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The Effects of Dull and Enriched Environments on the Time to Run a Maze Using Laboratory Mice (Mus musculus)

Ashley Graves, Laura Nelson and Patricia Bianchino

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ABSTRACT

                Past studies have demonstrated that mice raised in enriched environments have a positive effect on the ability of individuals to complete a maze.  Whereas mice raised in dull environments tend to be inferior to mice reared in an enriched environment.  This is because enriched environments provide more stimuli which enhances the brain and can result in decreased brain weight (Neisser 1997).  The hypothesis was that mice in the enriched environment would run the maze and find the reward more quickly than those from the dull environment.  It was also hypothesized that after running the maze the first time the enriched mice would improve upon their maze time where the dull mice would take the same amount of time.  Twelve related mice were split evenly into a dull or enriched environment for a duration of ten days before running a complex maze.  Mice were returned to their appropriate environments for another ten dys before running a simple maze.  Due to the inconclusive results from the complex maze a shorter amze was prepared.  Regardless of maze size enriched mice did not run the maze at a significantly faster pace.  Future studies would include raising the mice from birth in each environment to determine if early exposure would have a greater effect on their performance. 

 

 

INTRODUCTION

                Studies show that learning ability is affected not only by genetics but by the quality of their environment.  The purpose of the experiment was to determine whether or not enriched and impoverished or dull environments made a difference in the ability of mice to complete a maze in order to receive a reward.  There is emphasis around the relationship between an organism’s infant environment and their learning ability as an adult.  The stimulation is most effective if it happens during the infancy of the organism.  It is thought that animals raised in an enriched or stimulating environment have superior learning abilities as adults in comparison to those raised in restricted or un-stimulating environments (Cooper and Zubek 1958).  In studies carried out on rats they showed an increase in brain weight when they are in an enriched environment (Neisser 1997). 

Learning is due to experience and under conditions which limit the experience an organism has they never fully use the capacity of their learning and typically perform below where they would if allowed to have experiences (Cooper and Zubek 1958).  There is a lot of evidence which shows that enriched and impoverished environments are important in developing a variety of behaviors (Henderson 1970).  There are many experiments which have been conducted on this topic and evidence that the mice or rats from enriched environments had an improved ability to run a maze (Bovet et al. 1969). 

From this evidence we decided to test this theory and had mice in different environments and then ran them through a maze.  Our hypothesis was that the mice in the enriched environment would run the maze and find the reward more quickly than those from the dull environment.  We also hypothesized that after running the maze the first time the enriched mice would improve upon their maze time where the dull mice would take the same amount of time. 


METHODS

An enriched and dull environment was set up where mice were placed for the duration of the experiment.  Both environments were a 10-gallon glass tank with bedding, a water bottle, and food.  The dull environment only contained the above conditions that were suitable to sustain life.  The enriched environment in addition had an exercise wheel and two tunnels for the mice to run through.  Both environments had six mice that came from the same litter.  Gender was not a necessary control for this experiment therefore sex was not determined. The mice were left in their assigned environment for a period of 10 days with daily basic care and minimal handling.

At the end of the first 10 day period the mice were put in a simple maze and tested to see how fast it took them to get through it.  Each mouse was placed in the maze individually and exposed to a treat, in which they would be rewarded with at the completion of the maze.  The mice were allowed to become acquainted with the reward for 30 seconds before exposed to the maze.  The maze was run two times per mouse to determine if there was a significant difference in how fast the mice learned the maze or associated the completion of the maze with a reward, depending on which environment they were raised in.

The mice were placed back into their appropriate environments for seven more days and then a second trial run was conducted.  During this trial the maze was significantly shortened to about 1/3 of the size it was when the mice first ran through it.  The same technique of exposing each mouse to the reward prior to them running the maze was used.  As before each mouse ran the maze two times to determine if a simpler maze effected whether the enriched or dull mice ran it faster.


RESULTS

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  Figure 1. The time in seconds it took each of the dull and enriched mice to complete the simple maze.  The study was to determine if the environment of the enriched mice would have an effect on abilities to run a maze, and do so faster than mice in a dull environment.

 

 

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Figure 2.  The time in minutes it took each of the dull and enriched mice to complete the complex maze.  The study was to determine if the environment of the enriched mice would have an effect on abilities to run a maze, and do so faster than mice in a dull environment. 

 

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Figure 3.  The average time in seconds it took each group of mice to complete the simple maze, where the first data point for each color is Trial 1 and the second data point of each color is Trial 2. 

 

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Figure 4.  The average time in minutes it took each group of mice to complete the complex maze, where the first data point of each color is Trial 1 and the second data point for each color is Trial 2. 

 

 

DISCUSSION

    The data that was collected from the mice were not significant.  This can be seen in Figures 3 and 4, where the R-squared values were 0.0037 and 0.0213 respectively.  Figures 1 and 2 show the individual times per mouse in each environment, and the data points were completely scattered throughout with no consistency.  There was also no difference in the length of time it took for each mouse to run the race a second time, but rather the second trial tended to take longer than the first.  This occurred for both the complex and simple maze, as seen in Figures 1 and 2.  In many cases the dull mice would often perform better in the maze than enriched mice, and found the reward in less time.  The hypothesis that the enriched mice would complete the maze at a faster rate, in conjunction to improving upon their second run of the maze was not supported by our study.  For future studies to improve upon this experiment mice should be raised from birth in their assigned environment.