Discrimination learning of floral odors induces plasticity in the antennal lobe

LOCATELLI FERNANDO

Saint Petersburg

Simposio; XII European Symposium for Insect Taste and Olfaction; 2011

Floral odors are highly variable combinations of several volatiles. Composition analysis shows that no two flowers are exactly alike, even examples from the same species and cultivar. In this context, pollinators must establish if a newly encountered flower is similar or different enough to a previous rewarded one, turning foraging decisions into a fine tuned generalization-discrimination task. Sensory coding must provide mechanisms for precise odor recognition, allowing perceptual stability (i.e. generalization to prevent all experiences from being independent and novel) [1]. We hypothesize that experience with odors tunes sensory processing in the antennal lobe and thereby permit odor recognition and classification of newly encountered flowers [2]. In the present work we designed artificial floral blends that mimic the components, proportions and variability of 2 natural varieties of snapdragon flowers. All designed blends share the same components. But they could be differentiated based on the relative concentration of the components, which were more similar within than between cultivars. We trained restrained honey bees using the proboscis extension response paradigm (PER). Bees were differentially conditioned using examples of both cultivars. After training we tested the bees with a new example from each cultivar that was not used during training. The duration of the PER was lower and the latency longer when an example of the non-rewarded cultivar was offered to the trained bee. Odor induced activity patterns were measured in Projection Neurons of the Antennal Lobe by calcium imaging. Consistent with behavior, results suggest that the neural network in the AL was tuned by the experience to decorrelate mixtures representing different floral varieties. Experience-dependent plasticity at the level of the Antennal Lobe may help animals categorize a newly flower as belonging to a class related to reinforcement. This kind of mechanism may allow bees a quick adaptation to a different and constantly changing environment.   [1] Barnes et al 2008. Nat Neurosci 11(12):1378-1380 [2] Fernandez et al 2009. J Neurosci 29(33):10191-10202