Centro Studi Attività Motorie, ICS Maugeri SPA SB, IRCCS, Institute of Pavia, Pavia, Italy.
Department of Clinical-Surgical, Diagnostic and Paediatric Sciences, University of Pavia, Pavia, Italy.
PLoS One. 2020 Jul 31;15(7):e0236702. doi: 10.1371/journal.pone.0236702. eCollection 2020.
When humans are administered continuous and predictable perturbations of stance, an adaptation period precedes the steady state of balancing behaviour. Little information is available on the modulation of adaptation by vision and perturbation frequency. Moreover, performance of supra-postural tasks may modulate adaptation in as yet unidentified ways. Our purpose was to identify differences in adaptation associated to distinct visual tasks and perturbation frequencies. Twenty non-disabled adult volunteers stood on a platform translating 10 cm in antero-posterior (AP) direction at low (LF, 0.18 Hz) and high frequency (HF, 0.56 Hz) with eyes open (EO) and closed (EC). Additional conditions were reading a text fixed to platform (EO-TP) and reading a text stationary on ground (EO-TG). Peak-to-peak (PP) displacement amplitude and AP position of head and pelvis markers were computed for each of 27 continuous perturbation cycles. The time constant and extent of head and pelvis adaptation and the cross-correlation coefficients between head and pelvis were compared across visual conditions and frequencies. Head and pelvis mean positions in space varied little across conditions and perturbation cycles but the mean head PP displacements changed over time. On average, at LF, the PP displacement of the head and pelvis increased progressively. Adaptation was rapid or ineffective with EO, but slower with EO-TG, EO-TP, EC. At HF, the head PP displacement amplitude decreased progressively with fast adaptation rates, while the pelvis adaptation was not apparent. The results show that visual tasks can modulate the adaptation rate, highlight the effect of the perturbation frequency on adaptation and provide evidence of priority assigned to pelvis stabilization over visual tasks at HF. The effects of perturbation frequency and optic flow and their interaction with other sensory inputs and cognitive tasks on the adaptation strategies should be investigated in impaired individuals and considered in the design of rehabilitation protocols.
当人体受到持续且可预测的姿势干扰时，在平衡行为的稳定状态之前会有一个适应期。关于视觉和干扰频率对适应的调节作用，目前所知甚少。此外，超姿势任务的表现可能以尚未确定的方式调节适应。我们的目的是确定与不同视觉任务和干扰频率相关的适应差异。二十名非残疾成年志愿者站在一个平台上，以 0.18 Hz（低频，LF）和 0.56 Hz（高频，HF）的频率在前后（AP）方向平移 10 cm，同时眼睛睁开（EO）和闭眼（EC）。其他条件包括阅读固定在平台上的文本（EO-TP）和阅读地面上固定的文本（EO-TG）。对于每个连续的 27 个干扰周期，计算头和骨盆标记的峰峰值（PP）位移幅度和 AP 位置。比较了视觉条件和频率下的头部和骨盆适应的时间常数和程度以及头部和骨盆之间的互相关系数。头和骨盆在空间中的平均位置在各条件和干扰周期之间变化很小，但头的平均 PP 位移随时间变化。平均而言，在 LF 时，头和骨盆的 PP 位移逐渐增加。EO 时适应迅速或无效，但 EO-TG、EO-TP 和 EC 时较慢。在 HF 时，头部 PP 位移幅度逐渐减小，适应率较快，而骨盆适应不明显。结果表明，视觉任务可以调节适应率，突出了干扰频率对适应的影响，并为在 HF 时骨盆稳定优先于视觉任务提供了证据。应该在受损个体中研究干扰频率和光流及其与其他感觉输入和认知任务的相互作用对适应策略的影响，并在康复方案的设计中考虑这些影响。
