Measures
Thigmotaxis: swimming round the wall
Every animal starts at the wall. Some never leave.
In their first trials, animals naturally swim along the wall looking for a way out (the original notes describe exactly this). If they keep doing it, it can point to anxiety or a failure to learn the task, and the 1999 essay names thigmotaxis as one of the problems to minimise.
Why it matters
Thigmotaxis means staying near the wall; it often reflects anxiety or not yet understanding the task.
More detail
Thigmotaxis that falls across trials may reflect normal adaptation, whereas persistently high thigmotaxis may suggest stress or anxiety, failure to understand the task, sensorimotor impairment or lack of motivation. The band defaults to 20% of the pool radius.
Thigmotaxis was proposed and validated as an index of anxiety in mice (Simon et al., 1994), and anxiolytic drugs suppressed it in rats (Treit and Fundytus, 1988). It does not necessarily mean a lack of spatial ability. Time-accumulated measures such as Gallagher proximity or % time around the target do not allow fair comparison between thigmotactic and non-thigmotactic subjects; heading angle and time slices do.
Thigmotaxis (THGTIME%)
Thigmotaxis is time spent near the wall. Early wall-hugging is often adaptation; if it persists it may reflect stress or anxiety, not understanding the task, sensorimotor impairment or low motivation.
More detail
Outputs are % path and % time in the thigmotaxis band and the angular span (360° per circuit). The band (diagonal shading on plots) defaults to 20% of the pool radius, adjustable in ‘Advanced’, and you can re-analyse.
Compare thigmotactic subjects with heading angle, time slices and Gallagher by segment rather than whole-trial Gallagher or close-area measures. Brief poolside movement should not necessarily be read as thigmotaxis or failure to locate the target.
Questions people ask
How do I interpret thigmotaxis, and how do I compare thigmotactic subjects fairly?
Thigmotaxis is the tendency of an animal to stay close to the walls of an arena, often called 'wall-hugging'; in the water maze it means swimming in the outer ring next to the pool wall instead of searching the open water. A little wall-hugging in the first trials is normal while animals adapt; if it carries on, it may reflect stress or anxiety, not understanding the task, a sensory or motor problem, or low motivation. HVS Image reports the percentage of time and of path spent in a band next to the wall. To compare wall-hugging animals fairly, use heading angle, time slices and Gallagher by segment rather than whole-trial Gallagher or close-area measures.
More detail
Thigmotaxis is the tendency of an animal to stay close to the walls of an arena, often called 'wall-hugging'; in the water maze it means swimming in the outer ring next to the pool wall instead of searching the open water. It is a natural anxiety-related response to an open, unfamiliar space, so it is widely used as an index of anxiety and as a check on whether a subject is engaging with the spatial task. HVS Image measures it in a thigmotaxis band (annulus) next to the wall, by default the outer 20% of the pool radius (set as the ratio of thigmotaxis radius to pool radius in Advanced, re-analysable later, and shown with diagonal shading on the path plot). It reports % time and % path in the band (THGTIME%, THGPATH%) and the angular span swept round the pool (360° per circuit), both in total and for the largest episode. High values mean the subject spent much of the trial at the wall and little searching the open water; values that fall over training indicate the subject has learned to leave the wall. Early thigmotaxis is usually adaptation; if it persists it may reflect stress or anxiety, not understanding the task, sensorimotor impairment or low motivation. Because wall-hugging lengthens latency and path and dilutes whole-trial proximity, compare thigmotactic subjects with heading angle, time slices and Gallagher by segment rather than whole-trial Gallagher or close-area measures.
Going deeper
Behaviour identification counts only genuine thigmotaxis: repeated crossings of the pool that touch the wall ('bouncing off the walls') and staying still at the edge are excluded from the span measures. It also separates Thigmotaxis with Incursions (wall-following broken by short excursions into the pool) and Thigmotaxis with Exploration (wall-following combined with wider search), which helps distinguish a subject that is starting to search from one that never leaves the wall. Related measures are KELLY_sc (time before breaking away from the poolside) and BLOKLND1 (quadrant time excluding the thigmotaxis band). The band width changes the values, so keep it constant within a study and report it. Thigmotaxis is a validated anxiety index in rodents (Simon et al., 1994, doi:10.1016/0166-4328(94)90008-6; Treit & Fundytus, 1988, doi:10.1016/0091-3057(88)90413-3); in human VR it is less well characterised, so interpret it with care.
See also thigmotaxis in Morris water maze analysis on hvsimage.com.
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