The function of plasticity in neural networks of the honey bee brain that process complex floral odors

SMITH BRIAN; FERNANDEZ PATRICIA; LOCATELLI FERNANDO

Beijing

Congreso; The 6th Asia-Pacific Conference on Chemical Ecology; 2011

Asia-Pacific Association of Chemical Ecologists

Natural odors are typically mixtures of several different chemical components. Changes in the composition of the mixture, by deleting or replacing components or by changing the ratios of components in the mixture, can have a significant impact on the perceptual properties of the mixture. It has been now widely shown that these types of differences separate odor “objects” that animals must identify and discriminate for their survival. The use of floral odor bouquets by honey bees is a classic example. The odor bouquets can contain many chemical constituents, which collectively give rise to the unique perfumes of many varieties of flowers both and between species. Moreover, these perfumes are distinguishable to both humans and to honey bees in behavioral experiments, which likely reflects the broad similarities in odor coding and processing in the early parts of their olfactory systems. Sensory cells transduce pure (single component) odors via expression of one, or in the case of insects two, molecular receptors among the dozens to hundreds of functional receptors in the genome. Typically sensory cells respond to a range of odorants that possess the same or similar molecular structures. Thus any sensory neuron responds to several odorants, and any odorant is encoded by different rates of activity across a subset of sensory cells that express different receptors. This combinatorial, cross-fiber coding enables the detection of a very large number of odorant molecules. The neural networks in the insect antennal lobe provide the first level of processing of these codes in the brain. These networks extract features of the odor signature such as, for example, the precise mixture of components, the temporal signature the odor plume at the antennae, and the association of the odor with important events such as food. Yet, in spite of the complex chemical composition of odor bouquets, most studies of sensory and antennal lobe processing of odors focus on single components or on mixtures that have not been systematically altered. Our work focuses on how the antennal lobes process and differentiate among complex floral odor bouquets. We have shown for simple mixtures that the antennal lobe separates these mixtures to a degree correlated with the honey bee’s ability to behaviorally discriminate the odors. Furthermore, associative and nonassociative plasticity manifested in the antennal lobe further separate the odors. We have extended this work to show that the same types of plasticity operate on more complex synthetic – and systematically varied - blends that mimic natural floral odor bouquets. This presentation will summarize this work, discuss how plasticity is implemented in the antennal lobe, how this plasticity functions in the larger brain context, and lastly on the role of plasticity in the ecology of foraging behavior.