1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

93 Poster Chemosensory Coding and ClinicalOLFACTORY EVENT-RELATED FUNCTIONAL MAGNETICRESONANCE IMAGING STUDY IN YOUNG ADULTSNi D. 1 , Liu J. 2 1 Peking Union Medical College Hospital, Beijing,China; 2 Dept.of Otolaryngology, Peking Union Medical CollegeHospital, Beijing, ChinaObjectives: to explore brain activation mapping following odorpresentation with event-related functional magnetic resonance imaging.Methods: experiments were performed on 10 healthy young volunteersaged from 18 to 28 (5 men and 5 women). Odorant isoamyl acetate wasdelivered by olfactometer synchronously with inspiration birhinally for10 times with interstimulus interval 60 seconds. fMRI method based onthe blood-oxygen-level dependent effect were carried out on a 3.0 Tscanner, using gradient-echo EPI technique. Results: Bilateralactivations of the orbitofrontal cortex, anterior cingulated cortex,piriform cortex, insular cortex, amygdala, thalamus, the basal nuclei,temple cortex, frontal cortex seen. A greater extent of activation wasevident in the right frontal cortex and left orbitofrontal cortex.Conclusions: Olfactory event-related fMRI is an objective measurementof olfaction, and has potential clinical significance.94 Poster Chemosensory Coding and ClinicalHEDONIC-SPECIFIC TEMPORAL PATTERN OF RESPONSEIN PRIMARY OLFACTORY CORTEX OF HUMANSZelano C. 1 , Khan R. 2 , Sobel N. 2 1 Biophysics, University of California,Berkeley, Berkeley, CA; 2 Neuroscience, University of California,Berkeley, CAEvidence suggests that the primary perceptual axis of odor is valence,or how pleasant or unpleasant an odor is. Although human imagingstudies have consistently found that this primary perceptual axis isreflected in orbitofrontal cortex (secondary olfactory cortex), it is notknown whether or how it is reflected in primary olfactory cortex. Weset out to probe this Using fMRI. Subjects were presented with twopleasant odorants (strawberry and citral) and two unpleasant odorants(hydrogensulfide and propionic acid). Odorants were chosen such thatthe pleasant and unpleasant groups contained trigeminal and nontrigeminalodorants. In data from a single subject, we find thattrigeminal odorants elicited significantly lower amplitude BOLDresponse. We also found that unpleasant odorants had significantlygreater full-width-at-half-height, and therefore a much lower slope. Thisresult implies that the hedonic value of odors might be temporallyencoded at the level of primary olfactory cortex. Funding: cz funded byNSFGRFP95 Poster Chemosensory Coding and ClinicalTHE ASSOCIATION BETWEEN OLFACTORY RECOGNITIONMEMORY PERFORMANCE AND BRAIN ACTIVATION INOLDER MALES AND FEMALES: AN FMRI STUDYWang M. 1 , Cerf-Ducastel B. 1 , Pirogovsky E. 1 , Sundermann E. 1 , RattnerK. 1 , Allmon T. 1 , Miller M. 1 , Hackbarth J. 1 , Murphy C. 2 1 San DiegoState University, San Diego, CA; 2 San Diego State University andUCSD Medical School, San Diego, CAThe present study investigated associations between olfactoryrecognition memory performance during fMRI scanning sessions andbrain activation among healthy older adults (10 males, 10 females).Each subject was presented 16 odors immediately prior to entering thescanner. During two functional runs at 3T, target and foil names ofodors were presented and each subject responded via button boxwhether or not each name corresponded with an odor presented to them.Older females demonstrated significantly higher performance on thediscriminability index (d´) than older males, consonant with a higherfalse positive rate of males during functional run 1. The d´ for femaleswas negatively correlated with activation in left parahippocampal gyrusand superior frontal gyrus and positively correlated with bilateralactivation in fusiform gyrus. The d´ for males was positively correlatedwith activation in left parahippocampal gyrus and negatively correlatedwith activation in right superior frontal gyrus. The false positive rate ofmales was positively correlated with activation in bilateral superiorfrontal gyrus and right parahippocampal gyrus and was negativelycorrelated with right medial frontal gyrus. For females, there were nosignificant correlations between false positive rate and brain activation.This study suggests greater impairment in odor recognition memory inolder males that is associated with patterns of cortical activity in frontaland temporal areas. Supported by NIH grant #AG04085 to CM.96 Poster Chemosensory Coding and ClinicalOLFACTORY PERCEPTUAL LEARNING IN HUMANPIRIFORM AND ORBITOFRONTAL CORTEXGottfried J.A. 1 , Li W. 1 , Luxenberg E. 2 , Howard J. 1 1 Neurology,Northwestern University, Chicago, IL; 2 Linguistics, Duke University,Durham, NCEnhancement in sensory acuity as a result of experience is known asperceptual learning. In humans olfactory perceptual learning is criticalto the development of odor discrimination and identification, but theunderlying neural correlates remain poorly defined. Using a crosshabituationparadigm and functional magnetic resonance imaging, weexamined the neural substrates in human piriform and orbitofrontalcortex (OFC) for perceptual learning to odorants qualitatively (QR) orstructurally (SR) related to an odorant destined for habituation (TG). 16subjects smelled TG, QR, SR odorants, and an unrelated control odorant(CT), before and after 3.5-min continuous exposure to TG. Behavioraland neural markers of habituation to the TG odorant were observed inthe form of reduced intensity ratings and progressive signal decline inpiriform cortex. Perceptual learning, indexed as a decrease in similarityratings from pre- to post-habituation, was evident for the TG/QR andTG/SR pairs, but not for the TG/CT pair. In parallel to these behavioraleffects, we observed increased neural activity (from pre- to posthabituation)in piriform cortex for QR and in OFC for both QR and SR,in comparison to CT. Importantly, the increased activity to QR and SRin OFC significantly predicted the subsequent enhancement of odordiscrimination. The data provide robust evidence for olfactoryperceptual learning in human piriform cortex and OFC. These findingsimply that sensory-specific representations of odor quality or structurein piriform and OFC are flexible and can be rapidly updated by mereperceptual experience. Funding: Northwestern Univ.24