In Morris water maze, thigmotaxis is wall-hugging behavior, where the subject swims around the edge of the pool close to the pool wall. It’s often interpreted as a sign of anxiety or stress, or, in early trials, unfamiliarity with the environment.

Thigmotaxis that is seen in early learning but then decreases across trials may reflect normal adaptation, whereas persistently high thigmotaxis may suggest:

• Stress or anxiety – preventing behavioral flexibility and exploration.
• Failure to understand the task – if the subject has not learned that there is a hidden platform to find or that escape is possible by searching the pool, they may persist in staying close to the edge of the water, where an exit may seem more likely to be found.
• Visual, proprioceptive, or vestibular impairments – sensorimotor impairments may prevent the subject from processing or integrating spatial cues effectively, leading to wall-hugging to maximise sensory input from the wall.
• Lack of motivation or learned helplessness – in models such as depression or chronic stress, animals may disengage from the task early and stop exploring, reverting to thigmotaxis.

In the HVS Image system, the percentage of the trial duration spent in thigmotaxis and the percentage of the path in thigmotaxis are both automatically calculated for each trial, and available for you to include in your results export if of interest.

It’s important to note that thigmotaxis does not necessarily suggest a lack of spatial or other cognitive ability, but may prevent abilities being assessed accurately by commonly used measures.

In order to compare subjects or groups of subjects where some have a significant amount of thigmotaxis and others don’t, it’s therefore necessary to go beyond common measures such as latency and path length in learning trials (which is likely to be increased for thigmotactic subjects), or time in target quadrant or platform crossings in probe trials (which is likely to be decreased for thigmotactic subjects). Even more sophisticated measures such as Gallagher proximity measures or percentage time immediately around the target area will not allow fair comparison of spatial learning or other strategies between thigmotactic and non-thigmotactic subjects. The following, however, will enable fair comparison of spatial and other cognitive abilities:

• Heading angle – for subjects who start well and switch into thigmotaxis later (for example if demoralised or distracted after not finding the platform quickly, including not finding it where expected in probe or reversal learning trials), heading angle provides an excellent indication of spatial memory, showing how directly the subject heads towards the learned location.
• Time slices – slicing trials by time allows you to remove early or late thigmotaxis and analyse the part of the trial where the thigmotactic subjects reveal their cognitive abilities, using measures such as latency, path length, time in target quad, platform crossings, Gallager proximity measures and others (applied just to the non-thigmotactic part of the trial). You might consider whether to compare these with the same time slice of non-thigmotactic subjects’ trials, or with the same-length initial portion of non-thigmotactic subjects’ trials.
• Gallagher by segment – this gives you the average distance from the target for each second of the trial, allowing thigmotactic parts of the trial to be cut away and the parts where exploration or memory are demonstrated to be kept (use with time slices in order to do that automatically).

In HVS Image, the thigmotaxis band is shown on the water maze path plots using diagonal line shading.

By default the width of the band is 20% of the pool radius; you can adjust the width to suit your experiment, and re-analyze using different widths if desired.

You can see examples of papers using or accounting for thigmotaxis at https://scholar.google.com/scholar?q=thigmotaxis+%22HVS+Image%22