Figure 1.

Age-related impairment in hippocampal-dependent place recognition memory (PRM) in older rats is rescued by exercise. Young (n = 10) and aged (n = 10) animals were assessed on the object recognition memory (ORM) (A, B) and PRM (C, D) behavioral paradigms. These involved exposing the rat to two identical objects (A1, A2) and then either replacing one of them with a new object (B in A and B) or to moving one of the original objects to a new location (B in C and D). Exploration Ratio (chance performance indicative of recognition memory failure = .5) was computed as the amount of time spent exploring the novel object or place over the entire time spent exploring. Compared with young rats, aged rats were impaired in PRM but not ORM. (E) Behavioral timeline of exercise experiment. Animals were initially tested on a battery of behavioral tests before being allocated to running or standard housing conditions. Animals remained in these conditions for the remaining duration of the study. First follow-up (FU) testing occurred at 6 weeks post running/standard housing, and second FU testing started 2 weeks later. (F) Voluntary running increased PRM performance in aged rats from impaired levels to that of young animals. There was no effect of running on ORM in older rats or on either object or PRM in young rats. Error bars in all bar graphs depict SEM. LCT, localized cue task; MWM, Morris water maze.