Development of a 3D tracking system for multiple marmosets under free-moving conditions.

Assessment of social interactions and behavioral changes in nonhuman primates is useful for understanding brain function changes during life events and pathogenesis of neurological diseases. The common marmoset (Callithrix jacchus), which lives in a nuclear family like humans, is a useful model, but longitudinal automated behavioral observation of multiple animals has not been achieved. Here, we developed a Full Monitoring and Animal Identification (FulMAI) system for longitudinal detection of three-dimensional (3D) trajectories of each individual in multiple marmosets under free-moving conditions by combining video tracking, Light Detection and Ranging, and deep learning. Using this system, identification of each animal was more than 97% accurate. Location preferences and inter-individual distance could be calculated, and deep learning could detect grooming behavior. The FulMAI system allows us to analyze the natural behavior of individuals in a family over their lifetime and understand how behavior changes due to life events together with other data.

High Salt Intake Induces Active Coping Behaviors by Enhancing the Resilience against Psychological Stress in Mice.

BACKGROUND: High salt intake increases the active coping behavior during psychological stress. Acute fear-related severe stress enhances passive coping behavior during subsequent inescapable stress. METHODS: We investigated the effect of high salt intake (2%) for 5 consecutive days on the coping behavior in C57BL6 mice which employing the tail suspension test (TST) at 1 h after the exposure to inescapable innate fear using 2,5-dihydro-2,4,5-trimethylthiazoline (TMT), a synthetic component of fox feces. By using a different mouse group, to investigated whether anxiety-like behavior was correlated with coping behavior during the TST, we performed the elevated-plus maze (EPM) test at 1 h before the TST without TMT. RESULTS: Both the distance traveled and the number of entries in the central zone of test box during TMT were negatively correlated with freezing time in both sodium- and water-intake mice. Sodium-intake increased the preference for central zone during TMT exposure, but did not change fear sensitivity and locomotor activity. Sodium-intake also prevented that TMT-induced increase in the immobility time during TST. The immobility time during TST was positively correlated with freezing time during TMT exposure in sodium-intake, but not in water-intake mice. Furthermore, the immobility time during TST in sodium-intake mice correlated with the distance traveled and with the number of entries in the central zone during TMT. Sodium intake also increased the number of entries and the time spent in the open arm of the EPM, indicating that high salt intake had an anxiolytic effect. However, neither the number of entries nor the time spent in the open arm of the EPM were correlated with immobility time during TST in sodium-intake mice. CONCLUSIONS: We conclude that a high salt intake induces active coping behavior after experiencing fear stress by enhancing stress resilience rather than by reducing the anxiety level.