Olfactory conditioning in the honey bee, Apis mellifera: effects of odor intensity

Any odor-guided behavior might require generalization and/or discrimination over a wide range of odorant intensities. Proboscis extension conditioning (PEC) and electroantennogram (EAG) assays were used to investigate stimulus-intensity dynamics during olfactory processing in the honey bee. Experiments that tested generalization involved conditioning to one odorant concentration and either testing with a different odorant or with different concentrations of the same odorant. At low training concentrations, responses to either a novel odorant or to higher concentrations of the same odorant resulted in strong generalization. At higher training concentrations, significantly less generalization was observed to a novel odorant or to lower concentrations of the same odor. EAG analyses indicate that asymmetric generalization could arise due to long-term adaptation of peripheral receptor neurons. Discrimination experiments showed that relatively higher odorant concentrations associated with an appetitive reinforcer could usually be discriminated from a lower concentration that was associated with punishment, but not vice versa. Although sensory modulation in peripheral (sensory) processes might be sufficient to account for discrimination of a high from a low concentration, discrimination of low from high concentrations point to the involvement of central processes.