Sozzi Stefania, Decortes Francesco, Schmid Monica, Crisafulli Oscar, Schieppati Marco
Centro Studi Attività Motorie, Istituti Clinici Scientifici Maugeri, Pavia, Italy.
Centro di Riabilitazione Visiva, Istituti Clinici Scientifici Maugeri, Pavia, Italy.
Front Neurosci. 2018 Sep 11;12:639. doi: 10.3389/fnins.2018.00639. eCollection 2018.
Subjects with low vision often use a cane when standing and walking autonomously in everyday life. One aim of this study was to assess differences in the body stabilizing effect produced by the contact of the cane with the ground or by the fingertip touch of a firm surface. Another aim was to estimate the promptness of balance stabilization (or destabilization) on adding (or withdrawing) the haptic input from cane or fingertip. Twelve blind subjects and two subjects with severe visual impairment participated in two experimental protocols while maintaining the tandem Romberg posture on a force platform. In one protocol, subjects lowered the cane to a second platform on the ground and lifted it in sequence at their own pace. In the other protocol, they touched an instrumented pad with the index finger and withdrew the finger from the pad in sequence. In both protocols, subjects were asked to exert a force not granting mechanical stabilization. Under steady-state condition, the finger touch or the contact of the cane with the ground significantly reduced (to ∼78% and ∼86%, respectively) the amplitude of medio-lateral oscillation of the centre of foot pressure (CoP). Oscillation then increased when haptic information was removed. The delay to the change in body oscillation after the haptic shift was longer for addition than withdrawal of the haptic information (∼1.4 s and ∼0.7 s, respectively; < 0.001), but was not different between the two haptic conditions (finger and cane). Similar stabilizing effects of input from cane on the ground and from fingertip touch, and similar latencies to integrate haptic cue from both sources, suggest that the process of integration of the input for balance control is initiated by the haptic stimulus at the interface cane-hand. Use of a tool is as helpful as the fingertip input, and does not produce different stabilization. Further, the latencies to haptic cue integration (from fingertip or cane) are similar to those previously found in a group of sighted subjects, suggesting that integration delays for automatic balance stabilization are not modified by visual impairment. Haptic input from a tool is easily exploited by the neural circuits subserving automatic balance stabilization in blind people, and its use should be enforced by sensory-enhancing devices and appropriate training.
视力低下的受试者在日常生活中自主站立和行走时经常使用手杖。本研究的一个目的是评估手杖与地面接触或指尖触摸坚硬表面所产生的身体稳定效果的差异。另一个目的是估计在添加（或撤回）来自手杖或指尖的触觉输入时平衡稳定（或不稳定）的及时性。12名盲人受试者和2名严重视力障碍受试者在测力平台上保持串联罗姆伯格姿势参与了两个实验方案。在一个方案中，受试者将手杖降低到地面上的第二个平台，并按照自己的节奏依次抬起。在另一个方案中，他们用食指触摸一个装有仪器的垫子，并依次将手指从垫子上移开。在两个方案中，都要求受试者施加不给予机械稳定的力。在稳态条件下，手指触摸或手杖与地面的接触显著降低了（分别降至约78%和约86%）足底压力中心（CoP）的中外侧振荡幅度。当触觉信息被移除时，振荡随后增加。触觉信息添加时身体振荡变化的延迟比撤回时更长（分别约为1.4秒和约0.7秒；P<0.001），但在两种触觉条件（手指和手杖）之间没有差异。手杖与地面接触的输入和指尖触摸的输入具有相似的稳定效果，并且从这两种来源整合触觉线索的潜伏期相似，这表明用于平衡控制的输入整合过程是由手杖-手界面处的触觉刺激启动的。使用工具与指尖输入一样有帮助，并且不会产生不同的稳定性。此外，触觉线索整合的潜伏期（来自指尖或手杖）与之前在一组有视力的受试者中发现的相似，这表明自动平衡稳定的整合延迟不会因视力障碍而改变。盲人中用于自动平衡稳定的神经回路很容易利用来自工具的触觉输入，并且应该通过感官增强设备和适当的训练来加强其使用。
