Faculty Member - Division of Biological Sciences University of Missouri-Columbia

This depth coded image shows the location of the serotonin neurons in the Drosophila central brain. Anterior is labeled in aqua, Posterior in violet. Neurons in different clusters are labeled, and described in Sitaraman et al., 2008. The ellipsoid body (eb) is labeled for orientation. The scale bar represents 50 µm.

Research description

We study the molecular / cellular, systems, and behavioral control of learning using Drosophila. These learning mechanisms are examined in three interdependent approaches. We identify new gene function in neural systems to support learning in behavioral paradigms that we define.

Molecular / cellular mechanisms of learning. Because of the commonality of some gene function in resistance to ethanol effects on behavior and learning, we characterized the memory phenotypes of several novel ethanol sensitive mutants. We found three new genes that have learning functions in operant place learning and classical olfactory conditioning. These genes implicate novel and different processes in memory formation. We continue to characterize these mutant flies.

Neural system mechanisms of learning. Using genetic and pharmacological approaches, we found that the serotonergic system is necessary for memory formation. Indeed, we find that altering excitability of these neurons leads to memory performance levels of different strengths. Furthermore, we discovered that the serotonergic system is critical for a process that enhances memory performance after experience with unpredicted experience with negative reinforcement. We are determining the role of the serotonergic system in olfactory memory and developing tools for manipulating subsets of the serotonergic nervous system.

Behavioral analysis. We examined the role of reinforcement pre-exposure on subsequent memory acquisition. This manipulation leads to either enhancement or decrement in later memory formation in many animal models. It was an open question how reinforcement pre-exposure would alter learning in Drosophila. We found that reinforcement pre-exposure increases associative memory performance, the first example of this sort in an invertebrate animal. Furthermore, yoking experiments show that it is the lack of an accurate predictor that is important for acquisition of this effect.

Selected publications

Gioia, A., and T. Zars. 2009. Thermotolerance and place memory in adult Drosophila are independent of natural variation at the foraging locus. J. Comp. Physiol. A, 195, 777-782.

Zars, M., and T. Zars. 2009. Rapid matching in Drosophila place learning. Naturwissenschaften, 96,927-931.

Sitaraman, D., M. Zars, H. LaFerriere, Y. Chen, A. Sable-Smith, T. Kitamoto, G. Rottinghaus, and T. Zars. 2008. Serotonin is necessary for place memory in Drosophila. PNAS 105, 5579-5584.

LaFerriere, H, D. Guarnieri, D. Sitaraman, S. Diegelmann, U. Heberlein, and T. Zars. 2008. Genetic dissociation of ethanol sensitivity and learning in Drosophila melanogaster. Genetics 178, 1895-1902.

Hoyer, S.C., A. Eckart, A. Herrel, T. Zars, S. Fischer, S. L. Hardie, and M. Heisenberg. 2008. Octopamine in Drosophila male aggression. Current Biology 18, 159-167.