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My lab:
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This day of the symposium was all about invertebrates other than honeybees. Pulitzer-winning author Bert Hölldobler started out by talking about "Multicomponent and multimodal signals in ant communication". The first part of the presentation dealed with the communication of the queens to the workers, making sure only the queen reproduces. As is the case with a large part of social insect communication, the information that a queen is present is singalled via chemical compounds spreading through the colony. The second part dealt with worker to worker communication. Most foraging ants lay a pheromone trail which other members of the colony will follow. The compound mix which makes up the pheromone contains more or less volatile individual components. The following ants re-mark the trail not with the original pheromone, but with related pheromones ecreted by glands in their legs, such that other ants can still follow the trail (or they themselves find back) even when the original trail has long evaporated. Bert called this the Hänsel-and-Gretel strategy. Another worker-worker communication example is the recruiting pheromone used to recruit nest-mates to both food and to fight other ants. The recruited ants are told by the recruiters' behavior if they should follow the trail to fight or to forage. When I asked, Bert mentioned that he sees this as a referential signal by the recruiting ants.

My good friend Bertram Gerber was next, talking about "Neurogenetics of associative function in Drosophila". Right down my alley, Bertram started out by showing how advantageous Drosophila is as a model system because of it's genetic toolset: we can express almost any manipulator of neuronal function anywhere in the fly nervous system. His talk was divided in two parts, the first one was about larval olfactory learning and the second about what he called pain-relief learning.
For larval olfactory learning, Bertram showed that mutating the synapsin gene revealed that one part (~50%) of this olfactory memory depends on this gene. Rescue experiments demonstrated that the protein coded for by the synapsin gene functions acutely, at the time of the training and that is both necessary and sufficient to express the Synapsin protein in the mushroom-bodies. Using optogenetics, they were able to replace the sucrose reward by activating octopaminergic neurons (and replace electric shock with activation of dopaminergic neurons). Finally, Bertram showed evidence that Synapsin appears to be downstream of the canonical cAMP/PKA pathway of synaptic plasticity known from classical conditioning in adult flies.
Pain-relief learning means that animals learn signals that predict the end of a painful stimulus. In the case of flies, Bertram presents flies with an odor exactly at the offset of an electric shock. If you do this, flies will approach this odor in a later test. Bertram's lab is in the process of studying where in the brain which pathways are taking place in order to form this memory. In parallel, Bertram collaborates with psychologists to study pain-relief learning in humans. He told us that despite a signal predicting relief reducing a fear-potentiated startle response, the study subjects did not rate the signal as emotionally positive. Functional magnetic resonance imaging appeared to follow more the behavior of the subjects and less their subjective rating.

Third speaker was John Hildebrand presenting work on "Neural processing of behaviorally significant odors in the antennal lobe of the moth Manduca sexta". However, the otherwise very reliable wifi connection here unexpectedly started to fail for me midway through the talk, so I lost my notes for the talk and could not cover the talk from Hanna Mustaparta on "Chemosensory coding and learning in the moth Heliothis virescens: searching for the neuronal network involved".
Posted on Sunday 13 June 2010 - 11:53:56 comment: 0
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