Fig. 2. Timeline of experiment.

First, mice were single-housed for 6 days prior to water restriction (not depicted in this timeline). Mice were water restricted for three days (corresponding to days 1 −3 on the timeline) prior to beginning the daily sucrose preference testing, also spanning the course of three days (corresponding to days 4 – 6). On the seventh day after beginning water restriction, animals were habituated to the testing apparatus in one 20-minute session. On day 8, animals underwent 5 trials of reward training, in which mice were given unlimited time to traverse the middle chamber (with clean bedding) to obtain the sucrose reward in the end chamber. On the ninth and final day, animals completed a total of 6 trials. Three of these trials occurred in the morning (termed: “refresher” in the timeline) with clean bedding in the middle chamber (as on day 8). The last three trials occurred in the afternoon (termed: “testing”) approximately 3 hours after the AM session. Prior to the testing phase, mice were randomly assigned to have the middle chamber scented with PEA, MV, or clean, unscented bedding (CB) for all three of these trials. CB, clean bedding; MV, methyl valerate; PEA, phenylethylamine.