Effects of previous familiarization on novelty reactions in mice (Mus musculus)

Mice were at first familiarized with a large novel cage during either 0, 15 min, 1 h, 12 h, 24 h or 48 h. On the following day, they were observed for a 5-min period after having freely entered the previously explored cage. Forty five behavioural items were recorded as well as entrance latency, total time spent in the large cage and transitions between the cage and the nest. Results allowed us to distinguish three groups: the most familiarized mice (24 and 48 h), the less familiarized ones (naïve and 15 min) and the intermediate group (1 and 12 h). It appears that, for the most familiarized mice, there was a topographic continuity between the familiar and the novel environment.