Bures J, Fenton A A, Kaminsky Y, Zinyuk L
Institute of Physiology, Academy of Sciences of the Czech Republic, Prague.
Proc Natl Acad Sci U S A. 1997 Jan 7;94(1):343-50. doi: 10.1073/pnas.94.1.343.
The assumption that hippocampal place cells (PCs) form the neural substrate of cognitive maps can be experimentally tested by comparing the effect of experimental interventions on PC activity and place navigation. Conditions that interfere with place navigation (darkness, cholinergic blockade) but leave PC activity unaffected obviously disrupt spatial memory at a post-PC level. Situations creating a conflict between egocentric and allocentric orientation (place navigation in the Morris water maze filled with slowly rotating water) slow down spatial learning. PC recording in rats searching food pellets in a rotating arena makes it possible to determine which firing fields are stable relative to the room (allocentrically dependent on sighted extramaze landmarks), to the surface of the arena (dependent on egocentric path integration mechanisms and intra-arena cues), or disappear during rotation. Such comparison is made possible by the computerized tracking system simultaneously displaying a rat's locomotion and the respective firing rate maps both in the room reference and arena reference frames. More severe conflict between allocentric and egocentric inputs is produced in the field clamp situation when the rat searching food in a ring-shaped arena is always returned by rotation of the arena to the same allocentric position. Ten-minute exposure to this condition caused subsequent disintegration or remapping of 70% PCs (n = 100). Simultaneous examination of PC activity and navigation is possible in the place avoidance task. A rat searching food in a stationary or rotating arena learns to avoid an allocentrically or egocentrically defined location where it receives mild electric footshock. In the place preference task the rat releases pellet delivery by entering an unmarked goal area and staying in it for a criterion time. Both tasks allow direct comparison of the spatial reference frames used by the PCs and by the behaving animal.
海马体位置细胞（PCs）构成认知地图的神经基础这一假设，可以通过比较实验干预对PC活动和位置导航的影响来进行实验验证。干扰位置导航的条件（黑暗、胆碱能阻断）但不影响PC活动，显然会在PC之后的水平上破坏空间记忆。在自我中心和空间中心定向之间产生冲突的情况（在充满缓慢旋转水的莫里斯水迷宫中进行位置导航）会减缓空间学习。在旋转竞技场中寻找食物颗粒的大鼠中进行PC记录，可以确定哪些放电场相对于房间是稳定的（空间中心依赖于可见的迷宫外部地标），相对于竞技场表面是稳定的（依赖于自我中心路径整合机制和场内线索），或者在旋转过程中消失。通过计算机化跟踪系统同时显示大鼠的运动以及在房间参考系和竞技场参考系中的相应放电率图，使得这种比较成为可能。当在环形竞技场中寻找食物的大鼠总是通过竞技场的旋转回到相同的空间中心位置时，在电场钳制情况下会产生更严重的空间中心和自我中心输入之间的冲突。暴露于这种情况十分钟会导致随后70%的PCs（n = 100）解体或重新映射。在位置回避任务中可以同时检查PC活动和导航。在固定或旋转竞技场中寻找食物的大鼠学会避免一个空间中心或自我中心定义的位置，在该位置它会受到轻微的足部电击。在位置偏好任务中，大鼠通过进入一个未标记的目标区域并在其中停留一段标准时间来释放食物颗粒。这两个任务都允许直接比较PCs和行为动物所使用的空间参考系。
