Emotional perceptions in mice: studies on judgement bias and behavioural habituation

This thesis aimed at developing a better understanding on how mice perceive their own emotional state. Next to extending on previous research on the adaptive capacities laboratory mice, we aimed at approaching the emotional perceptions of mice by establishing a behavioural test for the assessment of judgement bias. Adaptive behaviour translates into the waning of a behavioural response over time (i.e. behavioural habituation). Evaluation of behavioural habituation therefore offers a valuable “behavioural tool” to investigate changes in emotional assessments of a given stimulus in animals. The results of this thesis show that mice differ significantly regarding their ability to adapt to challenging conditions. Further, to better understand whether such behaviour might reflect the animals’ perception of its own emotional state we aimed at developing a judgement bias test for mice. A judgement bias results from an either more positive or more negative interpretation of an ambiguous stimulus (a stimulus with uncertain value).Negative emotional states induce a more negative interpretation while positive emotional states induce a more positive interpretation of the same stimulus: the glass is either half full or half empty. This thesis supports the idea that odour conditioning tests can be useful in investigating judgement bias in mice, although some methodological issues remain to be solved in future experiments. In addition to behavioural observations, different physiological and central nervous parameters were investigated in order to get a first indication of the underlying mechanisms that may regulate emotional perception in mice. From both the findings on mouse behaviour and at the central nervous level in the present thesis and previous work it can be concluded that a lack of behavioural habituation might be the result of an impaired cognitive control of emotional processes. Such a characteristic seems to have a clear genetic component since environmental challenges alone did not result in a persistent impairment of habituation in mice. From that it can be concluded that impaired habituation might be indicative of exceeded adaptive capacities and might be a valuable “behavioural tool” to investigate emotional dysfunctions in animals. In addition, brain area’s related to emotion and cognition seem to be involved in the expression of judgement biases as well, supporting the notion that the measurement of judgement biases in mice might provide more information on the animals’ perception of its own emotional state and, thus, first steps have been taken in establishing methods for gaining a better understanding of the (dys)regulation of emotions in mice and, hence in the management of their welfare