Chaining in MWM refers to a search pattern in which the animal swims in a ring at a fixed distance from the wall, typically corresponding to the platform’s radial distance. This behavior reflects a non-spatial, egocentric strategy that does not rely on allocentric spatial cues. It is often mediated by procedural learning systems such as the dorsolateral striatum, rather than the hippocampus, which supports spatial memory.

Importantly, chaining can occur even when an animal performs well on commonly used metrics such as latency, as an animal with a circling search strategy may progressively learn the distance of the platform from the poolside, and then use chaining to find the platform much faster than in initial learning trials.

Unlike other tracking systems, HVS Image gives pool circling and chaining-specific analysis, to provide critical information about how the animal went about solving the task. These allow you to differentiate animals that are spatially impaired but still applying structured, non-spatial strategies (e.g., in models of Alzheimer’s disease or stroke) from those showing random or disorganized search patterns, which may reflect broader cognitive or motivational deficits.

It’s important to note that chaining could indicate any of the following:
– In a probe trial, after full training, chaining typically indicates that spatial learning is impaired or absent (e.g. due to AD model or lesions in the hippocampus or entorhinal cortex).
– It could also indicate that experimental conditions are such that strong spatial cues are lacking – in which case adjustments need to be made if spatial learning is of interest.
– In learning trials, it may indicate that learning is still at an early stage, and the animal has not yet formed spatial associations.

Tracking pool circling and chaining across trials helps map the transition from non-spatial to spatial strategies, or reveal a failure to make that transition.

In probe trials, chaining animals typically continue to swim at the same radius, without focusing their search on the correct spatial location. Their time in the target quadrant is usually near chance, and any platform crossings are incidental. In this context, chaining analysis helps explain poor spatial performance as the result of a non-spatial but deliberate search strategy, not just random or aimless swimming.