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Electric Shock-Induced Associative Olfactory Learning in Drosophila Larvae

Research field: Learning & Memory

Johanna Pfitzenmaier, Andreas Thum

Associative plasticity is a basic essential attribute of nervous systems. As shown by numerous reports, Drosophila is able to establish simple forms of appetitive and aversive olfactory associations at both larval and adult stages. Whereas most adult studies on aversive learning employed electric shock as a negative reinforcer, larval paradigms essentially utilized gustatory stimuli to create negative associations, a discrepancy that limits the comparison of data. To overcome this drawback, we critically revisited larval odor–electric shock conditioning. First, we show that lithium chloride (LiCl), which was used in all previous larval electric shock paradigms, is not required per se in larval odor–electric shock learning. This is of considerable practical advantage because beside its peculiar effects LiCl is attractive to larvae at low concentration that renders comparative learning studies on genetically manipulated larvae complicated. Second, we confirm that in both a 2-odor reciprocal and a 1-odor nonreciprocal conditioning regimen, larvae are able to associate an odor with electric shock. In the latter experiments, initial learning scores reach an asymptote after 5 training trials, and aversive memory is still detectable after 60 min. Our experiments provide a comprehensive basis for future comparisons of larval olfactory conditioning reinforced by different modalities, for studies aimed at analyzing odor–electric shock learning in the larva and the adult, and for investigations of the cellular and molecular substrate of aversive olfactory learning in the simple Drosophila model.

funding by: DFG, SNF
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One-odor nonreciprocal training protocol reinforced by electric shock. (A) The left diagram shows the general procedure of the conditioning experiment. The remaining diagrams represent control experiments for analyzing selectively the effects of odor exposure,electric shock exposure, and handling, on BA odor preference. One-odor nonreciprocal training led to a significant decrease in BA odor preference when comparing values before (pre-test) and after training (test) for 1 (B) and 5 (D) training trials. The resulting differences (DPREF) that are shown as positive values indicate associative learning. Significance levels represent P < 0.05 (*), P < 0.01 (**), and P < 0.001 (***).

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Our shared enthusiasm drives us to unravel bolts and nuts for a better understanding of animal behavior. Many of our projects focus on neuronal mechanisms related to odor reception and odor information processing. We study neuronal networks with molecular tools, physiological measurements and behavioral experiments using free-moving animals.

All of our study organisms are insects because we strongly believe that insects offer great advantages for basic research, thereby providing significant contributions to the wide field of biological science. We work on the model organism Drosophila, and use the plethora of molecular tools to study the brain, both in larvae and adults. We investigate odor discrimination and learning in honeybees with behavioral experiments and functional imaging of brain activity; and we study several other social insect species (ants and bumblebees) aiming to close the gap between differences in neuronal representations and inter-individual variability in behavior. Inter-individual variability is an important feature of social insect colonies, promoting social decision-making and collective behavior.

The diversity of our projects reflects our belief that only a truly integrative research approach will lead to a profound understanding of brain functions, as well as of the proximate and ultimate causation of animal behavior.

For further information on specific projects, please select one of the research fields on the left.




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