Prefrontal network dynamics and top-down control of spatial representation

摘要 人类大脑灵活地处理感官输入，以提取最有用的信息并生成 最有利的反应，目前的行为策略和目标。计算灵活性， 类型通常被称为执行控制，特别是当它涉及到大脑选择实现一个 在给定的环境中，为了确定最佳的行动方针，对另一个认知过程进行比较。我们有 有限的理解如何执行控制，因此，是由生理事件介导的皮层 神经元为了增加我们对执行控制的细胞基础的了解，我建议同时 记录前额叶皮层（46区）中20-30个单独分离的神经元的集合的电活动 而在猴子执行一项要求他们发挥执行力的任务时， 控制空间认知。具体来说，猴子会将视觉刺激分配给替代空间类别 根据我们指导的可变分组标准（规则），并在逐个试验的基础上进行更改。在这 任务，我们提出了一条线，作为类别的边界，并定义空间类别的空间组 与线具有相同空间关系的位置-例如， 线包含一个类别，所有指向右边的都是另一个。通过移动和旋转边界，我们 需要大脑灵活地将一组固定的空间位置重新分配给规则中的替代空间类别- 依赖的方式，这需要大脑对空间分类施加执行控制， 认知和生理过程。我们的目标是发现执行控制如何对空间 分类是在细胞水平上实现的，通过测量分布式神经网络中依赖于规则的变化， 在给定的规则下，大脑将刺激分配给空间类别的表征。我们将 测试假设，即类别表征中规则依赖的变化将首先出现，并且是最强的 大脑前额叶皮层这将支持我们的假设，即前额叶皮层位于顶叶皮层之上， 在分布式皮质系统中，区域的层次结构介导了对认知处理的执行控制，以及 提供了一些关于神经机制的第一个细节，通过这些机制，这种控制在细胞中实现。 水平

Abstract The human brain processes sensory input flexibly to extract the most useful information and generate the most advantageous response given current behavioral strategies and goals. Computational flexibility of this type is often referred to as executive control, particularly when it involves the brain selecting to implement one cognitive process over another in order to determine the best course of action within a given context. We have a limited understanding of how executive control, as such, is mediated by physiological events in cortical neurons. To increase our knowledge of the cellular basis of executive control, I propose to simultaneously record the electrical activity of ensembles of 20-30 individually isolated neurons in prefrontal cortex (area 46) and in posterior parietal cortex (area 7a) of monkeys as they perform a task requiring them to exert executive control over spatial cognition. Specifically, monkeys will assign visual stimuli to alternative spatial categories according to a variable grouping criterion (rule) that we instruct and change on a trial-by-trial basis. In this task, we present a line that serves as a category boundary, and define spatial categories as groups of spatial positions that bear the same spatial relationship to the line - such that, for example, all points to the left of the line comprise one category, and all points to the right another. By shifting and rotating the boundary, we require the brain to flexibly reassign a fixed set of spatial positions to alternative spatial categories in a rule- dependent manner, and this requires the brain to exert executive control over spatial categorization as a cognitive and physiological process. Our objective is to discover how executive control over spatial categorization is implemented at a cellular level, by measuring rule-dependent changes in distributed neural representations of the spatial category to which the brain has assigned a stimulus under a given rule. We will test the hypothesis that rule-dependent changes in category representation will emerge first and be strongest in prefrontal cortex. This will support our hypothesis that prefrontal cortex sits above parietal cortex in a hierarchy of areas mediating executive control over cognitive processing in distributed cortical systems, and provide some of the first detail about the neural mechanisms by which this control is implemented at a cellular level.