The seventh session started with the 24th talk of this meeting by Mirjam Appel. She told us about a mutant screen for forward and backward conditioning in aversive olfactory conditioning in Drosophila. I this setup, an electroshock that follows odor onset leads to an aversive memory (odor signals shock) and if odor offset follows electroshock offset (odor signals shock relief), an appetitive memory for the odor is formed, i.e., dependent on the timing of the electroshock with regard to the odor, in a subsequent test, the odor is either approached or avoided. She uses the same 40 fly lines in which trudy Mackay characterized gene expression using gene microarrays and which we are using for studying the heritability of mate choice. Their screen is straightforward: test all lines in both paradigms and then look for correlation between learning scores and gene expression.
The 25th speaker was Michael Schmuker from our department. He's a computational neuroscientist and presented his model on the dual pathway of olfactory coding in honeybees. With 'dual pathway' he was referring to the medial and lateral antennocalycal tract (m-ACT and l-ACT). Neurons in each pathway show similar responses to odors with m-ACT neurons being more broadly tuned and l-ACT neurons being more narrowly tuned to specific odors. His model shows nicely how a broad spread of the strangth of lateral inhibition within the antennal lobe subnetworks can explain the differences between these two neuron populations.
Ayse Yarali continued the session with her work on quantitative models of event timing in associative learning. Her starting point is the approach/avoidance learning paradigms described above in olfactory conditioning in Drosophila. Ayse took data from the activation kinetics of adenylyl cyclases (which is activated by both calcium and serotonin, but the activation is also highly dependent on the relative timing of the stimuli) in Aplysia and derived a model of cAMP production in the fly which seems to fit the inter-stimulus-interval function one can observe in behavior.The 27th and final speaker for today was Thomas Riemensberger who talked about flies without dopaminergic neurons. Lack of dopamine is lethal in flies (they don't hatch from the pupal case), so Thomas showed us his elegant strategy of restricting the lack of dopamine to the adult brain. These flies show a normal lifespan, but impaired aspects of locomotion. These flies also show increased sleep and reduced geo- and phototaxis, despite their vision being unaffected. The flies without dopamine can fixate the stripes in the Buridan paradigm, show no aversive olfactory learning but spatial learning remains largely intact. The flies have a wing-phenotype which means they don't fly.