Comparison of shape coding in somatosensory and visual cortex

描述(申请人提供)：这项研究计划的目标是研究清醒恒河猴(猕猴)大脑中潜在的2D形式处理的神经机制。具体目的1是描述初级(SI)和次级(SLL)躯体感觉皮层神经元对由弧形和角度组成的一大组缩进的2D形状的反应。在目标1a中，将使用标准的神经生理学技术收集神经反应。触觉形状将使用定制的触觉刺激器呈现在动物的指垫上。答复将使用标准统计分析进行量化。关于形状处理性质的特定假设(即表示什么形状信息？)将使用相互竞争的数学模型进行测试。这些模型将测试神经元代表轮廓位置、方向和曲率的程度。目标1b的目标是了解单个神经元中的形状信号是如何产生的。为此，将使用包括时间加权参数的模型来表征形状表示的时间进程。具体目标1的最终目标是了解形状信息如何从SI转换为SLL。目标1c将结合目标1a和1b的结果来模拟SI和SLL之间的相互作用。我们的工作假设是，高级神经元(区域2/SII)整合了关于简单方位特征的信息(在区域3b/1处理)，以形成角度和曲率的显式表示。具体目的2是测试V4区的视神经元是否使用类似的编码策略来表示曲率。在这些实验中，与在特定目标1中开发的模型相同类型的模型将应用于先前从V4神经元收集的数据。这些神经元被提供了一组2D视觉刺激，类似于用于特定目标1的触觉形状。形状模型将根据视觉神经元的反应进行迭代改进。我们将测试这一假设，即V4中的神经元，据报道代表曲率，以类似于区域2和SLL中的神经元的方式处理形状；即，通过组合简单的方向特征来形成复杂轮廓几何的表示。这一提议的最终目标是了解形状信息是如何在大脑中产生和转化的。对这种转换的了解是理解神经回路如何在感觉运动功能的系统水平上工作的关键。这对未来一代截肢者和盲人神经假体的设计具有重要的指导意义。这一知识也影响了中风、糖尿病和自闭症等发育障碍引起的感觉障碍的临床治疗方法。

DESCRIPTION (provided by applicant): The goal of this research proposal is to investigate neural mechanisms underlying 2D form processing in the brain of the awake rhesus monkey (Macaca mulatta). Specific Aim 1 is to characterize the responses of neurons in primary (SI) and secondary (Sll) somatosensory cortex to a large set of indented 2D shapes comprising arcs and angles. In Aim 1 a, neural responses will be collected using standard neurophysiological techniques. Haptic shapes will be presented to the animal's finger pad using a custom-built tactile stimulator. Responses will be quantified using standard statistical analyses. Specific hypotheses regarding the nature of shape processing (i.e. what shape information is represented?) will be tested using competing mathematical models. The models will test the degree to which neurons represent contour position, orientation, and curvature. The goal of Aim 1b is to understand how the shape signal is derived in individual neurons. To this end, the time course of the shape representation will be characterized using models comprising temporally weighted parameters. A final goal of Specific Aim 1 is to understand how shape information is transformed from SI to Sll. Aim 1 c will combine the results from Aims 1 a and 1 b to model the interactions between SI and Sll. Our working hypothesis is that higher-level neurons (area 2/SII) integrate information about simple orientation features (processed in areas 3b/1) to form explicit representations of angles and curvatures. Specific Aim 2 is to test whether visual neurons in area V4 use similar coding strategies to represent curvature. In these experiments, the same types of models as those developed in Specific Aim 1 will be applied to previously collected data from V4 neurons. These neurons were presented with a set of 2D visual stimuli analogous to the haptic shapes to be used in Specific Aim 1. The shape models will be iteratively refined on the responses of the visual neurons. We will test the hypothesis that neurons in V4, which reportedly represent curvature, process shape in a manner similar to neurons in area 2 and Sll; namely, by combining simple orientation features to form representations of complex contour geometry. The ultimate goal of this proposal is to understand how shape information is generated and transformed in the brain. Knowledge of this transformation is key to understanding how neural circuits work on a systems level in sensorimotor functions. It has major implications on the design of future generations of neural prosthetics for amputees and blind subjects. This knowledge also impacts clinical approaches to sensory deficits caused by stroke, diabetes, and developmental disorders like autism.