19 healthy young adults (11 female, ages 19-38) we measured the cortical N1amplitude evoked by 48 backward translational support-surface perturbations of unpredictable timing and amplitude in a single experimental session. Participants were asked to plan a stepping reaction on half of perturbations, and to resist stepping otherwise. Perturbations included an easy (8 cm, 16 cm/s) perturbation that was identical across participants and did not naturally elicit compensatory steps, and a height-adjusted difficult (18-22 cm, 38-42 cm/s) perturbation that frequently elicited compensatory steps despite instructions to resist stepping. In contrast to our hypothesis, cortical N1 response amplitudes did not differ between planned and unplanned stepping reactions, but cortical responses were 11% larger with the execution of planned compensatory steps compared to nonstepping responses to difficult perturbations. These results suggest a possible role for the cortical N1 in the execution of compensatory steps for balance recovery, and this role is not influenced by whether the compensatory step was planned before the perturbation.

中文翻译：

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平衡扰动诱发的皮层 N1 反应在踏步时更大，不受运动计划的影响

在自动平衡校正肌肉活动的同时，在脑电图记录中观察到皮质 N1 对平衡扰动的反应。我们最近观察到在抵抗补偿性步骤更困难的个体中较大的皮质 N1，表明 N1 可能受到步进或响应策略变化的影响。在这里，我们测试皮层 N1 反应是否受步进（计划步骤与足部原位）或先前计划（计划与计划外步骤）的影响。我们假设预先计划一个步骤会降低皮层 N1 对平衡扰动的反应幅度。在 19 名健康的年轻人中（11 名女性，19-38 岁）我们测量了由 48 个不可预测的时间和幅度的反向平移支撑表面扰动在单个实验过程中引起的皮质 N1 幅度。参与者被要求计划对一半的扰动进行踩踏反应，否则拒绝踩踏。扰动包括一个简单的（8 厘米，16 厘米/秒）扰动，在参与者之间是相同的，不会自然引起补偿步骤，以及高度调整的困难（18-22 厘米，38-42 厘米/秒）经常引起的扰动尽管有拒绝踩踏的指示，但仍采取补偿措施。与我们的假设相反，皮层 N1 反应幅度在计划和计划外的踏步反应之间没有差异，但是与对困难扰动的非步进响应相比，执行计划的补偿步骤的皮质响应高 11%。这些结果表明皮质 N1 在执行平衡恢复的补偿步骤中可能发挥作用，并且该作用不受是否在扰动之前计划补偿步骤的影响。