Abstract
Stereotypies are abnormal repetitive behaviour patterns that are highly prevalent in laboratory mice and are thought to reflect impaired welfare. Thus, they are associated with impaired behavioural inhibition and may also reflect negative affective states. However, in mice the relationship between stereotypies and behavioural inhibition is inconclusive, and reliable measures of affective valence are lacking. Here we used an exploration based task to assess cognitive bias as a measure of affective valence and a two-choice guessing task to assess recurrent perseveration as a measure of impaired behavioural inhibition to test mice with different forms and expression levels of stereotypic behaviour. We trained 44 CD-1 and 40 C57BL/6 female mice to discriminate between positively and negatively cued arms in a radial maze and tested their responses to previously inaccessible ambiguous arms. In CD-1 mice (i) mice with higher stereotypy levels displayed a negative cognitive bias and this was influenced by the form of stereotypy performed, (ii) negative cognitive bias was evident in back-flipping mice, and (iii) no such effect was found in mice displaying bar-mouthing or cage-top twirling. In C57BL/6 mice neither route-tracing nor bar-mouthing was associated with cognitive bias, indicating that in this strain these stereotypies may not reflect negative affective states. Conversely, while we found no relation of stereotypy to recurrent perseveration in CD-1 mice, C57BL/6 mice with higher levels of route-tracing, but not bar-mouthing, made more repetitive responses in the guessing task. Our findings confirm previous research indicating that the implications of stereotypies for animal welfare may strongly depend on the species and strain of animal as well as on the form and expression level of the stereotypy. Furthermore, they indicate that variation in stereotypic behaviour may represent an important source of variation in many animal experiments.
Highlights
Stereotypies are commonly defined as repetitive and invariant behaviour patterns without apparent goal or function [1,2]
Previous studies using different tasks found that stereotypy level was positively correlated with measures of recurrent perseveration in C57BL/6 mice [42] but not in CD-1 mice [5,43], these two strains were used in the present study
Two C57BL/6 mice were excluded after recording the expression of stereotypic behaviour as they only performed RT compared to all other mice which performed route-tracing with bar-mouthing (RT-BM), resulting in a final sample of 44 CD-1 mice and 40 C57BL/6 mice
Summary
Stereotypies are commonly defined as repetitive and invariant behaviour patterns without apparent goal or function [1,2]. They are prevalent in many captive species, including laboratory rodents [1,2,3]. Attempts to link stereotypic behaviour with physiological or behavioural indicators of impaired welfare have produced mixed results. Jumping and bar-mouthing in laboratory mice, for example, have been suggested to develop from attempts to escape the cage [3,7,12]. Bar-mouthing level has been found to correlate positively with corticosterone levels at weaning [13], a physiological measure of stress. In another study [7], no correlation with corticosterone levels was observed
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