How relative stability between visual cues affects cue control of CA1 place cells

Visual cues help rats to maintain an internal representation of orientation. However, in a changing environment, it is important to choose the most informative cues to guide navigation. We hypothesise that cues are more informative when they maintain stable relative positions with other cues in the environment, as such stability allows the position of one cue to reliably predict the position of another. To test the hypothesis, we record CA1 hippocampal place cells in rats as they foraged for food pellets on a circular platform in a cue controlled environment. Four distinct visual cues were fixed onto black curtains surrounding the platform. Three of the cues were assigned as the stable cues, while one was unstable. Between sessions, conflicts were introduced by changing the positions of all four cues in a way that only the relative relationships between the three stable cues remained fixed. The rats were given four conflict experiences in one day for four days. We found that in most cases the place cells rotated their place fields coherently after the conflicts. However, rather than consistently rotating with the stable cues in different conflict sessions, they typically rotated coherently with either the stable cues, the unstable cues, the room cues or to some other locations. In a minority of sessions, they did not rotate coherently, suggesting remapping between sessions. These data do not support the hypothesis that stable cues are more likely to influence the place fields of place cells in CA1, and suggest instead that, during each session, the network is preferentially influenced by either stable, unstable, or room cues in a coherent but unpredictable fashion.