1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

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