Generalization

<aside> 👉 NOTE: Mice should be food-deprived for this behaviour, so check the food restriction protocol.

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Table of Contents

Animals were tested in a clear Plexiglass cage (28 cm long x 17 cm wide x 12 cm high) with a removable black opaque center divider (customized home cages).
Animals were placed into the resting chamber, at the beginning of each session. One trial included the lifting of the divider, animals entering the test chamber, and returning to the resting chamber.

Five odor sets can be used, each composed of 6 odorants: the conditioned odorant (CS), a homologous series of sequentially similar odorants (S1-S4), and a structurally and perceptually dissimilar odorant (D). Each odorant was diluted in mineral oil to achieve a target theoretical vapor-phase partial pressure above the scented dishes of sand.

Pre-training on these animals can be done using the Pre-training for digging protocol.
We used a forced-choice olfactory generalization paradigm to measure the degree to which mice generalized a learned contingency (expectation of reward) from the conditioned odorant (CS) to each of the test odorants.
Each mouse was trained over seven sequential conditioning trials in which it had a choice between a dish scented with CS (containing a 5 mg sucrose reward) and an unscented dish containing no reward.
Subsequently, X unrewarded test trials (in which the mouse was offered a choice between a dish scented with one of the test odorants and an unscented dish) were performed in a pseudorandom, counterbalanced order; these test trials were alternated with additional rewarded conditioning trials to prevent extinction of the association between the conditioned odorant and reward.
During test trials, the total time spent digging in the dish containing the test odorant within the one-minute trial period was recorded with a stopwatch.