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Diversity, Variability, and Suboesophageal Connectivity of Antennal Lobe Neurons in D. melanogaster Larvae

Research field: Sensory processing

Andreas Thum

Whereas the ‘‘vertical’’ elements of the insect olfactory pathway, the olfactory receptor neurons and the projection neurons, have been studied in great detail, local interneurons providing ‘‘horizontal’’ connections in the antennal lobe were ignored for a long time. Recent studies in adult Drosophila demonstrate diverse roles for these neurons in the integration of odor information, consistent with the identification of a large variety of anatomical and neurochemical subtypes. Here we focus on the larval olfactory circuit of Drosophila, which is much reduced in terms of cell numbers. We show that the horizontal connectivity in the larval antennal lobe differs largely from its adult counterpart. Only one of the five anatomical types of neurons we describe is restricted to the antennal lobe and therefore fits the definition of a local interneuron. Interestingly, the four remaining subtypes innervate both the antennal lobe and the suboesophageal ganglion. In the latter, they may overlap with primary gustatory terminals and with arborizations of hugin cells, which are involved in feeding control. This circuitry suggests special links between smell and taste, which may reflect the chemosensory constraints of a crawling and burrowing lifestyle. We also demonstrate that many of the neurons we describe exhibit highly variable trajectories and arborizations, especially in the suboesophageal ganglion. Together with reports from adult Drosophila, these data suggest that wiring variability may be another principle of insect brain organization, in parallel with stereotypy.

funding by: DFG, SNF
Project Picture

Patterns and neurotransmitter properties of neurons in the larval AL as revealed by three selected GAL4 lines. A: 189Y-GAL4; mb247-GAL80 labels AL neurons (ALNs) whose cell bodies are located ventrolateral of the AL (thin arrows). B: NP2426-GAL4 displays two clusters of ALNs, ventrolateral (thin arrow) and dorsolateral (bold arrow) of the AL. In both lines ALNs densely innervate the AL and send extra processes into the adjacent SOG (asterisks), especially in NP2426-GAL4. C: NP3056-GAL4 also displays ventrolateral ALNs (thin arrow) and dorsolateral ALNs (bold arrow). Innervation appears sparse in the AL but prominent in the adjacent SOG (asterisk).

Project Picture

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.




Neurobiology Uni-Konstanz

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