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373 Symposium Olfactory Bulb ComputationsAN ACCOUNT OF ODOR DISCRIMINATION TIMES IN THEMAMMALIAN OLFACTORY SYSTEMMargrie T. 1 1 Physiology, University College London, London, UnitedKingdomRecent behavioral experiments in rodents indicate that odordiscrimination is rapid, occurring within a single sampling bout but thatthe overall time taken depends on stimulus similarity. In vivoelectrophysiological and population imaging data in rodents show thatthe activity of mitral cells in the olfactory bulb (OB) is modulated by asniff-coupled subthreshold oscillation. This paper addresses thequestion of whether measured OB action potential (AP) latencies couldaccount for the speed and similarity-dependence of odor discrimination.Using measured mitral cell input resistances, AP thresholds, odorevokedAP rates and latencies, we constructed an OB model of realisticsize (50 000 mitral cells [MCs]) that showed all the hallmarks ofpublished OB properties. Stimulus separation times and their similaritydependencewere assessed using a template-matching scheme reliant onAP latencies. In this scheme very different stimuli were accuratelyseparated within 10 ms after odor onset (100% accuracy 10 ms afterMC firing onset; A vs B). However successful separation of binarymixtures required substantially longer (87.5 ± 5.8% accuracy, 80 msafter onset of MC firing for 0.4A/0.6B vs 0.6A/0.4B). The separationtime was critically dependent of mixture similarity (52.8 ± 3.0 ms/logunit stimulus similarity; 90 ms longer for most similar odor mixturesthat were still discriminated [>85%]). These data indicate that thetemporal properties of the onset patterns of MC activity may accountfor the stimulus dependence and overall time course of olfactoryprocessing.374 Slide Clinical ChemosensorySMELL TESTING AND DATSCAN IMAGING IN DIAGNOSINGIDIOPATHIC PARKINSON'S DISEASEDeeb J. 1 , Shah M. 1 , Mohamed N. 1 , Findley L. 1 , Hawkes C. 1 1 Smell &Taste Research Unit, Essex Neuroscience Centre, London, UnitedKingdomObjective: To compare the value of smell testing versus dopaminetransporter SPECT (DaTScan) in the diagnosis of early IdiopathicParkinson's Disease (IPD). Background: There are no specific tests forIPD and errors of diagnosis occur in 10-25%. DaTScan has highsensitivity for IPD but cannot distinguish parkinsonian syndromes.Olfactory identification is impaired in more than 80% of patients withIPD but likewise has low specificity. Method: We recruited 30 newlydiagnosed, drug naive IPD patients from the neurology clinic with meandisease duration of 2.2 years (1-7 years) and mean Hoehn & Yahr stageof 1.7 (1-3). All conformed to the UK PD Brain Bank Criteria step1 andscored a minimum of 27/30 on Minimental State Examination. Thefollowing tests were used: (1) UPSIT-item 40. (2) Olfactory eventrelated potentials(OERP) to H2S using the Burghart OM2 Olfactometer.(3) (123 I)-FP-CIT DaTscan. For Controls, we used 245 subjects forUPSIT and 70 of these for OERP. A value exceeding 2 SD, ageadjustedwas considered abnormal. Results: Abnormal DaTScan wasfound in 26/30 IPD (86%). UPSIT results were abnormal in 20/30 IPD(66%). OERP was recordable in 21/30 of whom 2 had abnormallatency. Conclusion: This preliminary analysis suggests that bothDaTScan and UPSIT are of diagnostic value in early IPD but theymeasure different aspects of the disease. OERP has low sensitivity inearly IPD. UPSIT may provide a simple, inexpensive but possibly lesssensitive screening test in an early case.375 Slide Clinical ChemosensoryALTERED CHEMOSENSES IN PARKINSON´S DISEASEMuhammed N. 1 , Deeb J. 1 , Shah M. 1 , Findley L. 1 , Hawkes C.H. 1 1 Smell& Taste Research Unit, Essex Neuroscience Centre, London, UnitedKingdomBackground: According to Braak et al (2003) the first lesions inIdiopathic Parkinson´s Disease (IPD) appear in the olfactory bulb andthe dorsal nuclear complex of IX and X. Aim: To evaluate the olfactoryand taste function in patients with early IPD. Methods: 51 patients witha clinical diagnosis of early-stage IPD (mean Hoehn & Yahr stage =1.6), conforming to the UK PD Brain Bank Diagnostic Criteria step 1and scoring at least 27/30 on Mini Mental State Examination. Allreceived the UPSIT-item 40 and taste threshold assessment with theRion TR-06 Electrogustometer. The same tests were performed on 46healthy controls (HC). Results: Mean UPSIT scores were 32.9/40 forHC vs 19.8/40 for IPD group (p < 0.001). Taste threshold for the chordatympani area was 11.06 dB for HC vs 20.08 dB for IPD (p < 0.001). Forvallate papillae area 13.5 dB in HC vs 19.9 dB in IPD group (p
377 Slide Clinical ChemosensoryCOMPUTATIONAL MODELING OF NASAL AIRFLOW ANDODORANT TRANSPORT IN PATIENTS WITH CHRONICRHINOSINUSITISZhao K. 1 , Cowart B.J. 1 , Pribitkin E.A. 2 , Rawson N.E. 1 , Rosen D. 2 ,Scherer P.W. 3 , Klock C.T. 1 , Vainius A.A. 1 , Dalton P. 1 1 MonellChemical Senses Center, Philadelphia, PA; 2 Otolaryngology-Head &Neck Surgery, Thomas Jefferson University, Philadelphia, PA;3 Bioengineering, University of Pennsylvania, Philadephia, PAMechanical obstruction of odorant flow to olfactory receptor sites islikely one of the primary causes of olfactory loss in chronicrhinosinusitis (CRS) patients, in addition to other possible pathologicalmechanisms. However, quantifying the functional impact of variousnasal obstructions and the subsequent treatment outcomes usingacoustic rhinometry (AR), rhinomanometry (RM) or CT scans isuninformative: numerous studies have shown a poor correlationbetween conventional measurements and patients´ subjective symptomsor measures of psychophysical performance. In this preliminary study,8 CRS patients were assessed using AR, RM and CT scans, and theirodor identification and olfactory thresholds (to carvone, d-limonene andphenethyl alcohol) were also obtained. Using computational fluiddynamics techniques, we converted each patient´s CT scans into ananatomically accurate 3-D numerical nasal model that was used tosimulate nasal airflow and predict odorant delivery rates to the olfactoryepithelium. The accuracy of the models were verified by comparingmodel predictions with measured nasal resistance, airflow rates,pressure drops, area-distance function, etc. Variations in measuredolfactory sensitivity were then correlated with differences of nasalairflow and odorant delivery rates to olfactory neuroepithelium. Ourultimate goal is to quantitatively reveal the underlying conductivemechanisms contributing to olfactory loss in CRS that cannot bedetermined using the existing tools. In the future, such modelingtechniques may provide quantitative evaluation of treatment for CRSand an important pre-treatment guide to optimize airflow and odorantdelivery in human nose. NIH P50 DC006760378 Symposium Presidential: Why Have Neurogenesis inAdult Olfactory Systems?ADULT NEUROGENESIS IN THE MAMMALIAN BRAINGould E. 1 1 Psychology, Princeton University, Princeton, NJThe hippocampus undergoes substantial neurogenesis in adulthood—in the young adult rat many thousands of new neurons are producedeveryday. Adult neurogenesis in the hippocampus has been observed inmany mammalian species, including humans. The formation of newneurons in this brain region is affected by hormones and experience.Numerous forms of stress, including exposure to predator odor, havebeen shown to exert a negative influence on cell proliferation in thehippocampus. On the other hand, enriched environments, learning andphysical activity have a positive effect on the number of new neurons.These findings suggest potential roles for adult neurogenesis. Since thehippocampus is important for certain types of learning and memory, aswell as for anxiety and stress regulation, new neurons may participate inthese functions.379 Symposium Presidential: Why Have Neurogenesis inAdult Olfactory Systems?THE OLFACTORY PATHWAY OF DECAPOD CRUSTACEANS—A MODEL FOR LIFE-LONG NEUROGENESISSchmidt M. 1 1 Biology, Georgia State University, Atlanta, GADecapod crustaceans are similar to vertebrates in having life-longneurogenesis in both the peripheral and central olfactory pathways.Work from various labs over the last decade has revealed that incrustaceans adult neurogenesis in the olfactory organ occurs as a slow“longitudinal” turnover and net addition of receptor units whereas in thecentral olfactory pathway it mainly consists of a slow, continuousaddition of neurons. Compared to the situation in the vertebrateolfactory bulb, adult neurogenesis in the central olfactory pathway ofcrustaceans shows similarities but also distinct differences. Mostnotable among the similar features is the susceptibility of crustaceanadult neurogenesis to a host of external and internal parameters, such asafferent input, serotonin level, season of the year, environmentalrichness, and social status. In contrast to the vertebrate situation, thepredominant neuron type produced in adult crustacean brains areprojection neurons, while new local interneurons are generated in lowernumber and only in some species. Furthermore, recent studies indicatethat in crustaceans very few neuroblasts serve as neuronal stem cellswhereas in the vertebrate olfactory bulb new neurons originate frommore numerous astroglia-like precursors. Further analysis of adultneurogenesis in decapod crustaceans will reveal more about itsunderlying cellular mechanisms and its functions in olfactoryinformation processing. Comparing these data with the situation invertebrates might ease identification of fundamental principles in thelayout of the olfactory pathway that are served by and thus require adultneurogenesis.380 Symposium Presidential: Why Have Neurogenesis inAdult Olfactory Systems?SENSORY ENRICHMENT, NEUROGENESIS ANDOLFACTORY LEARNING IN AN ADULT INSECTCayre M. 1 1 Centre National de la Recherche Scientifique, MarseilleCedex9, FranceIn the adult cricket brain, new neurons are being produced throughoutthe insect´s life. This neurogenesis occurs in the main integrativecenters of the insect brain, the mushroom bodies (MB), where theneuroblasts responsible for their formation persist after the imaginalmoult. The rate of production of new neurons is controlled not only byinternal cues such as morphogenetic hormones (juvenile hormone andecdysone) but also by environmental cues. Crickets reared in a sensoryenriched environment presented an increase in neuroblast proliferationas compared to crickets reared in an impoverished environment.Conversely, unilateral sensory deprivation led to reduced neurogenesisin the mushroom body ipsilateral to the lesion. In search of a functionalrole for the new cells, we specifically destroyed mushroom bodyneuroblasts in young adults by gamma-ray irradiation of the head. Wedeveloped a learning paradigm adapted to the cricket, that we called"escape paradigm." Using this operant associative learning test, weshowed that crickets lacking neurogenesis exhibited delayed learningand reduced memory retention of the task, especially when olfactorycues were used. Our results suggest that environmental cues are able toinfluence adult neurogenesis and that in turn, newly generated neuronsparticipate to olfactory integration, optimizing learning abilities of theanimal, and thus its adaptation to its environment. However, we have toconsider and discuss that learning in insects cannot always be attributedto new-born brain neurons because in many insect species neurogenesisis completed during preimaginal stages. This work has been financiallysupported by the FYSSEN Foundation.95
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sniffing behavior. Furthermore, we
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165 Poster Multimodal, Chemosensory
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