Behavioral and psychological mechanisms of olfactory learning in the honey bee, Apis mellifera

A variety of factors could influence how animals learn and generalize among stimuli beginning with (1) limitations of the sensory system to (2) changes within the central nervous system due to physiological or genotypical limitations. For example, several studies have identified a significant amount of inter-individual variability in olfactory learning performance in the honey bee. This variability could be due to internal factors associated with age or caste-specific alteration of motivational state. Results from the first study indicate that when genotype is not manipulated, neither age nor caste had an effect on motivational state or discrimination learning performance. Therefore, the focus of research was shifted to an investigation of other factors that govern olfactory learning, beginning with an examination of stimulus processing in the peripheral nervous system.; Electroantennogram (EAG) analyses of sensory interactions between pheromonal and non-pheromonal odorants provide evidence against purely labeled-line coding for these odorants. Thus, broad-based cross-fiber coding for these odorants could at least in part explain behavioral phenomena such as overshadowing wherein response to an odorant is lower if a subject was trained to a mixture containing that odorant than if the subject was trained to the pure odorant only. One substantial finding of the EAG study was the dramatic effect of odor concentration. Therefore, the next set of experiments were focused on the effect of odor concentration on behavioral phenomena such as stimulus generalization. Results from this study indicate that sensory modulation in the antennal level as a result of recent experience could influence patterns of generalization to novel concentrations. However, such changes in sensitivity of sensory neurons in the peripheral nervous system could not account for all kinds of experience. Therefore, the last set of experiments were aimed at investigating the effect of central effects such as the role of inhibitory interactions within the antennal lobes (AL) of the bee brain on stimulus generalization. The AL was pharmacologically altered such that inhibition was either enhanced or reduced. Results from these pharmacology experiments suggest that learning and stimulus generalization vary depending on the environmental factors operating on the AL at different times of year.