About the author: Shuhan He, MD, is a resident physician at Harvard Emergency Medicine at the Massachusetts General Hospital. Shuhan is also the CEO and founder of Conduct Science, a network of companies that provide a wide range of tools aiming to improve scientific research.
Answer: A Morris Water Maze is a maze primarily designed to monitor spatial awareness and learning in rodents. It consists of a small platform that is used to escape water within the maze.
The Morris Water Maze is a small maze designed for rodents. It contains a chamber that fills up with water, and a concealed platform that the rodent must attempt to find in order to escape the water. In pre-learning trials, the rodent must learn how to get to the platform. Once the trial is active, spatial learning capabilities are measured by timing how long it takes the rodent to locate the platform which is then submerged underwater.
This maze was first introduced in the 1980s by Richard Morris at the University of St Andrews in Scotland. It has been noted for its ease of use. Rodents always find being submerged in water to be a stressful stimulus, so almost always tend to look for the platform. One of the most popular ways of monitoring spatial learning involves looking at a rodent hippocampus. This is the area of the brain most associated with the memorization of routes.
The hippocampus is responsible for two phenomenon when it comes to spatial learning - self-localization and route replay. The former is all about the organism being able to establish its location depending on its surroundings, and the latter is defined by the ability to recall a previously learned route. There is a famous study which implicates the role of the hippocampus in spatial memory - London taxi drivers have far greater amounts of hippocampal gray matter than regular people.
When it comes to the Morris Water Maze, we can learn more about the hippocampus’ role in spatial learning by monitoring its activity as rodents learn to locate the hidden platform submerged underwater.
The great thing about the Morris Water Maze is its versatility. It can also be used to learn more about the neuropsychological effects of depression, anxiety and other mental disorders. Rodents subjected to this maze tend to release substantial levels of corticosterone - a stress hormone. Also, depressed rodents exhibit similar symptoms to humans, such as lethargy. A depressed rodent might take a longer time to locate the hidden platform, due to its lower motivation to escape the stressful stimulus.
The goal of any rodent research is to transfer the findings to human behaviour. One common goal is to establish potential pharmacological solutions to human issues such as cognitive decline or a poor memory. The Morris Water Maze is the vessel of choice for many researchers looking to administer drugs to rodents in order to test cognitive performance via spatial memory.
Schizophrenia is a cognitive disorder that affects up to 1% of the human population. It is characterized by delusions and a struggle to speak. Attempting to enhance cognitive performance in sufferers is of utmost importance, and targeting the NMDA receptor in the brain has often been referenced as a potential solution.
This receptor is responsible for a great deal of learning and cognitive performance, so administering drugs which work on making this area more effective has often been shown to increase cognitive ability. The majority of supporting evidence in this case, has come from manipulating rodents in this manner before testing them with the Morris Water Maze.
In its relatively short lifespan, the Morris Water Maze has educated researchers a huge amount about human behaviour. From the effect of pharmacological treatments on cognitive ability to spatial awareness, rodents can be monitored in a variety of ways.