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. 2016 Jul;23(7):339–348. doi: 10.1101/lm.042069.116

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© 2016 Johnson et al.; Published by Cold Spring Harbor Laboratory Press

This article is distributed exclusively by Cold Spring Harbor Laboratory Press for the first 12 months after the full-issue publication date (see http://learnmem.cshlp.org/site/misc/terms.xhtml). After 12 months, it is available under a Creative Commons License (Attribution-NonCommercial 4.0 International), as described at http://creativecommons.org/licenses/by-nc/4.0/.

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Figure 1. — Aged rats show impairments in spatial memory on the Morris water maze task that are not attributable to visual, motor, or motivational deficits. (A) Cumulative integrated path length (CIPL) values reflecting the total distance traveled (cm) prior to locating the hidden platform during water maze training, corrected for swim speed differences. All rats learned to locate the platform more effectively across training blocks 1–4 (main effect of block: P < 0.001), such that CIPL values for block 1 were greater than those for each other block (within subjects contrasts: Ps < 0.01). The decrease in CIPL from block 1 to block 2 likely reflects procedural learning, and did not differ based on age. However, young rats continued to refine their swim strategy from blocks 2 through 4, while aged did not (main effect of age: P < 0.05). (B) Mean proximity to the platform's target location during Probe tests 1 through 4. Proximity values decreased in both groups across probe tests (main effect of test: P < 0.0001), but were greater overall in aged rats, reflecting poor memory for the target location (main effect of age: P < 0.03). (C) Spatial learning index (SLI) values calculated for young and aged rats. Lines indicate group means. SLI values for aged rats were greater than those of young, reflecting spatial memory deficits (P < 0.008). (D) Swim path lengths (cm) of young and aged rats did not differ when the platform location was visible (P = 0.33). Graphs show mean ± SEM. (*) P < 0.05 (**) P < 0.01.