Fri, 25 Jul 2008 15:35:25 BST CiteULike: nelmor navigation http://www.citeulike.org/user/nelmor/tag/navigation CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/nelmor/article/2744777 <i>J. Neurosci., Vol. 28, No. 18. (30 April 2008), pp. 4679-4689.</i><br /><br />The hippocampus is essential for spatial navigation, which may involve sequential learning. However, how the hippocampus encodes new sequences in familiar environments is unknown. To study the impact of novel spatial sequences on the activity of hippocampal neurons, we monitored hippocampal ensembles while rats learned to switch from two familiar trajectories to a new one in a familiar environment. Here, we show that this novel spatial experience induces two types of changes in firing rates, but not locations of hippocampal place cells. First, place-cell firing rates on the two familiar trajectories start to change before the actual behavioral switch to the new trajectory. Second, repeated exposure on the new trajectory is associated with an increased dependence of place-cell firing rates on immediate past locations. The result suggests that sequence encoding in the hippocampus may involve integration of information about the recent past into current state. 10.1523/JNEUROSCI.4597-07.2008 Firing Rate Dynamics in the Hippocampus Induced by Trajectory Learning Daoyun Ji Matthew Wilson doi:10.1523/JNEUROSCI.4597-07.2008 J. Neurosci., Vol. 28, No. 18. (30 April 2008), pp. 4679-4689. 2008-05-02T09:18:17-00:00 2008 J. Neurosci. 28 18 4679 4689 hippocampus navigation place-cell rate-remapping http://www.citeulike.org/user/nelmor/article/2616025 <i>J Neurosci, Vol. 22, No. 20. (15 October 2002), pp. 9035-9047.</i><br /><br />This study examined the performance of spatial problems by rats when purely behavioral manipulations disturb the relationship between the place cell representation and the cues used to solve the problems. Place cells were recorded while rats performed a task in which they had to locate a goal in a gray cylinder. In the "far" task, the unmarked goal was displaced by a large fixed distance from a white card on the cylinder wall. In the "near" task, the unmarked goal was directly in front of the card. Finally, in the "cue" task the goal was marked by a black disk on the cylinder floor. Relationships between visible stimuli and place cell activity were manipulated by conducting either "hidden" (with the rat in its home cage) or "visible" (with the rat in the recording apparatus) rotations of the wall card and, when present, independent rotations of the black disk. Hidden card rotations generally caused equal firing field rotations, whereas visible card rotations often did not cause fields to move. In the far task, visible card rotations were associated with a strong decrease of correct responses in the card-referred goal area. Most rats tended to search the goal in the field-referred area. In the near task, visible card rotations were associated with a moderate decrease of performance, with rats searching the goal at the wall card. Finally, field placements had no effect on performance in the cue task. Thus, visible rotations tended to disrupt the relationship between firing fields and cues in all tasks but impaired performance only in the task that required map-based navigation. These results provide strong new evidence in favor of the spatial mapping theory of hippocampal function. Relationships between place cell firing fields and navigational decisions by rats. PP Lenck-Santini RU Muller E Save B Poucet J Neurosci, Vol. 22, No. 20. (15 October 2002), pp. 9035-9047. 2008-03-31T12:22:57-00:00 2002 J Neurosci 1529-2401 22 20 9035 9047 hippocampus map navigation place-cell rats