2009 Abstracts - Association for Chemoreception Sciences

#P115 Poster session III: Cortical chemosensoryprocessing/Receptor genomics and molecular biologyPerceptual Decision-Making in the Human Olfactory BrainNicholas E. Bowman, James D. Howard, Konrad P Kording,Jay A. GottfriedNorthwestern University Chicago, IL, USALittle is known about how percepts of odor quality develop in thecontext of olfactory decision-making. Using functional magneticresonance imaging (fMRI) and psychophysical testing weinvestigated the evolution of odor percepts in the human brainand the role of perceptual decision-making in the disambiguationof odor mixtures. A binary odor-mixture set of citral (lemon) andeugenol (clove) was assembled, systematically varying betweenpure citral and pure eugenol, with a total of nine discretemixtures. Participants were instructed to make as many sniffs asneeded to confidently identify which of the two odors was moreprevalent in a given odor mixture trial. After making this binarydecision, subjects made an analog rating on a continuum betweenpure lemon and pure clove, indicating to what extent theyperceived the two odors contributed to the mixture. Psychometricdata from nine subjects show that analog perceptual decisionsreflected the ratio of the pure odorants, and reaction timesincreased with the ambiguity of the odor. At this time, we havecompleted fMRI data collection and analysis from one subject(additional subjects to be presented). Preliminary findingsrevealed increased activation for less ambiguous odor trials inprimary olfactory (piriform) cortex, whereas an inverse patternwas observed in orbitofrontal cortex (i.e., increased activity formore ambiguous trials). These preliminary findings may reveal thedifferent roles that these regions play during perceptualdisambiguation of complex odors. Further analyses willspecifically explore whether fMRI ensemble patterns in piriformand orbitofrontal cortices can predict participants’ perceptualdecisions on a trial-by-trial basis.#P116 Poster session III: Cortical chemosensoryprocessing/Receptor genomics and molecular biologyA novel chemical-informatics method to decode odorreceptor chemical spaceSean M Boyle 1 , Anandasankar Ray 21IGERT, GGB, University of California Riverside, CA, USA,2Entomology Department, University of California Riverside,CA, USALittle is know about how odor receptors can detect a wide varietyof volatile chemicals with high degrees of specificity andsensitivity. The problem is particularly complex due to theextreme diversity in both odorant structures and in receptortypes. We have designed a novel chemical-informatics method toidentify shared molecular features amongst odorants that mayparticipate in binding to specific receptors. This ability to identifyimportant molecular features of odorants was utilized to create anovel-ligand-discovery-pipeline that addresses one of the majorchallenges in olfaction. Functional assays for identifying ligandsof odor receptors limit testing to hundreds of compounds whichrepresents an extremely small fraction (