Figure 2: Experimental timeline for the comparison of familiar and novel object conditions. (a,1) For animals exposed to novel objects, 2 animals were housed together for over 2 weeks. They were brought to the laboratory and housed there until the next day, Day 1. On Day 1, the cage lid was removed, and 2 objects were placed in the cage center about 6 inches apart. After 5 min, the objects were removed. This was repeated so that there were 3 exposures for 5 min, one hour apart. (a, 2) For animals exposed to familiar objects, a similar procedure was used, but the objects were different. (a, 3) For animals with no habituation, no objects were presented to the animal on Day 1. (b, 1) For animals exposed to novel objects, procedures on Day 2 were similar to Day 1 but the objects were different. Also, after objects were removed, one animal was perfused 90 min after object exposure began, and the second was perfused at 110 min. (b, 2) For animals exposed to familiar objects, procedures were the same as Day 1. However, object exposure occurred once, and one mouse was perfused 90 min after object exposure and the other was perfused at 110 min. (b, 3) For the no habituation group, novel objects were placed in the cage on Day 2. One mouse was perfused 90 min after object exposure and the other was perfused at 110 min.