Figure 3.

Results of mnemonic similarity task pre-training and tests in Experiment 2. (A) Cumulative frequency plot showing the percentage of young (n = 10) and aged (n = 10) rats that achieved criterion of ≥81.3% correct responses across pre-training sessions with the target object and a distinct object. (B) Mean (±SEM) percent correct responses for each trial type presented on mnemonic similarity tests. Values are collapsed across four tests given over a period of 12 days, to a total of 40 trials with each lure object (distinct ‘Frog’ object, Lure objects 1–3, or an identical pair of copies of the target object). Both age groups showed poor performance on the high-similarity discriminations between the target and Lure 3 (L3), relative to lower-similarity discriminations with Lure 1 (L1) or Lure 2 (L2) (main effect of similarity: p < 0.001). Relative to young, aged rats showed impaired performance on Lure 2 and Lure 3 trials (p < 0.001). (C) Mean (±SEM) percent correct responses for each trial type plotted for each of the four test sessions. Performance did not improve significantly in young or aged rats across test days, for any trial type (p’s > 0.16). However, aged rats showed performance deficits on Lure 2 and Lure 3 trials across test days (p’s < 0.001). *** p < 0.001.