Visual/Spatial Properties of Posterior Parietal Neurons

描述(申请人提供)：本申请是为了研究大脑皮层感觉-运动转换是如何完成的。特别是，我们将研究如何在皮质中表示空间信息(目标1)，以及如何在这些表示之间完成坐标转换(目标2)。以前关于这些主题的工作已经研究了如何表示空间来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，通常包括手眼运动和双手运动。在目标1中，我们将提出一项新的发现，在上一次授予期间，在背侧运动前皮质(PMD)，手、眼睛和REACH的目标的相对编码。这一目标将测试相对编码的几个新方面和含义。(1)它将检查感觉运动通路的其他区域，包括第5区和初级运动皮质的相对编码范围。(2)它将确定这两个肢体是否也在涉及伸展的皮质区域显示出相对编码。这一结果将表明，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，并根据任务的不同而变化，或者它是否是“硬连线”的。(4)它将确定眼动区域是否也显示了眼动任务中眼睛和手的相对编码，这有助于眼手协调。(5)它将直接测试这样一个假设，即相对编码本质上是工作空间中的平移(也许还有旋转)不变性。在目标2中，我们将研究增益场机制，它被认为负责表示之间的坐标转换。(1)该目标将确定增益场是否与相对位置编码同时存在。(2)它将决定大脑皮质特定区域的增益场是与身体周围的外部空间有关，还是与身体内部的内部空间有关。3)将确定增益调制的数学机制。我们将区分它是输入的纯乘法还是近似乘法的函数，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具有广泛的适用性，以理解超越坐标变换的神经处理。拟议的研究结果可用于帮助因中风和创伤性脑损伤而遭受额叶和顶叶皮质损伤的患者设计治疗方案。它们将有助于了解影响皮质功能的神经系统疾病造成的缺陷，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.