Figure 2.

Multistability of place representation in old rats. Parallel recordings of single units in hippocampal area CA1 made on two consecutive experiences of a “Figure 8” maze (Maze 1, Maze 2; see figure 8 of ref. 18) for one old and one young rat. Between each recording session, the rats were removed from the room. Each color represents the spikes of a single unit recorded as the rat traversed the maze. The rat's movements through the maze are represented by the underlying gray traces. For the young rat, the spatial representation is highly consistent between visits. In contrast, the older rat exhibits an almost complete redistribution of the firing fields between the two visits. [Reproduced with permission from Barnes et al. (1997) Nature (London) 388, 272–275 (Copyright 1997, Macmillan Magazines Ltd).]