TACTUAL DISCRIMINATION OF SOFTNESS
TACTUAL DISCRIMINATION OF SOFTNESS
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DOI：
10.1152/jn.1995.73.1.88
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发表时间：
1995-01-01
影响因子：
2.5
通讯作者：
LAMOTTE, RH
中科院分区：
文献类型：
--
作者：
SRINIVASAN, MA;LAMOTTE, RH
1。我们研究了人类使用具有可变形且刚性表面的新型弹性对象来触发物体柔软度的能力。对于具有变形表面的对象，我们施放具有可变合适的透明橡胶样本。对于具有刚性表面（“弹簧细胞”）的物体，我们用内部圆柱体制造了望远镜的空心圆柱体，并由几个弹簧支撑。为了衡量人类的可区分性并隔离相关的信息进化机制，我们在三个条件下进行了心理物理实验：1）与正常的手指进行主动接触，在该手指上均可使用触觉和动觉信息； 2）与局部皮肤麻醉的主动触摸，因此只有动力学信息可用； 3）被动触摸，在该触摸中，计算机控制的机械刺激器将兼容的标本降低到了受试者的被动指纹上，因此，他们只有触觉信息。2。我们首先通过确定刚性探针在恒定凹痕期间的深度和凹痕力之间的关系来表征人指的机械行为和测试对象的机械行为。 FingerPad在压痕深度与力痕迹中表现出明显的非线性行为，使得符合性（如迹线的局部斜率所示）。随着压痕深度的增加而减少。所有橡胶样品的迹线大致是线性的，表明每个标本的依从性恒定但独特的值。指鱼比每个橡胶标本都更合规。3。所有人类受试者在通过主动触摸对橡胶标本进行排名时表现出极好的柔软性可区分性，而对柔软度的主观感知与客观测量的依从性一对一相关。与橡胶试样相比，受试者区分春季细胞依从性的能力始终较差。4。为了对选定的一组橡胶标本进行成对歧视，仅动力学信息是不够的。但是，即使施用样品的速度和力是随机分配的，仅触觉信息就足够了。相比之下，对于区分春季细胞对，仅触觉信息是不够的，并且发现触觉和动觉信息都是必要的。5。触觉信息的充分性差异可以通过指纹接触的机制及其对触觉信息的影响来解释两种类型的物体。对于具有变形表面的物体，接触区域内的空间压力分布取决于施加的力和样品依从性。因此，对于给定的净力，皮肤变形取决于标本的依从性，触觉信息能够编码具有变形表面的对象的合规性。对于具有刚性表面的合规物体，给定净力的压力分布和皮肤变形独立于物体合规性，因此仅触觉信息就不足以编码其合规性。
1. We investigated the ability of humans to tactually discriminate the softness of objects, using novel elastic objects with deformable and rigid surfaces. For objects with deformable surfaces, we cast transparent rubber specimens with variable compliances. For objects with rigid surfaces (''spring cells'') we fabricated telescoping hollow cylinders with the inner cylinder supported by several springs. To measure the human discriminability and to isolate the associated information-procressing mechanisms, we performed psychophysical experiments under three conditions: 1) active touch with the normal finger, where both tactile and kinesthetic information was available to the subject; 2) active touch with local cutaneous anesthesia, so that only kinesthetic information was available; and 3) passive touch, where a computer-controlled mechanical stimulator brought down the compliant specimens onto the passive fingerpad of the subject, who therefore had only tactile information.2. We first characterized the mechanical behavior of the human fingerpad and the test objects by determining the relationship between the depth and force of indentation during constant-velocity indentations by a rigid probe. The fingerpad exhibited a pronounced nonlinear behavior in the indentation depth versus force trace such that compliance, as indicated by the local slope of the trace. decreased with increases in indentation depth. The traces for all the rubber specimens were approximately linear, indicating a constant but distinct value of compliance for each specimen. The fingerpad was more compliant than each of the rubber specimens.3. All the human subjects showed excellent softness discriminability in ranking the rubber specimens by active touch, and the subjective perception of softness correlated one-to-one with the objectively measured compliance. The ability of subjects to discriminate the compliance of spring cells was consistently poorer compared with that of the rubber specimen's.4. For pairwise discrimination of a selected set of rubber specimens, kinesthetic information alone was insufficient. However, tactile information alone was sufficient, even when the velocities and forces of specimen application were randomized. In contrast, for discriminating pairs of spring cells, tactile information alone was insufficient, and both tactile and kinesthetic information were found to be necessary.5. The differences in the sufficiency of tactile information for the discrimination of the two types of objects can be explained by the mechanics of contact of the fingerpad and its effect on tactile information. For objects with deformable surfaces, the spatial pressure distribution within the contact region depends on both the force applied and the specimen compliance. Consequently, for a given net force, skin deformation is dependent on specimen compliance and tactile information is able to encode the compliance of objects with deformable surfaces. For compliant objects with rigid surfaces, the pressure distribution and skin deformation for a given net force are independent of object compliance and therefore tactile information alone is not sufficient to encode their compliance.