Brown Institute for Brain Science

Morris Water Maze

  1. Morris

Rationale of Test

This task takes advantage of the natural swimming ability of mice and their motivation to escape from the water. Spatial orienting cues are placed around the arena and mice learn the location of an escape platform based upon those cues. This task is one of the most commonly employed tasks to assess hippocampus-dependent spatial memory.

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Apparatus

The apparatus is a large circular arena (DIMENSIONS) filled 2/3 full with water. Water can be colored with a non-toxic water-soluble children’s finger paint to maximize the contrast between the mouse and the liquid. There are 4 potential locations to mount an escape platform that can either protrude just above the water or immediately below the surface of the water. Mounted above the arena is a digital camera connected to a computer with a digitizer board and video tracking software.

Procedure

The mouse is put in a pool of water and swims until an escape platform (hidden just under the surface of the water) is found. If the platform is kept in the same position and each trial begins from a different position the mouse quickly learns to use distal cues to locate the position of the platform. On the last day the mouse is tested with a probe trial, i.e., no platform is present. A subject that has learned the task well will stay more often in the target quadrant and in close proximity to the expected target location. Digital tracking software is used to collect and analyze the data from the experiment. The dependent variables include the latency to reach the escape platform and the length of the path taken to get from the start point to the target. The percent of time exploring the target quadrant during the probe trial is also used.

Interpretation

Longer latency to reach the platform, longer path to the platform, a failure to decrease the latency or path to platform across trials, and failure to preferentially swim in the target quadrat during the probe trial are used as indicators of impaired hippocampus dependent memory function.

Relevant Controls

Care should be taken to insure no impairments in swimming behavior as well as no problems in sensory function (visual function).

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