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Most organisms rely on their olfactory system to detect and analyze chemical cues in the environment, cues which are subsequently utilized in the context of behavior, such as finding a partner, finding food source and avoiding predators. The basic layout of the first olfactory processing center in insects is the antennal lobe which represents an analogous structure to the olfactory bulb in vertebrates. Odors are encoded by specific ensembles of activated glomeruli (the structural and functional units of the bulb-lobe) in a combinatorial manner. However, a comparison of the transformation of odor representations between input to the antennal lobe and output to higher brain centers yields a complex and contradictory picture. The question of how odors are processed is accordingly open. Local interneurons (LNs) in the antennal lobe may provide the neuronal substrate of this computation and represent the focus of our study. LNs of the antennal lobe represent an enigmatic element of early olfactory coding in the CNS of insects. These neurons have all their projections restricted to the antennal lobe and form wide-field arborizations within most glomeruli. The majority of LNs appears to use γ-aminobutyric acid (GABA) as a neurotransmitter, indicating that they form a lateral multi-level inhibitory network modulating the olfactory signal within the antennal lobe. In addition, excitatory cholinergic LNs form a dense network of lateral excitatory connections between different glomeruli assumed to boost the antennal lobe output. Furthermore local interneurons of different types are connected via electrical synapses resulting in a rather complex network. Using techniques ranging from neurogenetics to neurophysiology and behavioral studies in the fruit fly Drosophila melanogaster, we will investigate the function of different types of LNs in the formatting odor representation in the antennal lobe of the adult and the larva.
last updated on 2014-09-13