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I printed the two SfN posters yesterday before heading to Leipzig to talk about scientific publishing. The first one will be on Mon, Oct 19, 3:00 - 4:00 PM, 478.3/FF84 - Attention deficit and hyperactivity in a Drosophila memory mutant. This is the abstract:
Action selection is modulated by external stimuli either directly or via memory retrieval. In a constantly changing environment, animals have evolved attention-like processes to effectively filter the incoming sensory stream. These attention-like processes, in turn, are modulated by memory. The neurobiological nature of how attention, action selection and memory are inter-connected is unknown. We describe here new phenotypes of the memory mutant radish in the fruit fly Drosophila.
In several different behavioral and electrophysiological assays, radish mutant flies revealed a reduced attention span, more frequent and more random alternations in choice behavior, as well as a well-defined oscillatory hyperactivity in both brain activity and behavior. Specifically, radish mutants showed impaired optomotor behavior in a walking maze, despite showing optomotor behavior in flight. In the maze, radish mutant flies exhibited more random alternations in choice behavior at each branch point than wildtype flies. Furthermore, recordings of local field potentials in the fly brain revealed a shorter attention span when the flies were presented with two competing visual patterns, as well as a more random alternation of brain activity in response to these patterns. These brain recordings also revealed a peak at ~1.6Hz in the power spectrum of the local field potentials, where no such peak could be observed in the wildtype animals. The same oscillatory hyperactivity at ~1.6Hz could be observed in turning behavior measured in tethered flight, with visual patterns surrounding the fly. These phenotypes were rescued by transgenically expressing the Radish protein in a mutant background during fly development, but not in the adult. In addition, administration of a drug commonly used to treat Attention-Deficit Hyperactivity Disorder (ADHD) in humans, methylphenidate (Ritalin) also rescued the optomotor behavior, the reduced attention span and abolished the ~1.6Hz hyperactivity in treated flies.
We conclude that the circuits defined by radish expression in the fly brain are involved in modulating the tempo of stimulus selection and suppression. It remains to be found out if methylphenidate also rescues the radish memory defect. A failed rescue would indicate that the phenotype discovered here is not the cause for radish’s memory defect. Our findings allow for the first time to study how action selection is modulated by the interplay of external stimuli, attention and memory in a genetically tractable model organism.

sfn2009_adhd.jpg
The second poster is the one where SfN classified fruit flies as rodents, on Tue, Oct 20, 8:00 - 9:00 AM, 580.13/GG39 - Mechanisms of plasticity in simple taxis behaviors in Drosophila. Also here the abstract:
Like the proverbial moth drawn to the candle flame, the fruit fly Drosophila also stereotypically approaches light sources. This positive phototaxis is the archetypal example of hard-wired input-output behaviors. However, it has long been known that defects to the wings of the fly, either by mutation or by damage, reduce not only phototaxis but also geotaxis in walking Drosophila. If these behaviors are so hard-wired, how can manipulating an unrelated organ affect them? Using the classic countercurrent photo-/geotaxis essay developed by Seymour Benzer, we tested the hypothesis that instead of taxis being a simple matter of stimulus and response, there may be a central decision-making stage which is influenced by the wing manipulations. We discovered that the phenomenon of reduced taxis in flies with manipulated wings is very robust. The reduction in photo-/geotaxis can be observed not only in several different strains of wild type flies, but also in flies with white eyes, in strains which fail in multiple learning paradigms and in flies with impaired mushroom-body function. However, flies with wings deformed by mutation (and thus unable to fly) did not reduce their taxis any further. This results suggests that the ability to fly and not injury or pain determines the reduction in photo-/geotaxis. Experiments without guiding stimuli (walking horizontally in the dark) showed that the decrease is due to central processes and exclusively observed in response to the eliciting stimuli. Consistent with our hypothesis, our results suggest that there are dedicated circuits in the nervous system of the fly which monitor the fly’s ability to fly and modulate its walking activity depending on this status.


sfn2009_taxis.jpg
So if you're at SfN, drop by our posters and say hello!
Posted on Wednesday 14 October 2009 - 16:55:27 comment: 0
Drosophila   ADHD   taxis   phototaxis   SfN   meeting   


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