Bures J, Fenton A A, Kaminsky Y, Rossier J, Sacchetti B, Zinyuk L
Institute of Physiology, Academy of Sciences, Prague, Czech Republic.
Philos Trans R Soc Lond B Biol Sci. 1997 Oct 29;352(1360):1515-24. doi: 10.1098/rstb.1997.0138.
Navigation by means of cognitive maps appears to require the hippocampus; hippocampal place cells (PCs) appear to store spatial memories because their discharge is confined to cell-specific places called firing fields (FFs). Experiments with rats manipulated idiothetic and landmark-related information to understand the relationship between PC activity and spatial cognition. Rotating a circular arena in the light caused a discrepancy between these cues. This discrepancy caused most FFs to disappear in both the arena and room reference frames. However, FFs persisted in the rotating arena frame when the discrepancy was reduced by darkness or by a card in the arena. The discrepancy was increased by 'field clamping' the rat in a room-defined FF location by rotations that countered its locomotion. Most FFs dissipated and reappeared an hour or more after the clamp. Place-avoidance experiments showed that navigation uses independent idiothetic and exteroceptive memories. Rats learned to avoid the unmarked footshock region within a circular arena. When acquired on the stable arena in the light, the location of the punishment was learned by using both room and idiothetic cues; extinction in the dark transferred to the following session in the light. If, however, extinction occurred during rotation, only the arena-frame avoidance was extinguished in darkness; the room-defined location was avoided when the lights were turned back on. Idiothetic memory of room-defined avoidance was not formed during rotation in light; regardless of rotation, there was no avoidance when the lights were turned off, but room-frame avoidance reappeared when the lights were turned back on. The place-preference task rewarded visits to an allocentric target location with a randomly dispersed pellet. The resulting behaviour alternated between random pellet searching and target-directed navigation, making it possible to examine PC correlates of these two classes of spatial behaviour. The independence of idiothetic and exteroceptive spatial memories and the disruption of PC firing during rotation suggest that PCs may not be necessary for spatial cognition; this idea can be tested by recordings during the place-avoidance and preference tasks.
通过认知地图进行导航似乎需要海马体；海马体位置细胞（PCs）似乎存储空间记忆，因为它们的放电局限于称为放电场（FFs）的特定细胞位置。对大鼠进行的实验操纵了自身运动和地标相关信息，以了解PC活动与空间认知之间的关系。在光照下旋转圆形竞技场会导致这些线索之间出现差异。这种差异导致竞技场和房间参考框架中的大多数FFs消失。然而，当差异因黑暗或竞技场中的一张卡片而减小时，FFs在旋转竞技场框架中持续存在。通过与大鼠运动相反的旋转将其“场钳制”在房间定义的FF位置，差异会增加。大多数FFs在钳制一小时或更长时间后消散并重新出现。位置回避实验表明，导航使用独立的自身运动和外感受记忆。大鼠学会在圆形竞技场中避开未标记的电击区域。当在光照下的稳定竞技场上习得时，通过使用房间和自身运动线索来学习惩罚的位置；在黑暗中消退会转移到下一次光照实验中。然而，如果在旋转过程中发生消退，只有竞技场框架回避在黑暗中被消除；当灯光重新亮起时，房间定义的位置仍会被避开。在光照下旋转过程中不会形成房间定义回避的自身运动记忆；无论是否旋转，关灯时都没有回避行为，但灯光重新亮起时房间框架回避会重新出现。位置偏好任务通过随机分散的颗粒奖励对以自我为中心的目标位置的访问。由此产生的行为在随机颗粒搜索和目标导向导航之间交替，使得可以检查这两类空间行为的PC相关性。自身运动和外感受空间记忆的独立性以及旋转过程中PC放电的中断表明，PCs对于空间认知可能不是必需的；这个想法可以通过在位置回避和偏好任务期间进行记录来验证。
