Bilaloglu Seda, Lu Ying, Geller Daniel, Rizzo John Ross, Aluru Viswanath, Gardner Esther P, Raghavan Preeti
Department of Rehabilitation Medicine, New York University School of Medicine, New York, New York;
Center for the Promotion of Research Involving Innovative Statistical Methodology, Steinhardt School of Culture, Education and Human Development, New York University, New York, New York;
J Neurophysiol. 2016 Mar;115(3):1122-31. doi: 10.1152/jn.00639.2015. Epub 2015 Dec 9.
Adaptation of fingertip forces to friction at the grasping surface is necessary to prevent use of inadequate or excessive grip forces. In the current study we investigated the effect of blocking tactile information from the fingertips noninvasively on the adaptation and efficiency of grip forces to surface friction during precision grasp. Ten neurologically intact subjects grasped and lifted an instrumented grip device with 18 different frictional surfaces under three conditions: with bare hands or with a thin layer of plastic (Tegaderm) or an additional layer of foam affixed to the fingertips. The coefficient of friction at the finger-object interface of each surface was obtained for each subject with bare hands and Tegaderm by measuring the slip ratio (grip force/load force) at the moment of slip. We found that the foam layer reduced sensibility for two-point discrimination and pressure sensitivity at the fingertips, but Tegaderm did not. However, Tegaderm reduced static, but not dynamic, tactile discrimination. Adaptation of fingertip grip forces to surface friction measured by the rate of change of peak grip force, and grip force efficiency measured by the grip-load force ratio at lift, showed a proportional relationship with bare hands but were impaired with Tegaderm and foam. Activation of muscles engaged in precision grip also varied with the frictional surface with bare hands but not with Tegaderm and foam. The results suggest that sensitivity for static tactile discrimination is necessary for feedforward and feedback control of grip forces and for adaptive modulation of muscle activity during precision grasp.
指尖力适应抓握表面的摩擦力对于防止使用不足或过大的握力是必要的。在当前的研究中，我们调查了无创阻断来自指尖的触觉信息对精确抓握过程中握力适应表面摩擦力及其效率的影响。10名神经系统健全的受试者在三种条件下抓握并提起一个装有仪器的握力装置，该装置有18种不同的摩擦表面：裸手抓握，或指尖贴有一层薄塑料（泰德皮肤贴膜），或额外贴有一层泡沫。通过测量每个表面在裸手和贴有泰德皮肤贴膜时滑动瞬间的滑动率（握力/负载力），为每个受试者获取手指与物体界面处的摩擦系数。我们发现，泡沫层降低了指尖两点辨别能力和压力敏感性，但泰德皮肤贴膜没有。然而，泰德皮肤贴膜降低了静态触觉辨别能力，但未降低动态触觉辨别能力。通过峰值握力变化率测量的指尖握力对表面摩擦力的适应，以及通过提起时的握力-负载力比测量的握力效率，在裸手时呈现比例关系，但在使用泰德皮肤贴膜和泡沫时受到损害。参与精确抓握的肌肉激活在裸手时也随摩擦表面而变化，但在使用泰德皮肤贴膜和泡沫时则不然。结果表明，静态触觉辨别敏感性对于握力的前馈和反馈控制以及精确抓握过程中肌肉活动的适应性调节是必要的。
