COMPUTATIONAL BASIS OF THE HEAD DIRECTION CELL SIGNAL

当老鼠在太空中航行时，被称为头部方向细胞的神经元 提供瞬时方向航向的持续指示。 每个小区 当动物面对一个特定的方向时就会开火。 每个细胞都有 它自己的射击方向，所以每个方向都是由活动发出信号， 这些细胞的独特子集。 目前尚不清楚这些信号是如何产生的。 令人惊讶的是，没有 地磁影响的证据 相反，细胞受到影响， 部分，通过视觉线索;突出的视觉地标可以“设置”黑暗。 因此，细胞还必须使用信号化头部角运动的线索（例如， 前庭或视觉运动线索），因为在没有界标的情况下，这些 是唯一持续的指向性指标 在几个相互连接的大脑中发现了头部方向细胞 区域，包括后下托、压后皮质、背侧 丘脑核和丘脑前核。 反过来，这些领域是 与其他几个区域相连，包括网状丘脑 核、乳头体、顶盖前区和上级丘。 细胞 在后一个区域中，尚未检查方向相关性。 这些研究的目的是检查这个电路中的每个区域， 细胞（除了头部方向细胞本身）的存在， 构成用于头部方向信号的构建块。 细胞 每个区域将记录动物在执行食物时的导航 颗粒回收任务。 动物将配备两个前灯， 其提供动物瞬时方向的连续指示 航向 每个区域的细胞活动将被检查是否有任何方向， 视觉或角运动相关。 任何这样的感觉基础 将在探测研究中检查信号，包括1）熄灯期 来测试视觉效果 2)被动旋转会话，用于测试 依赖于动物自身的运动，以及3）递送 实验者产生的前庭和视觉运动线索。 完成后，拟议的研究，沿着早期的工作，将提供 一个完整的检查基本导航相关的射击性能， 头部方向单元电路。 这将为发展提供基础 对这些细胞的理论解释 这是一个重要的目标 因为1）它将提供一个神经电路如何生成 高度抽象的表示（头部方向），2）它将提供 洞察整体认知和感知的一个方面， 导航的能力。

As a rat navigates through space, neurons known as Head Direction cells provide an ongoing indication of momentary directional heading. Each cell fires when the animal is facing one particular direction. Every cell has its own firing direction, so that each heading is signalled by activity in a unique subset of these cells. It is not clear how these signals are generated. Surprisingly, there is no evidence for geomagnetic influences. Rather, the cells are influenced, in part, by visual cues; salient visual landmarks can "set" the darkness. Thus, the cells must also use cues which signal angular head motion (e.g., vestibular or visual motion cues) since, in the absence of landmarks, these are the only ongoing indicators of directional heading. Head Direction cells have been found in several interconnected brain regions, including the postsubiculm, retrosplenial cortex, laterodorsal thalamic nucleus, and anterior thalamic nuclei. These areas, in turn, are connected to several other regions, including the reticular thalamic nucleus, mammillary bodies, pretectal area and superior colliculus. Cells in the latter areas have not yet been examined for direction correlates. The goal of these studies is to examine each area in this circuit for the presence of cells (other than Head Direction cells themselves) which could constitute the building blocks for the head direction signal. Cells in each area will be recorded as animals navigate while performing a food pellet retrieving task. The animals will be equipped with two headlights, which provide a continual indication of the animal's momentary directional heading. Cell activity in each area will be examined for any directional, visual, or angular motion correlates. The sensory basis of any such signals will be examined in probe studies including 1) lights out sessions to test for visual influences. 2) passive rotation sessions, to test for dependence on the animal's own motor movements, and 3) delivery of experimenter-generated vestibular and visual motion cues. When completed, the proposed studies, along with earlier work, will provide a complete examination of the basic navigation related firing properties in the Head Direction cell circuit. This will provide a basis for development of a theoretical explanation for these cells. This is an important goal because 1) it will provide an example of how a neural circuit can generate a highly abstract representation (head direction), and 2) it will provide insight into one aspect of the overall set of cognitive and perceptual abilities involved in navigation.