2009 Abstracts - Association for Chemoreception Sciences

#15 Gender effects on olfactory processingNeural control of sexually dimorphic behaviorsNirao ShahUCSF San Franciscio, CA, USASex specific behaviors such as mating and aggression are innatebehaviors in mice as they can be displayed without prior trainingor experience. Nevertheless, these behaviors are tightly regulatedby pheromones as well as by sex steroid hormones. We willpresent data demonstrating distinct sensory and hormonalcontrol of these behaviors.#16 Presidential Symposium: On beyond glomeruliFunctional Architecture of Inhibition in the Olfactory Bulb:Glomeruli and BeyondMichael T ShipleyDepartment of Anatomy & Neurobiology, Program inNeuroscience University of Maryland School of MedicineBaltimore, MD, USASensory inputs are transformed to outputs via mitral and tufted(MT) cell projections to olfactory cortex (POC). Inhibitionshapes this transformation at two levels: Glomerular circuitsmediate presynaptic inhibition of olfactory nerve (ON) terminalsand postsynaptic inhibition of MT apical dendrites.Infraglomerular circuits exert postsynaptic inhibition at MTlateral dendrites. Glomerular circuits: Two intraglomerularglomerular circuits operate on single glomeruli to mediatetonic/phasic and pre-/postsynaptic inhibition. Interglomerularcircuits enhance contrast among hundreds of distant glomeruliand multiglomerular circuits link smaller groups of neighboringglomeruli roughly the size of ‘modules’ responsive to structurallysimilar odors. Glomerular circuits lack POC feedback butcentrifugal modulatory inputs (5HT, ACh) strongly shapepre- and postsynaptic inhibition. Infraglomerular circuits:MTs reciprocally synapse with granule cells (GC), which mediaterecurrent and lateral inhibition of MTs. Infraglomerular circuitsare targeted by central modulatory inputs (5HT, ACh, NE).They receive massive cortical inputs, which excite GCs thusinhibiting MTs. How do these inhibitory circuits shape olfactoryprocessing? Modulatory inputs provide behavioral statedependent regulation of both glomerular and infraglomerularcircuits. Glomerular circuits are driven by sensory signals. Theyfollow repetitive ON inputs and exert more powerful inhibitionof MTs than previously thought. They temporally sharpen MTfiring and maintain contrast among glomerular outputs acrossdynamic changes in odor concentration. Infraglomerular circuitsare strongly influenced by cortical feedback, which may regulatechanges in MT firing across sniff cycles. Cortical feedback maymediate experience-dependent plasticity.#17 Presidential Symposium: On beyond glomeruliOlfactory systems theoryThomas A. Cleland 1 , Christiane Linster 21Dept. Psychology, Cornell University Ithaca, NY, USA, 2 Dept.Neurobiology & Behavior, Cornell University Ithaca, NY, USAThe idea that glomerular activation patterns underlie odorperception and recognition is analogous to claiming that theinverted image maps of photoreceptor activation identify visualobjects; that is, the statement is not clearly wrong, but missesnearly the entirety of the problem. As with any sensory system,the olfactory receptor neuron layer serves the primary purposeof transducing environmental variance into profiles of neuralactivity. The resulting primary representations are degenerate,occluded, and naïve reflections of the odor environment;nominally identical stimuli emit variable odor signatures,unpredictable mixture elements and background odorsirreversibly interfere with the replicability of receptor activationprofiles, and there exists no clear means to distinguish importantfrom random sources of sensory variance. Meaningful perceptualinformation must be constructed from this pool of structuredvariance by the neural circuitry of the olfactory bulb (OB) and themultiple secondary structures to which it projects. We will outlinethe computational problems faced by the olfactory system anddescribe models for how the architectures of its successive layersof neuronal processing contribute to their resolution. Particularattention will be paid to the analogous problems faced by othersensory systems, as well as the differences between them, and tothe role of memory in olfactory perception. Expanding upon ahistory of comparing the OB to the retina, we propose that anamalgam of the retina and primary visual cortex (V1) is a moreappropriate visual-system analogy for OB function.#18 Presidential Symposium: On beyond glomeruliOscillatory Modes and the Role of Task Structure inEarly Olfactory ProcessingLeslie M. KayDepartment of Psychology and Institute for Mind & Biology,The University of Chicago Chicago, IL, USAEarly stages of processing in the olfactory system are oftenconsidered to consist of relatively static mechanisms, dictated byglomerular input patterns, with minor adjustments related tointensity of the input signal and modulation of its strength bycentral processes. More recently, it has been shown by my lab andothers that changes in the temporal precision of mitral cells,signified by the gamma oscillation of the local field potential, arerelated to processing highly overlapping odorant input patterns.Recent work from my laboratory shows that gamma oscillationsare modified dependent on task demands. However, we have alsoshown that the structure of the task used to determine odoridentification can influence the type of oscillatory mode, theinvolvement of central brain areas in primary odor processing,and the difficulty of the discrimination itself. We show thatchanging the task from a two-alternative choice to a go/no-go taskalters the way in which the olfactory bulb, piriform cortex andhippocampus participate in odor processing. The oscillatorysignature changes from a gamma oscillation local to the olfactorybulb, to a beta oscillation that is coherent with activity in theseAbstracts | 11