1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

277 Poster Central Olfaction and Chemical EcologyTEMPORAL CODING OF SIMILAR TASTANTS IN THENUCLEUS OF THE SOLITARY TRACT OF THE RATRoussin A.T. 1 , Di Lorenzo P.M. 1 , Victor J.D. 2 1 Psychology, StateUniversity of New York at Binghamton, Binghamton, NY; 2 Neurologyand Neuroscience, Weill Medical College of Cornell University, NewYork, NYRecent work has shown that spike timing in the first 2 s of responsein the nucleus of the solitary tract (NTS) contributes to coding of tastequality. Cells with especially variable response magnitudes acrossrepeated stimulus presentations typically showed the greatest evidenceof temporal coding. Responses to repeated trials of tastants that were ofsimilar quality (salty, sour, sweet or bitter) but were of differentchemical composition were recorded in the NTS of anesthetized rats.Stimuli were NaCl (0.1 M), LiCl (0.1 M), HCl (0.01 M), citric acid(0.01 M), sucrose (0.5 M), fructose (0.3 M), quinineHCl (0.01 M) andurea (1.0 M). Temporal coding was assessed using an informationtheoreticapproach (Victor & Purpura, 1996). Response magnitudesevoked by similar-tasting stimuli varied substantially, and oftenindependently from each other, across trials. Spike timing contributed tothe information present in taste responses when the relative magnitudesof response to different tastants varied across trials whether the tasteresponses were evoked by similar or dissimilar tastants. Conversely,when the response to one stimulus of a pair was always greater than theother, rate coding was more likely to account for the informationconveyed by the responses. These data suggest that spike timing maycontribute to discrimination between tastants in cases where firing ratealone is not sufficient, regardless of whether those tastants evoke thesame quality. Supported by NIDCD RO1-DC005219 and NIMH R01-MH68012 to D. Gardner.278 Poster Central Olfaction and Chemical EcologyFUNCTIONAL CHARACTERIZATION OF LOBSTEROLFACTORY PROJECTION NEURONSAggio J.F. 1 , Ache B.W. 1 1 The Whitney Laboratory for MarineBioscience, University of Florida, St. Augustine, FLSome larger crustaceans have a unique neuropil associated with theolfactory lobe (OL) called the accessory lobe (AL). The AL receivesolfactory input from a distinct subset of local interneurons arborizing inthe sub-cap region of OL glomeruli, although the role of the AL inprocessing olfactory information is unknown. Using a perfused nosebrainpreparation, we characterized the responses of OL and ALprojection neurons (PNs) to olfactory (antennular) input. In contrast tothe largely silent OL PNs, AL PNs exhibit spontaneous bursts of actionpotentials (APs) with a period of 12.3 ± 1.3 s (n = 6). Ablation ofantennular chemoreceptors abolishes the spontaneous bursting.Odorants evoke APs in both OL and AL PNs in an odorant- andconcentration-dependent manner. OL PNs respond with a complex,often multiphasic train of APs. AL PNs respond with a single phasictonictrain of APs, the duration and latency of which is phase-dependenton the ongoing bursting activity of the cells. AL PNs also respond tovisual stimuli with a shorter latency than to odorants (327 ± 48 ms [n =37] vs 777 ± 171 ms, [n = 12]). The ON response to light shortens thesubsequent response to odorant, which in turn abolishes the OFFresponse to light. Our findings raise the interesting possibility that ALPNs are multimodal neurons that process input from a recentlydiscovered subset of inherently oscillatory olfactory receptor neuronsthat may terminate in the sub-cap region of OL glomeruli.279 Poster Central Olfaction and Chemical EcologyA COMPARISON OF ENSEMBLE REPRESENTATIONS FORNATURAL PLANT-ODOR BLENDS AND BLENDCOMPONENTS IN THE ANTENNAL LOBE OF THE MOTHMANDUCA SEXTARiffell J.A. 1 , Christensen T.C. 1 , Hildebrand J.G. 1 1 Division ofNeurobiology, University of Arizona, Tucson, AZAlthough most organisms in nature operate at low odor intensities,many chemosensory studies use olfactory stimuli at non-physiologicalconcentrations. Moreover, clear understanding of how the brainprocesses complex mixtures as opposed to single odorants has provenelusive owing to the lack of adequate analytical methods. Using themoth, Manduca sexta, we first approached an improved understandingof the behavioral importance of complex blends through wind-tunnelexperiments to odors from hostplant flowers. Selective removal of keyblend components suppressed upwind flight responses in comparison tothe entire blend. To compare how the antennal lobe (AL) of M. sextaencodes behaviorally relevant floral mixtures and single constituents, amulti-channel neural-ensemble recording array was coupled with aGCMS. Integration of these two technologies allows examination of ALresponse to natural complex mixtures and provides a means offractionating those same blends into their single components.Approximately 25% of the units responded specifically to singleodorants. Moreover, odor-evoked activity was often spatially restrictedto distinct regions of the AL. Spatiotemporal ensemble dynamics wereclearly modulated differentially by the blend as compared to the singleodorants alone. Together, these results provide new evidence that inmoths, upwind orientation to blends is mediated by the preciseintegration of multiple glomerular pathways, and that blend inputtransforms the network representations in a manner that is not predictedfrom responses to single odor compounds. Supported by NIH grantsDC-02751 and 2 K12 GM000708-06.280 Poster Central Olfaction and Chemical EcologySPATIAL AND TEMPORAL ORGANIZATION OF ODORREPRESENTATION BY UNIGLOMERULAR PROJECTIONNEURONS IN THE MOTH ANTENNAL LOBENamiki S. 1 , Kanzaki R. 2 1 Graduate School of Life and EnvironmentalSciences, University of Tsukuba, Tsukuba, Ibaraki, Japan; 2 Mechano-Informatics, Graduate School of Information Science and Technology,University of Tokyo, Bunkyo-ku, Tokyo, JapanThe antennal lobe (AL) is the first relay station for olfactoryinformation in the insect brain and the anatomical equivalent of theolfactory bulb (OB) of mammals. Both systems have commonstructures called glomeruli in which neurons make synapses. Olfactoryreceptor neurons expressing the same receptor project to the sameglomeruli in the AL. Projection neurons (PNs), the AL output neurons,transmit the processed information into higher order olfactory centers.To investigate spatial and temporal patterning of glomerular activity, wereconstructed olfactory representation by pooled set of single PNrecordings. Most of PNs innervated single glomeruli (n = 126). PNsshowed various slow temporal patterns to odor. PNs innervating thesame glomerulus had similar response profiles so that we couldreconstruct odor-evoked spatial pattern of PNs firing in the AL. Thisreconstructed spatial map is highly distributed and dynamic. Differentodor elicited different spatial pattern at each time point. The Euclidiandistances between odor representations reached maximum at 200 msafter the response onset. There were no clear correlation betweenphysical distance of glomeruli and response similarity of odor-evokedslow temporal patterns. This result is consistent with prior calciumimaging and modeling study. We conclude that olfactory information isencoded by distributed spatial and temporal pattern of PNs firing andthere are no clear relationship between the physical distance andresponse pattern in the moth AL.70