Ashton Graybiel Spatial Orientation Laboratory, Brandeis University, Waltham, Massachusetts.
J Neurophysiol. 2014 Mar;111(5):977-83. doi: 10.1152/jn.00927.2012. Epub 2013 Dec 4.
In a rotating environment, goal-oriented voluntary movements are initially disrupted in trajectory and endpoint, due to movement-contingent Coriolis forces, but accuracy is regained with additional movements. We studied whether adaptation acquired in a voluntary, goal-oriented postural swaying task performed during constant-velocity counterclockwise rotation (10 RPM) carries over to recovery from falling induced using a hold and release (H&R) paradigm. In H&R, standing subjects actively resist a force applied to their chest, which when suddenly released results in a forward fall and activation of an automatic postural correction. We tested H&R postural recovery in subjects (n = 11) before and after they made voluntary fore-aft swaying movements during 20 trials of 25 s each, in a counterclockwise rotating room. Their voluntary sway about their ankles generated Coriolis forces that initially induced clockwise deviations of the intended body sway paths, but fore-aft sway was gradually restored over successive per-rotation trials, and a counterclockwise aftereffect occurred during postrotation attempts to sway fore-aft. In H&R trials, we examined the initial 10- to 150-ms periods of movement after release from the hold force, when voluntary corrections of movement path are not possible. Prerotation subjects fell directly forward, whereas postrotation their forward motion was deviated significantly counterclockwise. The postrotation deviations were in a direction consistent with an aftereffect reflecting persistence of a compensation acquired per-rotation for voluntary swaying movements. These findings show that control and adaptation mechanisms adjusting voluntary postural sway to the demands of a new force environment also influence the automatic recovery of posture.
在旋转环境中,由于运动相关的科里奥利力,定向自愿运动最初在轨迹和终点处受到干扰,但通过额外的运动可以恢复准确性。我们研究了在恒定速度逆时针旋转(10 RPM)期间进行的自愿、定向姿势摆动任务中获得的适应性是否能够转移到使用保持和释放(H&R)范式从跌倒中恢复。在 H&R 中,站立的受试者主动抵抗施加在胸部的力,当力突然释放时,会导致向前跌倒并激活自动姿势矫正。我们在受试者(n = 11)进行了自愿前后摆动运动 20 次,每次 25 秒,在逆时针旋转的房间中,测试了 H&R 姿势恢复。他们脚踝周围的自愿摆动产生了科里奥利力,最初导致预期身体摆动路径的顺时针偏差,但随着每轮试验的进行,前后摆动逐渐恢复,并且在旋转后尝试前后摆动时会出现逆时针后效。在 H&R 试验中,我们检查了从保持力释放后的最初 10-150 毫秒的运动期间,此时不可能进行自愿的运动路径修正。旋转前的受试者直接向前跌倒,而旋转后的受试者的向前运动明显向逆时针方向偏离。旋转后的偏差方向与后效一致,反映了每轮自愿摆动运动获得的补偿的持久性。这些发现表明,调整自愿姿势摆动以适应新力环境的控制和适应机制也会影响姿势的自动恢复。