A novel control condition for spatial learning in the Morris water maze

Abstract

Background: Assessing markers of neural activity in rodent behavioural tasks benefits from meaningful comparison with matched control conditions. The Morris water maze is a widely used learning and memory task, but currently implemented control conditions are not optimal.

New method: We created a novel control condition involving random escape platform placement for each trial, while increasing the frequency of platforms throughout the training period. These control rats could therefore escape the maze by swimming in a random fashion and were not required to learn a platform location. Crucially, because the number of available escape platforms increased throughout training, their escape latencies should decline in line with rats who were learning a fixed platform location.

Results: No evidence of place learning was observed in this novel condition, but their swimming behaviour, including escape latency, distance and velocity were well matched to spatially-trained rats throughout training. Further, they did not display stress-related behaviour.

Comparison with existing methods: We contrasted this new control condition against a frequently used control where animals swim freely in the maze and showed behaviour was more closely matched to spatially-trained animals.

Conclusions: This novel control condition represents a significant advance from those currently available and may assist in the interpretation of task-related neural activity.

Keywords: Control condition; Morris water maze; Spatial learning.