An investigation of the mechanics of tactile sense using two-dimensional models of the primate fingertip
An investigation of the mechanics of tactile sense using two-dimensional models of the primate fingertip
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DOI：
10.1115/1.2795945
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发表时间：
1996-02-01
影响因子：
1.7
通讯作者：
Dandekar, K
中科院分区：
文献类型：
--
作者：
Srinivasan, MA;Dandekar, K
关于与皮肤表面接触的物体的触觉信息包含在皮肤上的时空负荷分布、皮肤内的机械敏感感受器位置处的相应应力和应变以及由感受器群体产生的电脉冲的相关模式中。目前，虽然可以记录受体对已知刺激的反应，但还没有实验技术来观察皮肤上的负荷分布或受体位置处的相应应力状态。在本文中，力学的触觉信息的神经编码的作用进行了研究，使用简单的灵长类动物指尖模型。四个模型，从一个半无限介质的几何形状范围内的一个圆柱形手指与刚性骨，并组成的线弹性介质，在平面应变条件下，使用有限元法进行了分析。结果表明，模型的几何形状有显着的影响，表面载荷分布以及亚表面的应力和应变场为一个给定的机械刺激。弹性介质的作用类似于空间低通滤波器，其特性是感受器位置越深，触觉信息越模糊。没有一个模型预测了实验观察到的线下表面偏转轮廓，与将指垫视为包裹不可压缩流体的膜的简单非均质水床模型（Srinivasan，1989年）一样接近。然而，这种水床模型预测了指尖内部的均匀压力状态，因此无法解释在神经反应中观察到的空间变化。对于圆柱形模型缩进矩形光栅，最大压缩应变和应变能量密度在典型的受体位置出现的两个应变措施，直接关系到电生理记录的反应速率的慢适应I型（SAI）mechanoreceptors。应变能密度是SAI的相关刺激的更好候选者，因为它是相对于受体取向不变的标量，并且是由施加在皮肤上的负载引起的受体变形的直接测量。
Tactile information about an object in contact with the skin surface is contained in the spatio-temporal load distribution on the skin, the corresponding stresses and strains at mechanosensitive receptor locations within the skin, and the associated pattern of electrical impulses produced by the receptor population. At present, although the responses of the receptors to known stimuli can be recorded, no experimental techniques exist to observe either the load distribution on the skin or the corresponding stress-state at the receptor locations. In this paper, the role of mechanics in the neural coding of tactile information is investigated using simple models of the primate fingertip. Four models that range in geometry from a semi-infinite medium to a cylindrical finger with a rigid bone, and composed of linear elastic media, are analyzed under plane strain conditions using the finite element method. The results show that the model geometry has a significant influence on the surface load distribution as well as the subsurface stress and strain fields for a given mechanical stimulus. The elastic medium acts like a spatial low pass filter with the property that deeper the receptor location, the more blurred the tactile information. None of the models predicted the experimentally observed surface deflection profiles under line lends as closely as a simple heterogeneous waterbed model that treated the fingerpad as a membrane enclosing an incompressible fluid (Srinivasan, 1989). This waterbed model, however, predicted a uniform state of stress inside the fingertip and thus failed to explain the spatial variations observed in the neural response. For the cylindrical model indented by rectangular gratings, the maximum compressive strain and strain energy density at typical receptor locations emerged as the two strain measures that were directly related to the electrophysiologically recorded response rate of slowly adapting type I(SAI) mechanoreceptors. Strain energy density is a better candidate to be the relevant stimulus for SAIs, since it is a scalar that is invariant with respect to receptor orientations and is a direct measure of the distortion of the receptor caused by the loads imposed on the skin.