Dynamic Integration of Space and Context in Mice

Abstract

In an animal’s territory, usually the animal recognise it and tries to defend the territory in response to social and environmental challenges. But, the neural mechanisms linking contextual information to aggression-related circuits are poorly understood. The ventral hippocampus, especially the ventral CA1 (vCA1) region, is known to play an important role in processing emotional and social contexts and may contribute to territorial behaviour. In this study, neurons that were active during a non-territory experience were permanently labelled using the TRAP2 mouse system. This allowed identification of neurons that were active during a specific time window. When the animals were later exposed to a territorial situation, many vCA1 neurons showed c-Fos expression, indicating recent neuronal activation. The number of c-Fos-positive neurons was consistently higher than the number of TRAPed neurons, which is expected because activity-dependent recombination captures only a subset of active neurons. When the two populations were compared, only a small number of neurons were positive for both markers. This may suggest that only a limited fraction of neurons that were active during the non-territory experience were reactivated during the territorial context. Behavioural analysis of territorial aggression, measured using the number of attack and chase behaviours relative to defensive behaviours, did not show a clear correlation with the proportion of double-positive neurons. However, this analysis was limited by the small number of animals and incomplete behavioural recordings. Overall, these results suggest that neuronal ensembles recruited during territorial encounters are largely distinct from those activated during prior experiences.