Spatial navigation in the Morris water maze: working and long lasting reference memories

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Cognitive Science

Background:

• The Morris water maze (MWM) is a standard behavioral paradigm for assessing spatial learning and memory in rodents.
• Understanding the developmental trajectory of spatial navigation is crucial for interpreting cognitive performance in animal models.

Purpose of the Study:

• To investigate the development of spatial navigation and memory consolidation in male Long-Evans hooded rats using the Morris water maze.
• To differentiate between working memory and long-lasting reference memory formation and recall.

Main Methods:

• Rats (70-day-old) underwent 5 days of MWM training (10 trials/day), with escape latency recorded.
• Daily probe tests were conducted before and after training blocks.
• A final probe test was administered on Day 6 to assess memory recall after varying delays.

Main Results:

• Escape latency decreased progressively over the first 3 days, plateauing by Days 4-5.
• Short-term spatial memory (working memory) was evident in immediate probe trials after initial sessions.
• Long-term reference memory, assessed by 24-hour delayed probe trials, required approximately 30 trials over three sessions for robust formation.

Conclusions:

• Escape latency alone is an insufficient measure of long-lasting spatial memory consolidation in the MWM.
• Delayed probe trials are essential for accurately evaluating the development of reference memory.
• The findings highlight the importance of considering the timing of memory assessment in MWM studies.