Place cells and place navigation

Abstract

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 conf lict 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 conf lict 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.The invitation to write an inaugural article is a unique opportunity to combine a review of what has been done with a program statement describing how we want to continue our research, explaining the philosophy of our approach, and discussing its specific tools. We should like to stress from the outset that the article does not represent an individual but a research team, the ever changing composition of which is not a weakness but a source of strength. HistoryThe present Laboratory of Neurophysiology of Memory of the Institute of Physiology of the Academy of Sciences in Prague was organized in 1958 with the aim to study nonimpulse forms of neural communication. The research concentrated on the analysis of cortical spreading depression (1), which was at the time the best known example of a neurohumoral phenomenon propagating over the entire brain surface of laboratory rodents. From the very beginning this mainly electrophysiological project lead to behavioral investigations when Buresova (2) proposed to use repeated waves of spreading depression as a functional ablation procedur...

Both here and there: Simultaneous expression of autonomous spatial memories in rats

“…However, once in the second chamber, the discharge switched to the direction indicated by a similar card placed in a different reference direction. It also was shown that hippocampal ''place cells'' can both fire in cell-specific reference frame-specific locations (10,11) and can switch between reference frames when the task changes (21) within a complex task (22) and when conflicts between idiothetic and allothetic information appear (23). Despite such changes in stimulus control, these data support the idea that the hippocampus behaves as a coherently organized spatial representation because all of the cells tend to behave in the same way within a recording session.…”

“…This important issue is unresolved in part because it is not certain whether the discharge characteristics of place cells reflect the rat's spatial cognitive state, and to settle this issue, it will take studying the cellular responses during tasks in which momentary spatial cognition can be assessed (10). It already has been shown that place cell discharge is disorganized by arena rotation in the light but not in the dark (8), but this was demonstrated during random searching when the rat was not required to use any particular spatial information.…”

“…A custom personal computer-based system tracked the light-emitting diode position in the reference frame of the room every 100 ms by using an overhead television camera. The room frame position of a second LED on the outside of the arena also was tracked and was used to calculate the rat's position in the reference frame of the arena (10).…”

Dissociation of exteroceptive and idiothetic orientation cues⋮ effect on hippocampal place cells and place navigation

“…The location was considered changed if the displacement exceeded 5% of the distance from the reference location to the most distant point of the arena. The quality of the location-speci¢c ¢ring was expressed by calculating spatial coherence, concentration and dispersion (Muller & Kubie 1989;Bures et al 1997).…”

Contribution of hippocampal place cell activity to learning and formation of goal-directed navigation in rats

“…For the understanding of functions of the HF, it is important to investigate the actual role of place cells in spatial navigation (Bures et al, 1997a(Bures et al, , 1997bZinyuk et al, 2000;Lenck-Santini et al, 2001). A purpose of the present study is to elucidate relationships between activity of HF neurons and goal-directed behaviors acquired dur-ing learning of a novel place task.…”