XVI International Symposium on Olfaction and Taste - ecro

<strong>XVI</strong> <strong>International</strong> <strong>Symposium</strong> on Olfaction and Taste
Poster session I Poster #7
Parallel odor processing in the honeybee favors synaptic coincidence coding
Martin F Brill 1 , Isabelle Reus 1 , Tobias Rosenbaum 1 , Martin P Nawrot 2 and Wolfgang Rössler 1
1 Biozentrum, University of Würzburg, Behavioral Physiology & Soziobiology, Würzburg, Germany
2 Institute of Biology, Free University of Berlin, Neuroinformatics & Theoretical Neuroscience, Berlin, Germany
martin.brill@biozentrum.uni-wuerzburg.de
Honeybees possess an elaborated olfactory system and a rich diversity of odor guided behaviors. Information from
olfactory receptor neurons (ORNs) on the antennae is transferred to the glomeruli in the antennal lobe (AL). Two
separate uniglomerular projection neuron (PN) output-tracts, the medial and the lateral antennal lobe protocerebral tracts
(m- and l-APT), project to higher-order centers in the mushroom bodies (MB) and lateral horn. This dual olfactory
pathway is a unique feature in Hymenoptera (Rössler and Zube 2011, ASD 40:349; review: Galizia and Rössler, 2010
Ann Rev Entomol 55:399).
Using multiple wire electrodes (adapted from Strube-Bloss et al. 2011, J Neurosci 31:3129) and a custom-built multi-unit
recording setup, we simultaneously recorded and analyzed responses of m- and l-APT PNs. To trace the electrode
recording sites, we developed a double-labeling technique to 3D-reconstruct neuronal tracts and electrode positions.
Simultaneous recordings from multiple units of both tracts revealed that m- and l-APT PNs respond to a similar set of
general odors, pheromones and behaviorally relevant odors. L-APT responses were faster and stronger indicating strong
PN recruitment and less accurate odor-quality coding. Responses from m-APT units had longer latencies, showed weaker
responses but more complex temporal firing patterns indicating weak PN recruitment, but high accuracy for identity
coding. This suggests that the dual olfactory pathway supports parallel odor processing and, potentially, coincidence
coding at the level of MB intrinsic neurons (Kenyon cells, KCs). This is supported by odor specific differences in
temporal overlap and latency differences between both tracts as calculated with the n-shift algorithm (Nawrot et al. 2003,
Biol Cybern 88,321). Parallel processing and coincidence coding of different features from similar odors via two APTs
likely enhance the odor coding capacities in this highly olfactory insect.
Supported by DFG SPP 1392.
<strong>Symposium</strong> 1 “The other noses – the vomeronasal organ, the septal organ and the Grüneberg ganglion” Saturday 23
June
The other nose : the Grueneberg ganglion
Marie-Christine Broillet
University of Lausanne, Department of Pharmacology and Toxicology, Lausanne, Switzerland
mbroille@unil.ch
In mammals, the most recently discovered olfactory subsystem, the so-called Grueneberg ganglion (GG), is present at the
tip of the nose, close to the opening of the naris. This organ was first described by Hans Grueneberg in 1973, as a
'ganglion' of unknown function. With the histological methods available at the time, Grueneberg concluded that this
ganglion-like cell mass might belong to the complex of the Nervus terminalis. These cells were “rediscovered” in 2005
thanks to the inspection of whole-mount specimens from one particular gene-targeted mouse strain called OMP-GFP.
These mice express GFP as a histological reporter under the control of the OMP promoter. OMP (olfactory marker
protein) is a mature olfactory-sensory neuron-specific marker. In memory of the original work of Grueneberg, this
structure kept its original name. The GG is an arrow-shaped neuronal structure at the anterior end of the nasal cavity that
lines both sides of the nasal septum. The paired organ is located in a shallow depression of the cartilage. In an adult
mouse, from 300 to 500 cells can be found in each GG. It has been recently shown by a variety of technical approaches
that the GG is implicated in thermo- and chemo-detection with a specific involvement in alarm pheromone (AP) sensing. A
GG comprises two populations of cells : ensheating glial cells and neurons bearing multiple primary cilia, putative site of
sensory transductions. Membrane proteins that might be important for the specific chemosensory function taking place in
this ganglion from birth on: danger detection via AP recognition have now been identified. AP evoked calcium
responses in GG neurons in vitro and induced freezing behavior in vivo, which completely disappeared when the GG
degenerated after axotomy. Chemosensing by the GG is a typical example of how the nervous system has adapted to
sense and react to a very important social cue. AP sensing is an instinctive or innate behaviour involved in natural
selection.
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