The olfactory memory of the honeybee Apis mellifera. II. Blocking between odorants in binary mixtures.

Proboscis extension conditioning of honeybee workers was used to study the processing of odorants when bees were conditioned to binary mixtures. Responses to a set of pure floral odors and pheromones after conditioning have already been described. When bees are conditioned to certain mixtures of odorants, the response to both components is equal to that when they are tested alone. However, mixtures of an aliphatic aldehyde and an alcohol elicit asymmetric response patterns; that is, the response to the aldehyde is much stronger than that to the alcohol. A bee's response to the alcohol after it had been trained in an aldehyde background is significantly lower than when the bee is trained to respond to the same alcohol in the background of another odorant. Such response patterns are not necessarily caused by a behavioral decrement resulting from a compound-unique perceptual effect produced by the mixture. Furthermore, studies of blocking show that behavioral acquisition in response to one component can be hindered or blocked by pretraining with the other component. These results suggest that honeybees can perceive the individual components of some binary mixtures. The similarities in neural processing in olfactory systems of vertebrates and invertebrates mean that such studies could elucidate behavioral mechanisms of olfaction in a wide phylogenetic spectrum of animals.

The Olfactory Memory of the Honeybee Apis Mellifera: I. Odorant Modulation of Short- and Intermediate-Term Memory After Single-Trial Conditioning

In the first 15 min after a single learning trial the olfactory memory of the honeybee, Apis mellifera, proceeds through different processing phases during which time the memory is differentially sensitive to a cooling treatment that causes amnesia. During learning about floral odours in a natural situation, several decisions would normally be made about floral choice within that period. In order to study these phenomena in more detail, single-trial proboscis extension conditioning to different odorants was used. Several stimulus-specific effects on memory consolidation in the honeybee are shown. From previous experiments it was predicted that certain odorants would be more salient conditioning stimuli. This result is confirmed. Second, generalization from the conditioned odorant to a different odorant depends on the conditioned odorant and the time postconditioning. In some combinations, responses to a novel odorant are significantly stronger than responses to the conditioning odorant after memory consolidation. These data indicate that memory recall in the honeybee, as it is evidenced by proboscis extension, is sensitive to several aspects of stimulus identity and presentation. The acquisition and recall processes are therefore much more dynamic processes than realized previously.