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|Title:||PERFORMANCE OF C57BL/6J MICE TRAINED WITH A STABLE OR RANDOMLY LOCATED ESCAPE HOLE ON THREE DIFFERENT VERSIONS OF THE BARNES MAZE.|
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|Authors/Affiliations:||1 Timothy O'Leary*, 1 Richard Brown;|
1 Dalhousie University, Halifax, NS, Canada
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|Content:||Objectives: The Barnes maze is a visuo-spatial learning and memory test originally designed for rats, and consists of a circular arena with holes around the edge. Rats use extra-maze visual cues to locate a hole which allows them to escape from bright light into a dark escape box. For testing mice, the Barnes maze has been modified in many ways, such as reducing the maze diameter and adding a wall with intra-maze visual cues around the edge. Differences in apparatus design can influence the performance of mice on the Barnes maze (O’Leary and Brown, 2007, abstract 638.16, SFN). This experiment investigated whether apparatus design also influences the visual spatial nature of the Barnes maze.|
Materials and methods: Male (N=36) and female C57BL/6J (N=36) mice were trained either with the escape hole located in a single location or with the escape hole located randomly across 16 different locations on three different Barnes maze designs; (1) a rat-sized design (122 cm), (2) a small design (69 cm) and (3) the Pompl maze design (69 cm, wall and intra-maze cues) (Pompl, et al. 1999 J. Neurosci. Meth., 87: 87-95). If mice use extra-maze visual cues to locate the escape hole, than mice trained with a stable escape hole should perform better than mice trained with a random escape hole. Mice completed 15 days of acquisition training and a probe trial to assess memory for the location of the escape hole. Reversal training was completed for 5 days with the escape hole located on the opposite side of the maze. Lastly an odor cue probe trial was completed to determine whether mice use extra-maze visual cues or intra-maze odor cues from the escape box to locate the escape hole.
Results: Although mice trained with a stable escape hole made fewer errors than mice trained with a random escape hole on all three mazes, only mice on the large maze located the escape hole faster when trained with a stable escape hole. Mice trained with a stable escape hole on the large and small mazes spent more time near the escape hole during probe trials than mice on the Pompl maze. Mice on the large maze showed larger reversal effects than mice on the small and Pompl mazes. Lastly, the odor cue probe trial showed that mice on the large maze used visuo-spatial cues to locate the escape hole, whereas mice on the small maze used both visuo-spatial and odor cues. Mice on the Pompl maze primarily used intra-maze odor cues associated with the escape box to locate the escape hole.
Conclusion: Results suggest that mice on the large maze use extra-maze visual cues to locate the escape hole, and that this is the optimal Barnes maze design for mice. On the Pompl maze, mice do not appear to use extra-maze visual cues to locate the escape hole and may rely on intra-maze odor cues.
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