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Maze Overview
The basic procedure for the Morris Water Maze is the rat is placed in the water maze, a large circular pool, and is ultimately supposed to find the invisible platform that will allow it to escape the water. The experimenters can manipulate multitudes of variables placed upon them, including gender, the environment, exposure to drugs, etc. These factors may affect spatial movement and memory. There are three basic tactics for the rats to escape the maze: a praxic strategy (remembering the movements needed to get to the platform), a taxic strategy (the rat uses visual cues to reach their destinations), or spatial strategy (using distal cues as points of reference to locate themselves). It is now a standard test for determining changes in memory and learning in mice and identifying how neural systems correlate to these behavioral changes.

Original Experiment
For Richard G. Morris' first Maze navigation experiment, the apparatus was a large circular pool with the dimensions of 1.30 m across and .060 m high, and the original subject of the experiment was rats. The experiment is now mainly used on mice. The purpose of the original experiment was to show that spatial learning does not require the presence of local cues, meaning that rats can learn to locate an object without any auditory, visual, or olfactory cues. While the original idea of the maze has remained, the task has been expanded to assess drug and alcohol administration, socialization effects, age differences, etc.

Discoveries in Neuroscience
Many variables can have an imperative effect on how mice and rats perform in the task, but two major factors that experimenters investigate are the effects of mice and rats environments on their performance, as well as the effect of drug use.

Pharmacological Manipulation
The Morris Water Maze is used effectively to determine the short and long term effects of drugs on the brain. For example, after giving rats daily injections of cocaine, for as long as three months after the fact the rats had a harder time locating the platform, showing that the exposure of cocaine impaired the rats ability to perform for up to three months.

Environmental Effects
In a different experiment, based on socialization factors rather than pharmacological, two groups of rats were used. One group was raised in isolation while the other was raised socially, and the group raised in isolation performed better in the navigation task. The conclusion taken from this experiment was that the rats environment had the ability to change their neurotransmissions in the cholinergic system. Age difference between groups of rats is a way to gauge hippocampal-based spatial memory, which can be the most prone to degeneration because of aging.

Gender is also a main variable that can differentiate results and shows how male and female rats learn differently. Male and female rats solve the task using different kinds of spatial cues. This theory is shown in an experiment that utilized different spatial cues to measure differences. In the trial where the release location remained constant, there were no differences in regards to gender. When the release location changed between two trials, females showed less memory of where the platform was located. However, during a third trial where the release position changed but distant visual cues remained constant, females were as proficient at males at the task.

Criticisms
When the searching times for the platform in the target quadrant are reduced in the probe trial, it is used as direct evidence that the spatial memory of the mouse must be impaired. However, many times the reason for a lengthier amount of time spent looking for the platform, or the lack of searching in the target quadrant, has nothing to do with an effect on the mouse’s spatial memory, but is actually due to anxiety or lack of orientation. Based off of an experiment that researched the reasons behind variability in behavior scores, factor one was “thigmotaxis”, which equates to swimming along the wall finding the platform by touch. The second factor was passivity. The third factor was memory. Of these three main factors, only one was cognitive, memory, and was the reason for differing search times only 13% of the time.