THE NEURAL BASIS OF INTERNAL REPRESENTATION OF PLACE

本项目的目标是应用一种新的分离技术 从行为大鼠的几个单一神经元到这个问题的棘波序列 关于熟悉的地方的内部表征是如何保持的 移除它们的启动提示(即“生物体如何继续 当灯熄灭时，你知道它在哪里吗？“)。这里有两个问题。 第一个是毫无疑问地证明实验动物 (RAT)实际上确实利用内部表征来解决空间问题 有问题。第二是发现这种能力的神经基础。 这一建议是基于O‘Keefe和Nadel的假设 海马体结构起到认知映射系统的作用。除了 病变文献导致了这一概念，它的主要支持是这样一个事实 海马区的单位活动分为两个明显的类别：‘位置’细胞 其携带位置和方向信息，以及 在平移运动中开火。这两种类型的信息可能 形成认知图谱系统的要素。这一点的延伸 这里提出的理论要求a)特定的稳定的神经模式 每当动物发现自己在熟悉的地方时，就会被放出来， B)这些模式应该表现出滞后，因为特定的地点 维护它们所需的信息应该比这少得多 需要启动它们(在限制中，所有外部信息都应 可移动的，)和c)学习了这些之间的转换之间的对应 神经状态和导致它们的运动序列应该导致 系统重新激活一系列适当的此类位置的能力 仅基于相应的电机序列的特定状态 (假设某些初始状态已由外部提供的位置设置 信息)。 将应用于此问题的新记录方法基于 单元格与两个单元格之间距离的唯一比率接近的原理 隔开的电极将产生具有独特幅度比率的尖峰 相应的记录频道。有证据表明，一种方法 基于这一原则，有效地解决了长期存在的单一 海马区的单位隔离，在那里细胞密集堆积，可能 在棘波幅度上表现出相当大的内在变化。此外, 它消除了对大单元格的一些选择偏见，并允许 同步记录到的脉冲序列之间的相互作用分析 几个神经元。

The objective of this project is to apply a new technique for the isolation of spike trains from several single neurons in behaving rats to the problem of how internal representations of familiar places are maintained upon removal of their initiating cues (i.e. "how does the organism continue to know where it is when the lights go out?"). There are two problems here. The first is to demonstrate beyond question that experimental animals (rats) actually do make use of internal representations to solve spatial problems. The second is to discover the neural basis of this ability. This proposal is based upon O'Keefe's and Nadel's hypothesis that the hippocampal formation acts as a cognitive mapping system. Apart from the lesion literature leading to this notion, its main support is the fact that hippocampal unit activity separates into two clear classes: 'place' cells which carry position and direction information, and 'theta' cells which fire during translational movements. These two types of information could form the elements of a cognitive mapping system. The extension of this theory presented here requires that a) specific stable patterns of neural discharge be set up whenever the animal finds itself in a familiar place, b) these patterns should exhibit hysteresis in that the place specific information required to maintain them should be much less than that required to initiate them (in the limit, all external information should be removable,) and c) learned correspondences between transitions among these neural states and the motor sequences leading to them should result in the ability of the system to reactivate an appropriate series of such place specific states on the basis of the corresponding motor sequences alone (given that some initial state has been set up by externally provided place information). The new recording method to be applied to this problem is based on the principle that cells which are a unique ratio of distances from two closely spaced electrodes will generate spikes with unique ratio of amplitudes on the corresponding recording channels. Evidence is presented that a method based on this principle effectively solves the perennial problems of single unit isolation in the hippocampus where cells are densely packed and may exhibit considerable intrinsic variation in spike amplitude. In addition, it removes some of the selection bias towards large cells, and permits analysis of interactions among spike trains recorded simultaneously from several neurons.