Figure 1. Schematic of the learning and relearning protocol.

After habituation of 20 min per day for 3 days, animals in different groups were subjected to odor learning (blue) and relearning (red) with and without anesthesia. Circles indicate placement of animals in the behavioral testing chamber for 20 min, the first 5 min of which were recorded and quantified for odor-smelling behavior. Squares indicate termination of subsets of animals for histology measurements. Learning involves exposure to either a pure odorant (Odor A) or a mixture of two pure odorants (Odor AB). Relearning involves exposure to the same odorant(s) alongside either a different novel odorant (Odor B) or one of the components in the mixture. Behavioral tests involve forced-choice recognition among four beads, two of which are scented with experimental odorants (Odor A, Odor B, or Odor AB) and the remaining two are unscented background beads from the animals’ home cage.