Odour Plume Dynamics Influence the Brain s Olfactory Code Neil J Vickers Thomas A Christensen Thomas C Baker John G Hildebrand Presented by Maggie M Eric C Heads Up Seven Up To decide whether our discussion believes Vickers et al s article is worth being published in Nature we ll play a children s game to promote anonymity Rules Every put their heads down and hands up We ll ask 3 questions and count the votes We ll then repeat this game at the end of our presentation and reveal the overall opinion if they ve changed FUN Neil J Vickers Ph D Dr Vickers currently is a Professor and Chairman of Biology at the University of Utah His lab primarily focuses on the Neuroethology of Olfaction Understanding the neural pathways that create behaviors caused by olfaction Credentials B Sc From Imperial College of Science and Technology in London 1987 Ph D at UC Riverside 1992 Postdoctoral Research Associate at Iowa State University 1993 94 Phone 801 585 1930 Email vickers biology utah edu Thomas A Christensen Ph D Dr Christensen is currently a Senior Research Scientist in the Department of Speech Language and Hearing Sciences at the University of Arizona He spent 20 years studying insect olfaction but now focuses on the human brain and its ability to processes language Credentials B S in Biology at State University of New York at Stony Brook 1979 Ph D in Neurobiology Behavior 1983 Postdoctoral fellow at Columbia University 1983 85 Contact 520 621 8618 Email tac1 email arizona edu Tom Baker Ph D Dr Baker is currently a Distinguished Professor of Entomology and Chemical Ecology at Penn State University His lab primarily focuses on understanding signal acquisition and signal transduction of insect olfaction Credentials B S in Entomology at Cornell University 1972 M S in Entomology at Cornell 1975 Ph D in Entomology at Michigan State University 1979 Contact 814 863 4435 Email tcb10 psu edu John G Hildebrand Ph D Dr Hildebrand is currently a Reagents Professor and Professor Neuroscience Chemistry Biochemistry Entomology and Molecular Cellular Biology Department Head at the University of Arizona His research primarily focuses on the understanding of the olfactory system sensory control functional organization and mechanisms of insect nervous system Credentials A B in Biology at Harvard University 1964 Ph D ini biochemistry at Rockefeller University 1969 Postdoctoral fellow at Harvard Medical School 1969 72 Contact 520 621 6626 Email jgh neurobio arizona edu Brief Olfactory Review 1 2 3 4 1Ache et al 1994 2 Ache et al 1994 3Frye Olfactory Presentation Fall 2011 4 Axel et al 2003 Context of the Olfactory System in the Vickers et al Study Studied the response of the olfactory system following exposure to a pheromone plume in male Heliothis virescens An Electroantennogram EAG was used to record the spatial and temporal responses to a pheromone plume Hypothesis Question Do precise temporal and or spatial patterns of recognizing and discriminating different odours persist when the intensity of the odour is variable Hypothesis Olfactory circuits compensate for contextual variations in the stimulus pattern with high temporal precision Experimental Method Simple breakdown of the article First Vickers et al established there were variable EAG activity at different sampling points in a wind tunnel Second male moths were fitted with an EAG monitor as a third antenna in order to evaluate how engaging in typical activity affected spatiotemporal patterns Third examined how these rapidly changing spatiotemporal patterns affect the representation of olfactory info in the glomerular circuits in the insect s brain Fourth analyzed whether projection neurons in a moth s antennal lobe are synchronized by oscillations of brain potentials known to be prominent in a moth s olfactory network Figure 1 Experiment Recording of frequency and amplitude responses to a pheromone plume at nine stationary sampling points within a wind tunnel Results B C The structure of the odor plume varied substantially at different sampling points Evidence for position dependent variation in amplitude and frequency of bursts At low wind speeds Largest EAG bursts and highest frequency fluctuations occur in the central zone of the plume At high wind speeds Larger EAG amplitude bursts in the peripheral Therefore burst amplitude generally decreased as wind speed increased Location of the largest amplitude shifted to the periphery as wind speed increased Interpretation of Figure 1 Results Antennal responses show significant variation in amplitude over the course of stimulation Very minor shifts in position of a stationary antenna relative to an odor source resulted in large differences in detected spatiotemporal pattern of odor striking the antenna In a natural airborne plume odor contacts with antennae are brief and frequent What do you think about these results Are the conclusions fair Figure 2 Experiment Male moths fitted with an EAG as a third antenna and flown upwind of a pheromone plume The amplitude and frequency of bursts were recorded as the moth was in flight Results A B Visualization of location of EAG bursts and moth flight path within a odor plume with wind speeds of 60cm s C Left males encountered odor filaments most frequently in center of plume within 6 cm of midline C Right Averaged measurements of EAG relative amplitude revealed no significant variation across plume Amplitude distribution was considerably uniform across plume D Normalized EAG amplitudes shows no significant changes in amplitude as distance from the odor source increases Interpretation of Figure 2 Results Mean EAG pulse amplitude evoked in flight is 2 3X larger than the pulse evoked at rest Data indicates the animal s own flight movements influence the detection of odor pulses striking the antenna The initial sensory representations of the odor stimulus in the brain may vary considerably depending on the animal s level of activity Do you agree or disagree with these results Did you think the experimental design was valid Are the conclusions fair Figure 3 Experiment Examine how the changing spatiotemporal patterns affect the transport of olfactory information in the glomerular circuits in the brain They used glomerular projection neurons PN and ipsilateral antenna EAG recordings with point source odor plumes in the wind tunnel Results A A 15s segment of simultaneous PN and EAG activity PN activity is tightly correlated with antennal activation B Temporal variations in