Effects of enrichment removal on cognitive judgement bias of mice: a comparison of two paradigms.

Cognitive judgement bias (CJB) tests have become indispensable for assessing animal emotions. However, the methodology can vary profoundly. In mice, for example, approaches based on vision, spatial orientation and olfaction have all been used. Yet, the impact of such differences for test outcomes remains largely unexplored. Therefore, we aimed to assess the role of methodological variations for CJB test results by applying two different paradigms for mice: one using visual cues displayed on a touchscreen and another using spatial cues in form of different tunnel lengths. Mice were trained in either paradigm. Upon successful training, the enrichment was removed from their cages to induce differences in affective state. Thereafter, animals were tested for their CJB. Anxiety-like behaviour and faecal corticosterone metabolites (FCMs) served as additional indicators of affective state. Against our expectations, we did not detect effects of enrichment removal on CJB in any paradigm. Likewise, no effects on anxiety-like behaviour were found. By trend, animals showed increased FCMs after enrichment removal. We discuss potential reasons for these findings, focusing on the possibility that the enrichment removal effect might have been too weak. Overall, the influence of methodological characteristics such as cue modality on CJB test results remains an important focus for future studies.