Association between exploratory activity and social individuality in genetically identical mice living in the same enriched environment

Abstract

Abstract-We previously reported that inbred, genetically identical mice living in one enriched environment develop individual behavioral trajectories, indicating increasingly different levels of spatial exploratory behavior as quantified by roaming entropy. Cumulative roaming entropy (cRE) correlated positively with adult hippocampal neurogenesis, a type of plasticity involved in the flexible integration of new information into existing contexts (Freund et al., 2013). The study on which we report here was done in parallel to that first experiment, but here we acquired detailed observational data on the behavior of individual mice. Roaming entropy (RE) was again assessed in real-time with an antenna-based system over the entire experimental period of 3 months. Compared to the least active mice in the enclosure (low number of antenna contacts), the most active animals showed tendencies of increased socially interactive behavior in the final observation block whereas least active mice displayed more self-related behavior (non-social local exploration and play). When looking at roaming behavior, we discovered that RE correlated negatively with latent factors representing social exploratory and non-social exploratory and play behavior. Adult neurogenesis could not be studied in the present cohort but we do know that under identical conditions, cumulative RE correlated positively with adult hippocampal neurogenesis. We can thus hypothesize that the mice with more exploratory experience in terms of areal coverage (as quantified by RE) and related greater levels of adult hippocampal plasticity, might also be the ones that were less involved in interactions within the group and, hence, more individualistic. While this remains to be confirmed experimentally, the present data suggest that the described mechanism of individualization, which has previously been shown to be hippocampus-dependent, has a social component.

Novel intrathecal and subcutaneous catheter delivery systems in the mouse

“…Additionally, many behavioral assays utilize the hindpaw in order to assess phenotypes such as pain, motor function, weight-bearing, locomotion, and exploratory behaviors (Gregory et al 2013; Pratt et al 2013; Pertici et al 2014; Freund et al 2015). For these reasons, a sustained peripheral drug delivery system is required in order to accurately study the physiology and behavior of neurological diseases in a mouse model.…”

Early-life environmental enrichment generates persistent individualized behavior in mice

“…We have previously shown that behavioral individualization in ENR can be detected using roaming entropy (RE) as a measure of territorial coverage and spatial exploration of the environment by individual mice 9,10 . Using the longitudinal mouse activity data obtained from the RFID recordings in the ENR cage, we calculated REs for the 40 mice of the ENR group and analyzed the development and stability of individual behavior during the six months of ENR housing.…”

“…We have previously shown that environmental enrichment (ENR) promotes the development of behavioral variability between inbred C57BL6/JRj mice and proposed that ENR could be used as a tool to study brain individualization [9][10][11] . In those experiments, inter-individual differences among inbred mice emerged when they were housed in the same ENR cage, i.e.…”

Machine vision methods for analyzing social interactions

“…Nevertheless, RFID tags have been used to reliably identify individuals in combination with video data (Weissbrod et al, 2013). Additionally, while RFID alone does not provide sufficient spatial resolution to identify social behaviors, it does provide a method to collect long-term information (with much lower storage costs than video) about animal position (Freund et al, 2013(Freund et al, , 2015Perony et al, 2012). However, the smallest RFID tags currently available, 1 mm×8 mm and 30 mg, are still very large relative to insect model systems.…”