Fig. 1. Experimental setup, enriched environment, and longitudinal monitoring of body weight.

(A) At an age of 5 weeks, 120 female C57BL/6JRj mice were split into three equally sized groups: 40 mice lived in ENR for 6 months, while a second group stayed in standard housing cages (STD) for 6 months, and the third group (ENR-STD) lived in ENR for the first 3 months (phase 1) and in STD for the last 3 months of the experiment (phase 2). Behavioral testing was performed with all animals in the last weeks of both phases. For quantification of adult hippocampal neurogenesis, all mice were injected with the thymidine analogs 5-iododeoxyuridine (IdU) and 5-chlorodeoxyuridine (CldU) 4 weeks before the ends of phase 1 and phase 2, respectively. (B) Image of the ENR cage system used for automated behavioral tracking of mice by RFID technology (photo credit: Susan Schilling, DZNE Dresden). (C) Schematic representation of the ENR cage depicting cage and tunnel access for the ENR group (light blue; top) and ENR-STD group (violet; bottom). RFID antenna were located around every tunnel and are highlighted in red. (D) ENR-induced reduction in body weight rebound to STD levels after returning ENR-STD mice to STD cages. Data points indicate means and SEM. Arrow marks return of ENR-STD to STD cages. Depicted P values from Brown-Forsythe test refer to housing effects. Full information on statistical tests is presented in Table 1 and data file S1.