Visual/Spatial Properties of Posterior Parietal Neurons

描述（由申请人提供）：本申请旨在研究大脑皮层的感觉-运动转换是如何完成的。特别是，我们将研究空间信息是如何在皮层中表示的（目标1），以及这些表示之间的坐标转换是如何完成的（目标2）。关于这些主题的先前工作已经研究了如何表示空间以实现单个效应器的运动，例如眼睛或手。然而，运动通常涉及多个效应器，通常包括手眼和双手运动。在Aim 1中，我们将提出一个新的发现，在上一个资助期间，在背侧运动前皮层（PMd）中，手，眼睛和到达目标的位置的相对编码。这个目标将测试相对编码的几个新方面和含义。(1)它将检查包括5区和初级运动皮层在内的感觉运动通路的其他区域的相对编码程度。{2)判断两肢是否在涉及伸手的皮质区域也表现出相对编码。这一结果表明，相对编码可能是涉及多个身体部位的运动的一般机制。(3)它将检查手的相对编码在PMd中是否依赖于状态，并根据任务而变化，或者是否“硬连线”。(4)它将确定眼动区域是否也显示眼动任务的眼和手的相对编码，从而促进眼手协调。(5)它将直接测试相对编码的假设，就其本质而言，是跨工作空间的平移（也许是旋转）不变的。在目标2中，我们将研究增益场机制，它被认为是负责表示之间的坐标转换。(1)此目的将确定增益场是否与相对位置编码同时存在。(2)它将决定大脑皮层特定区域的增益场是与身体周围的外在空间有关，还是与身体内部的内在空间有关。3)确定增益调制的数学机制。我们将区分它是输入的纯粹乘法还是近似乘法的函数，例如非线性加法。由于增益场被认为是神经计算的一般机制，这些研究的结果应该广泛适用于理解坐标变换以外的神经处理。提出的研究结果可用于帮助设计治疗因中风和创伤性脑损伤而遭受额叶和顶叶皮层损伤的患者的疗法。它们将有助于理解由影响皮质功能的神经系统疾病引起的缺陷，并可以指导这些疾病的诊断和治疗。

DESCRIPTION (provided by applicant): This application is to study how sensory-motor transformations are accomplished in the cerebral cortex. In particular we will examine how spatial information is represented in cortex (Aim 1) and how coordinate transformations are accomplished between these representations (Aim 2). Previous work on these topics has examined how space is represented for achieving the movement of a single effector, for instance the eyes or the hand. However, movements generally involve multiple effectors and typically include hand-eye and bimanual movements. In Aim 1 we will advance a new finding, made in dorsal premotor cortex (PMd) during the last grant period, of a relative coding of the position of the hand, eyes and goal of a reach. This aim will test several new aspects and implications of relative coding. (1) It will examine the extent of relative coding in other areas of the sensorimotor pathway including area 5 and primary motor cortex. {2) It will determine if the 2 limbs also show a relative coding in cortical areas involved in reaching. Such a result would indicate that relative coding may be general mechanism for movements involving multiple body parts. (3) It will examine if relative coding of the hand is state dependent in PMd, and changes depending on the task, or if it is "hard wired". (4) It will determine if eye movement areas also show a relative coding of the eye and hand for eye movement tasks, which made facilitate eye- hand coordination. (5) It will directly test the hypothesis that relative coding, by its nature, is translation (and perhaps rotation) invariant across the workspace. In Aim 2 we will examine the gain field mechanism that is thought to be responsible for coordinate transformations between representations. (1) This aim will determine if gain fields exist simultaneously with relative position encoding. (2) It will determine whether gain fields in particular areas of cortex are concerned with extrinsic space around the body or intrinsic space within the body. 3) The mathematical mechanism for gain modulation will be determined. We will distinguish whether it is a pure multiplication of inputs or a function which approximates multiplication such as non-linear addition. Since gain fields are believed to be a general mechanism for neural computation, the results of these studies should have broad applicability to understanding neural processing beyond coordinate transformations. The results of the proposed studies can be used to help design therapies for patients suffering from damage to frontal and parietal cortex from strokes and traumatic brain injuries. They will help in understanding deficits that result from neurological diseases that effect cortical functioning, and can guide the diagnoses and treatments for these diseases.