2010 Abstract Book
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ABSTRACTS from PLENARY LECTURES (PL) SPECIAL LECTURES (SL) SYMPOSIA (S) PARTICIPANTS SYMPOSIA (PS) and YOUNG INVESTIGATORS TALKS (YIT) 1 AUGUST 3 Plenary Lecture 1 Mark Willis (Case Western Reserve University) PL1 “The Neuroethology of odor-guided flight in moths: Interaction of environment, locomotion and sensor structure determines odor-tracking behavior.” Locating important resources from long distances often requires the ability to track odors that have evaporated from their source and been distributed downstream as turbulent dynamically changing distributions of odor molecules known as plumes. Walking and flying animals perform complex maneuvers while tracking odor plumes through very different environmental conditions no matter where their sensors are positioned. Two alternative strategies may allow them to maintain contact with plumes using olfaction: (1) a spatial strategy, i.e., simultaneous comparison of odor concentrations at two locations in space using bilaterally symmetrical sensors, or (2) a temporal strategy, i.e., comparisons of odor concentrations over time. It is thought that animals rapidly navigating in three-D through turbulent odor plumes use a temporal strategy, while animals navigating slowly near surfaces use a spatial strategy. However, animals can move at a range of speeds, change their mode of locomotion, and encounter many environments. Whether an animal tracks plumes spatially or temporally is difficult to determine because the effects of sensory input, behavior, and the environment are entangled. We have experimentally-manipulated air flow in our laboratory flight tunnel to mimic turbulence experienced by plume tracking insects in different natural environments. These flows and the odor plumes generated by them have been carefully characterized using flow sensors (hot-wire anemometers) and the antennae of the insects we study as bio-detectors. Walking and flying insects tracked plumes in turbulence characteristic of their own natural environment and that of their walking or flying counterpart. Flying moths locate the odor source more often in high than low turbulence environments, and walking cockroaches are equally successful in all but the most turbulent environments. Experiments manipulating the ability of these animals to extract spatial and temporal odor information are ongoing. 2 Plenary Lecture 2 John Simmers (Université de Bordeaux, CNRS UMR 5227) PL2 “What the spinal cord tells the eyes: gaze-stabilizing eye movements driven by efference copy signals from the locomotory pattern generator in swimming Xenopus tadpoles.” All vertebrates, whether running, swimming or flying, are confronted with the effects of their locomotory actions on the ability to perceive their surrounding environment. A possible consequence of self-generated body motion is head movement that cause retinal image drift with a resultant degradation of visual information processing. In order to maintain visual field acuity, retinal image displacement is counteracted by dynamic compensatory eye and/or head adjustments that derive from the concerted actions of vestibulo-ocular and optokinetic reflexes. We have recently discovered in larval frogs(1) that intrinsic copies of rhythmic locomotor commands produced by central pattern-generating circuitry in the spinal cord are able to drive extraocular motor output patterns that are appropriate for driving compensatory eye movements during undulatory tail-based swimming. Such efference copy signalling, in which the brainstem extraocular nuclei effectively become appropriated to the spinal cord, provides a convenient substrate for driving rapid eye adjustments during locomotion, pre-empting the slower engagement of movement-encoding sensory pathways. In my talk, I will describe the experimental evidence for this novel interaction between two otherwise functionally and anatomically distinct motor systems and present recent evidence for how the intrinsic locomotory commands are conveyed to their extraocular motor targets and how these feed-forward signals are likely to be integrated with visuo-vestibular feedback information. (1) Combes D, Le Ray D, Lambert F, Simmers J & Straka H (2008) An intrinsic feed-forward mechanism for vertebrate gaze stabilization. Curr. Biol. 18, R241-243. 3 Symposium 1 "The role of chemosensation in sexual behaviors" Organizer: Yehuda Ben-Shahar (Washington University in St. Louis) Tainted love: olfactory detection of tetrodotoxin in rough-skinned newts. S 1.1 Heather Eisthen (Michigan State University) Tetrodotoxin (TTX) is used as a chemical defense against predation by a variety of organisms, including pufferfish (Fugu) and many species of newts; it is also used by some octopus and arrowworms as a venom to subdue prey. TTX is effective in these contexts because it is a potent blocker of voltage-gated sodium channels. Given its often lethal effects, it is perhaps surprising that some of the organisms that produce TTX have also co-opted it for use in intraspecific communication -- for example, it serves as an attractant pheromone in pufferfish. The mechanisms by which TTX is detected and processed as an olfactory stimulus are unknown. We are examining the behavioral significance and neural mechanisms of TTX detection in adult rough-skinned newts, Taricha granulosa. Our preliminary data indicate that in a Y-maze with flowing water, adult male newts are attracted to a source of 100 nM TTX, suggesting that the animals can smell TTX and may use it in finding or recognizing conspecifics. Using electro- olfactogram (EOG) recordings, which measure summed generator potentials, we find that TTX evokes robust responses from the olfactory epithelium in concentrations ranging from 1 nM to 1 µM. These responses are similar in shape and time course to those evoked by other odorants, such as whole-body odorants from adult male conspecifics, washings from earthworms, and mixtures of amino acids. In one experiment, we substituted choline chloride for sodium chloride in the Ringer’s solution used to bathe the olfactory epithelium during recordings. Interestingly, in the presence of choline chloride, responses evoked by TTX are abolished, but responses evoked by other odorants are unaffected. This result demonstrates that EOG responses evoked by TTX depend on external sodium, suggesting that TTX is transduced by olfactory receptor neurons using a mechanism other than the classical odorant transduction pathway. We are currently pursuing experiments to examine the possibility that TTX detection involves a modified sodium channel in the olfactory epithelium of newts. 4 Neuronal mechanisms underlying pheromone-mediated sexual behaviour. S 1.2 Tali Kimchi (Weizmann Institute of Science) Sexually dimorphic behaviors represent a robust set of innate social and reproductive responses including mating, nursing and aggression. Although theses sexually dimorphic behavioral responses represent the most extreme examples of behavioral variability within a species, the basic principles underlying the sex specificity of brain activity is poorly understood. In rodents, pheromones play a major role in controlling innate sexually dimorphic behaviors, along with substantial neuroendocrine responses. Genetic ablation of TRPC2, an ion channel crucial to the functioning of the vomeronasal organ (VNO) sensory neurons, provides a noninvasive experimental system to directly investigate the role of VNO-mediated pheromone detection in mice. TRPC2 mutant male mice displayed normal mating behavior with an estrous female. However, these mutant males also attempted to mount male intruders instead of attacking them. Recently, I have shown that TRPC2 mutant female mice engage in male-typical courtship and sexual behaviors including mounting, pelvic thrusting and ultrasonic vocalization, indiscriminately toward either a male or a female intruder mouse. Further they display reduction of female-specific behaviors, which include maternal aggression and lactating behavior. These findings demonstrate that VNO signaling plays a critical role in sex discrimination and regulation of sex-specific reproductive behaviors in males and females. We have now developed new experimental methodologies to study pheromone-evoked responses in freely-behaving laboratory and wild-caught mouse colonies, under natural biologically relevant context. I will describe our recent efforts in characterizing novel sexually dimorphic pheromone-induced behavioral and neurochemical responses using ethologically-relevant experimental approaches. 5 Taste of love: a role for the gustatory sensory system in fly courtship. S 1.3 Yehuda Ben-Shahar (Washington University in St.Louis) Sexual behaviors are complex and require sensory inputs from multiple modalities. The majority of the signals, their cognate receptors, and the cells that mediate them are still poorly understood. We use the genetic model Drosophila melanogaster to investigate how animals encode and interpret socially related signals. Here we focus on the role of the gustatory system in mediating sex-related signals in insects. We have identified a novel ligand-gated ion channel (aguesic, agu) that plays a role in chemosensory functions underlying mating behaviors in Drosophila. agu is expressed in a subpopulation of chemosensory bristles on the legs and wings that are distinct from those expressing feeding-related gustatory receptors. Moreover, agu is not expressed in the labellum, the primary organ involved in taste, and disrupting agu or inhibiting activity of agu- expressing