The Morris Water Maze is a powerful and widely-used tool in behavioral neuroscience, designed to assess spatial learning and memory in rodents. This comprehensive guide unveils the essential components and methodology required to effectively utilize this maze for insightful research outcomes.
The Morris Water Maze comprises several crucial components:
- Circular Pool: The maze features a circular pool, often several feet in diameter, filled with water. The water is typically made opaque using a non-toxic substance, like milk, to prevent the rodents from seeing through it.
- Platform: Within the pool, a hidden escape platform is strategically positioned just below the water’s surface. The platform provides a safe refuge for the rodents during spatial learning trials.
- Visual Cues: Distinct visual cues, such as colored shapes or images, are placed around the room’s walls. These cues serve as spatial reference points for the rodents to navigate and locate the hidden platform.
- Start Locations: Different starting points around the pool’s perimeter are used for each trial to ensure varied navigation experiences for the rodents.
Preparing the Morris Water Maze
Before commencing experiments, ensure the Morris Water Maze is properly set up and maintained. The water temperature should be consistent, and the pool’s water should be made opaque. Place the maze in a controlled environment with minimal external disturbances, ensuring the visual cues are visible.
The Morris Water Maze is a widely used apparatus for assessing spatial learning and memory in rodents. Here are the dimensions of the Morris Water Maze and the materials needed to complete the assay:
Dimensions of the Morris Water Maze:
- Circular Pool: The central feature of the Morris Water Maze is a circular pool, typically constructed from plastic or fiberglass. The diameter of the pool typically ranges from 120 to 180 centimeters (approximately 47 to 71 inches). The larger the pool, the more challenging the task becomes for the rodents.
- Depth of Water: The pool is filled with water to a depth that allows the rodents to swim comfortably. The water depth is usually around 30 to 60 centimeters (approximately 12 to 24 inches). The water is often made opaque by adding a non-toxic substance such as powdered milk, ensuring that the rodents cannot see the hidden platform beneath.
- Hidden Platform: Within the pool, a submerged escape platform is strategically placed just below the water’s surface. The platform is typically circular and made from materials like acrylic or plastic. The platform’s diameter is usually around 10 to 15 centimeters (approximately 4 to 6 inches).
- Visual Cues: Visual cues are positioned around the walls of the testing room, just above the water’s surface. These cues serve as spatial reference points for the rodents to navigate and locate the hidden platform. They can take the form of colored shapes, images, or patterns.
Materials Needed to Complete the Morris Water Maze Assay:
- Morris Water Maze: Acquire a Morris Water Maze constructed from durable materials like plastic or fiberglass. Ensure that the pool’s dimensions conform to standard specifications for reliable results.
- Escape Platform: Prepare a submerged escape platform that is just below the water’s surface. The platform should be stable and allow rodents to climb onto it easily.
- Visual Cues: Set up visual cues around the walls of the testing room, ensuring they are visible to the rodents from within the pool. These cues provide spatial reference points for navigation.
- Water: Fill the pool with water to the appropriate depth, usually between 30 to 60 centimeters. Make the water opaque by adding a non-toxic substance like powdered milk to prevent the rodents from seeing the platform beneath.
- Starting Points: Designate multiple starting points around the pool’s perimeter to provide varied navigation experiences for the rodents in different trials.
- Cleaning Supplies: Have cleaning supplies on hand to maintain the cleanliness of the pool between trials, ensuring the removal of any residual odors that could affect rodent behavior.
- (Optional) Video Cameras: Install video cameras above the pool to record the rodents’ swimming behavior. Multiple camera angles may be needed to capture comprehensive data.
- (Optional) Video Recording Equipment: Set up video recording equipment, including cameras, lighting, and a recording system, to capture and store behavioral data during the experiments.
- (Optional) Control Software: Utilize appropriate control software to manage the experiment, including tracking the rodents’ paths, controlling the escape platform, and recording data.
- (Optional) Data Analysis Software: After the experiment, use data analysis software to analyze the collected behavioral data, such as latency, path length, and time spent in target quadrants.
By using these materials and adhering to proper setup procedures, researchers can conduct Morris Water Maze experiments to investigate spatial learning and memory in rodents effectively. Researchers can adapt specific details based on their experimental requirements and objectives.
Morris Water Maze Protocol
The protocol spans several days, each designated for specific training phases. It begins with acclimation to the experimental setup, followed by visible platform training to familiarize the animals with the task. The subsequent hidden platform training phase assesses the development of spatial memory. Probe trials and spatial reversal training sessions provide additional insights into memory retention and flexibility.
Acclimation (Day 0):
- Allow subjects to acclimate to the testing room for at least 30 minutes.
- Handle and habituate animals to the experimenter and the maze environment without introducing them to the water maze.
- Familiarize animals with the water maze without the platform for 2-3 trials each day.
- Monitor swimming ability, stress levels, and health status of the animals.
Training Phase (Day 2-14):
- Conduct daily training trials, 2-4 trials per day (varies and depends on your lab)
- Randomize start locations for each trial.
- Allow a maximum trial duration of 60 seconds.
- If the subject fails to locate the platform, gently guide it to the platform.
- Record latency to find the platform and the swim path for each trial.
Midpoint Probe Trial (Day 7):
- Conduct a probe trial without the platform to assess spatial memory.
- Record time spent in the target quadrant where the platform was located.
- Analyze the number of platform crossings and time spent in non-target quadrants.
Continued Training (Day 8-14):
- Continue daily training trials, maintaining the same parameters.
- Monitor for signs of fatigue or stress in subjects.
Final Probe Trial:
- Conduct a probe trial without the platform to assess spatial memory after extended training.
- Record and analyze performance metrics as in the midpoint probe trial.
- Utilize video tracking software to analyze swim paths, latency, and other relevant parameters.
- Extract data for each trial, including distance traveled, swim speed, and time to find the platform.
Cleaning and Debriefing:
- Thoroughly clean the water maze after the final data collection to eliminate olfactory cues.
- Inspect and clean the platform to remove any potential debris.
Note: Adjust the timeline and procedures based on the specific requirements of your study, the characteristics of the experimental subjects, and any unforeseen circumstances that may arise during the experiment.
Post-experiment, analyze the collected behavioral data to evaluate the rodent’s performance in terms of spatial learning and memory. Interpret the results within the context of your research objectives to gain insights into various aspects of rodent cognition.
The Morris Water Maze assay allows researchers to measure various behavioral parameters in rodents, each providing valuable insights into spatial learning and memory. Here are key behavioral parameters that can be assessed using this assay and their purpose:
|Spatial Learning & Memory
|Time taken by the animal to locate and climb onto the hidden platform
|Speed of spatial learning and memory consolidation
|Time in Target Quadrant
|The amount of time the animal spends in the quadrant where the hidden platform was located during probe trials.
|Measures spatial memory retention and the ability to associate the target location.
|Swimming Time Percentage in Quadrant
|The proportion of the total swimming time spent in the target quadrant during probe trials.
|Offers a normalized measure of spatial preference, accounting for variations in trial duration.
|The number of times the animal crosses the location where the platform was during probe trials.
|Reflects the precision of spatial memory and the ability to navigate directly to the target.
|Dwell Time in Quadrants
|Duration spent in each quadrant during probe trials
|Provides additional information on spatial preference and memory consolidation.
|Learning Index (Gallagher’s Proximity)
|A measure of how close the animal’s swim path is to the hidden platform during training trials.
|Quantifies the improvement in spatial learning over successive trials.
|0 to 1
|Cumulative Search Error
|The cumulative sum of errors in the animal’s path relative to the optimal route to the platform.
|Offers a comprehensive measure of spatial memory accuracy throughout the testing period.
|An index assessing the rate of learning by combining latency and path efficiency.
|Provides a composite measure of how efficiently the animal acquires spatial information.
|Measures the retention of spatial memory by comparing performance in initial and subsequent probe trials.
|Quantifies the degree of memory savings or deterioration over time.
|Percentage (-100% to 100%)
|Movement & Navigation Efficiency
|Swim Path Length
|The total distance traveled by the animal during a trial
|Indicates the exploration strategy and overall movement efficiency of the subject
|The velocity of the animal’s movement in the water.
|Assesses the overall swimming ability and potential impact on task performance.
|The ratio of the direct distance to the platform to the actual distance traveled by the animal.
|Evaluates the efficiency of the subject’s navigation strategy.
|Ratio; 0 to 1
|The degree of deviation from the optimal path to the hidden platform.
|Identifies errors in spatial memory and the refinement of navigation strategies.
|Time to First Platform Zone Entry
|The time taken for the animal to enter the area around the hidden platform.
|Reflects the speed of initial spatial orientation and memory retrieval.
|An error measure based on the distance between the animal’s final position and the platform location.
|Evaluates the accuracy of the animal’s final approach to the hidden platform.
|Heading Angle Error
|Measures the deviation of the animal’s heading angle from the optimal direction to the platform.
|Provides insights into the precision of the animal’s navigation strategy.
|Degrees; 0 to 360º
|Behavioral States & Strategies
|The tendency of the animal to swim along the periphery (edge) of the maze.
|Indicates anxiety levels or a lack of spatial learning, as animals may resort to less efficient strategies.
|The time the animal spends floating or immobile in the water
|Provides insights into stress levels, fatigue, or behavioral changes during the task
|Classifications of the behavioral strategies employed by the animal during maze navigation
|Describes the variety of approaches used by subjects and aids in understanding individual differences in spatial learning.
|Direct, scanning, random
Data Implications for Morris Water Maze
Implications of these results can vary depending on the research objectives:
- Cognitive Function: The Morris Water Maze is often used to study cognitive function and memory in rodents. Improved performance on latency, path length, and time in the target quadrant suggests enhanced spatial learning and memory.
- Neurological Disorders: Researchers use this assay to investigate the effects of neurological disorders or brain injuries on spatial cognition. Impaired performance may indicate cognitive deficits associated with these conditions.
- Pharmacological Interventions: The maze is valuable for testing the effects of drugs or treatments on cognitive function. Positive outcomes may suggest the potential of a drug for improving memory and learning.
- Genetic Manipulations: Researchers can assess the impact of genetic alterations on spatial learning and memory. Altered performance may reveal the role of specific genes in cognition.
- Neuroanatomy and Neurochemistry: The maze can help elucidate the involvement of brain regions and neurotransmitters in spatial learning and memory, offering insights into the neural mechanisms underlying cognitive processes.
- Augusto Foà, Francesca Basaglia, Giulia Beltrami, Margherita Carnacina, Elisa Moretto, Cristiano Bertolucci. Orientation of lizards in a Morris water-maze: roles of the sun compass and the parietal eye. Journal of Experimental Biology 2009 212: 2918-2924; doi: 10.1242/jeb.032987.
- Phillips, J. B., Youmans, P. W., Muheim, R., Sloan, K. A., Landler, L., Painter, M. S., & Anderson, C. R. (2013). Rapid learning of magnetic compass direction by C57BL/6 mice in a 4-armed ‘plus’ water maze. PloS one, 8(8), e73112. doi:10.1371/journal.pone.0073112