Representation of three dimensional shape features in somatosensory cortex

3D形状的感知依赖于手的构象和来自与手的多个接触点的刺激的整合。为了理解立体认知的神经机制，我们需要了解三件事：1)神经元如何对单个接触点的表面结构做出反应，2)皮肤不同区域的刺激是如何整合的，以及3)这种整合是如何依赖于手的构象的。这里提出的实验旨在为理解3D形状感知的这三个方面迈出第一步。目的1是确定SI和SII皮质中的神经元如何对接触单个手指的3D表面结构做出反应。这项研究将局限于手指接触刚性物体时发生的曲面曲率和边缘。3D曲面结构在平行于蒙皮曲面和垂直于蒙皮曲面的平面上变化。与目标1相关的实验将研究方向和曲率在平行于蒙皮表面的平面上变化的边和角的神经反应，以及对垂直于蒙皮表面的曲面曲率的神经反应。目的2是确定SI和SII皮质中的神经元如何对两个手指受到的刺激做出反应。缩进两个指尖的曲面根据曲面的相对运动、方向和曲率发出关于对象的不同信号。与目标2相关的实验将研究1)刺激方向和速度的影响；b)边缘方向的影响；以及c)表面曲率和斜率对相邻手指的影响。目的3是研究手指位置变化时客观恒定的神经机制。当我们在一个物体上扫描手指时，来自两个或更多个手指的主要信息会随着手指的张开而变化，但感知不会受到影响。与目标3相关的实验集中在汇聚机制(本体感觉和皮肤信息之间)，当外展变化时，必须操作以补偿手指位置。

The perception of 3D form depends on hand conformation and the integration of stimuli of stimuli from the multiple points of contact with the hand. To understand the neural mechanisms underlying stereognosis we need to understand three things: 1) how neurons respond to surface structure at the individual points of contact, 2) how a stimuli at separate regions of skin are integrated, and 3) how this integration depends on hand conformation. The experiments proposed here are aimed at taking a first step towards understanding these three facets of 3D form perception. Aim 1 is to determine how neurons in SI and SII cortex respond to 3D surface structure contacting a single finger. This study will be limited to surface curvature and edges of the kind that occurs when a finger contacts a rigid object. 3D surface structure varies in the plane parallel to and normal to the skin surface. The experiments related to aim 1 will study neural responses to edges and corners whose orientation and curvature vary in the plane parallel to the skin surface and neural responses to surface curvature normal to the skin surface. Aim 2 is to determine how neurons in SI and SII cortex respond to stimuli presented to two fingers. Surfaces indenting tow finger tips signal different things about an object depending on the surfaces' relative motions, orientations, and curvatures. Experiments related to aim 2 will study 1) the effects of stimulus direction and velocity; b) the effects of edge orientation, and c) the effects of surface curvature and slope on adjacent fingers. Aim 3 is to determine the neural mechanisms of objective constancy in the face of varying finger position. When we scan our fingers over an object the primary information from two or more fingers varies with finger spread but the percept is unaffected. The experimented related to Aim 3 concentrate on the convergent mechanisms (between proprioceptive and cutaneous information) that must operate to compensate for finger position when abduction varies.