Figure 6.

Assessment of spatial learning and memory abilities on the water maze task, and relationship of spatial abilities to object discrimination training in Experiment 1. (A) Cumulative integrated path length (CIPL) values reflecting the total distance traveled (cm) prior to locating the hidden platform during spatial training, corrected for swim speed differences. All rats learned to locate the platform more effectively across training blocks (B1–B4; main effect of block: p < 0.001), but there was no difference in rate of acquisition between young and aged rats (p = 0.46). (B) Mean proximity (cm) to the platform’s target location during four probe tests of spatial reference memory (P1–P4). Proximity values decreased in both age groups across probe tests, reflecting an improvement in memory for the hidden platform’s location over time (main effect of test: p < 0.001); however, no difference was detected in spatial memory between young and aged (p = 0.27). (C) Swim path lengths (cm) of young and aged rats did not differ on cued navigation trials (p = 0.95). Graphs show means ± SEM. (D. E) Scatter plots show normalized number of incorrect responses required to learn to discriminate between the similar object pair in Experiment 1 and normalized measures of (D) spatial learning (block 3 CIPL values) and (E) spatial memory (spatial learning index; SLI). No relationship was detected between discrimination and spatial abilities in young or aged rats. (F, G) When aged rats were segregated into unimpaired (AU) and impaired (AI) groups based on similar object discrimination training required in Experiment 1, no differences between the two groups or with respect to young (Y) rats were observed in (F) block 3 CIPL values or (G) SLI values.