Morris Water Maze Probe Trial
Overview
The Morris water maze probe trial is the definitive test of spatial reference memory, conducted after the animal has learned to locate a hidden escape platform over multiple acquisition days. During the probe trial, the platform is removed from the pool, and the animal swims freely for 60 seconds. The spatial specificity of the memory is revealed by the proportion of time the animal spends searching in the target quadrant (where the platform was located) versus the three non-target quadrants, and by the number of times it crosses the exact former platform location. A well-trained animal with intact spatial memory will spend significantly more than 25% of the trial in the target quadrant and make multiple platform crossings.
Beyond quadrant time and platform crossings, modern analyses include the proximity measure (mean distance from the former platform location over the trial), initial heading error (direction of the first body length of swimming), latency to first target zone entry, and search strategy classification (spatial, systematic, or random). The proximity measure is considered the most sensitive single metric because it captures the spatial precision of the search independently of path characteristics. Search strategy analysis classifies the swim path into behavioral categories that reveal whether animals use hippocampal-dependent allocentric spatial strategies or striatal-dependent response strategies.
ConductMaze generates comprehensive probe trial analyses from continuous overhead tracking data, including heat maps of spatial occupancy, time-in-zone calculations for customizable target regions, platform crossing counts, proximity curves, and automated search strategy classification using published algorithms. The software allows experimenters to define annular, quadrant, and circular target zones and exports all metrics with associated statistical comparisons to chance performance.
Trial Flow
Platform Removal
The escape platform is removed from the pool before the probe trial begins.
Trial Initiation
Animal is placed in the pool at the start position opposite the former platform location.
Free Swimming
Animal swims freely for 60 seconds while continuous position data are recorded.
Zone Analysis
Time in each quadrant and target zone is computed from position data in real time.
Platform Crossing Detection
Each time the swim path crosses the former platform location, a crossing is counted.
Metrics Computation
All probe metrics including proximity, heading error, and search strategy are computed.
Trial End
Animal is removed after 60 seconds; heat maps and summary data are exported.
Parameters
| Parameter | Type | Default | Description |
|---|---|---|---|
| Probe Duration | duration | 60s | Duration of the probe trial during which the animal swims without a platform. |
| Start Position | enum | opposite-to-target | Release point for the probe trial, typically opposite the former platform quadrant. |
| Target Zone Radius | distance | 15cm | Radius of the circular target zone centered on the former platform location. |
| Pool Diameter | distance | 120cm | Diameter of the circular water maze pool. |
| Analysis Time Window | duration | 60s | Duration of tracking data used for analysis (can be truncated to first 30s for sensitivity). |
| Search Strategy Algorithm | enum | garthe-2009 | Algorithm used for automated search strategy classification. |
| Water Temperature | temperature | 22C | Water temperature maintained during the probe trial. |
Metrics
| Metric | Unit | Description |
|---|---|---|
| Target Quadrant Time % | % | Percentage of probe trial time spent in the quadrant that previously contained the platform. |
| Platform Crossings | count | Number of times the swim path crosses the exact former platform location. |
| Mean Proximity | cm | Average distance from the former platform location sampled at regular intervals over the trial. |
| Latency to Target Zone | s | Time from trial start to first entry into the circular target zone. |
| Initial Heading Error | degrees | Angular deviation of the first body-length of swimming from the direct path to the target. |
| Search Strategy | category | Classified swim strategy: spatial-direct, spatial-focal, systematic-scanning, or random. |
| Swim Speed | cm/s | Average swimming velocity during the probe trial. |
| Thigmotaxis % | % | Percentage of time spent in the outer annulus of the pool (wall-hugging behavior). |
Sample Data
| Subject | Group | Target Quadrant % | Platform Crossings | Mean Proximity (cm) | Heading Error (deg) |
|---|
Representative data for illustration purposes. Actual values will vary by species, strain, and experimental conditions.
Applications
- 1Spatial Reference Memory Assessment — Gold-standard evaluation of long-term allocentric spatial memory after multi-day acquisition training.
- 2Alzheimer Disease Models — Quantifying progressive spatial memory loss in APP/PS1, 3xTg-AD, and 5xFAD transgenic mice at specific ages.
- 3Pharmacological Rescue — Demonstrating that procognitive agents restore target quadrant preference and reduce proximity to chance level.
- 4Search Strategy Analysis — Classifying hippocampal-dependent spatial strategies versus striatal-dependent response strategies to characterize circuit-specific dysfunction.
- 5Longitudinal Memory Tracking — Administering repeated probe trials across weeks to map memory persistence and forgetting in time.
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