Glomeruli are the initial site of synaptic integration in the olfactory pathway. Axons from olfactory receptor neurons expressing the same odorant receptor project to the same one or few glomeruli in the olfactory bulb, where they synapse on the dendrites of mitral/tufted (MT) cells and glomerular interneurons. Odors are rep- resented by static patterns of glomerular activity ('maps'). Odors are sampled by sniffing. This imposes a strong temporal structure on the pattern of input to olfactory glomeruli. Thus, in addition to spatial organization, the temporal structure of ON input to glomeruli contains odor information. Temporally distinct patterns of ON input to glomeruli shape the postsynaptic processing of olfactory information. Patterns of glomerular in- put are transformed into output signals to olfactory cortex. This input-output function is shaped by OB inhibitory circuits. We will test the hypothesis that the operations of OB inhibitory circuits incorporate both spatial and temporal information to shape OB output. We have identified four distinct inhibitory networks in the glomerular layer. Two of these are intraglomerular, operating at the level of single glomeruli. Another, the interglomerular circuit, links 100's of glomeruli in a circuit that uses lateral inhibition to enhance contrast at the level of inputs to MT cells. A new multiglomerular circuit' inks smaller numbers neighboring glomeruli (modules?) that may be responsive to structurally similar odors. ET cells link ON inputs to all these inhibitory circuits. ET cells intrinsically burst in the range of sniffing frequencies and are entrained by repetitive ON input. Thus, they are ideally suited to endow glomerular inhibitory circuits with dynamic characteristics to encode j the temporal structure of olfactory input. This research investigates the static and dynamic properties of OB inhibitory circuits.
Aim 1 Tests the hypothesis that ET cell bursting amplifies synaptic input.
Aim 2 Elucidates the organization, function and activity-dependence of a new multiglomerular circuit.
Aim 3 Tests the hypothesis that intra- and inter-glomerular circuits are dynamically regulated.
Aim 4 : Investigate the roles of concentration and sniffing to odor glomerular coding. Odors are sensed by sniffing but little is known about, how sniffing influences olfactory coding at the neural network level. The present research advances our understanding the role of active sensing in odor perception. ;The research may indicate how learned sniffing strategies might compensate for reduced odor sensitivity in diseased or aged populations. ? ? ?

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
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Somatosensory and Chemosensory Systems Study Section (SCS)
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Davis, Barry
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University of Maryland Baltimore
Anatomy/Cell Biology
Schools of Medicine
United States
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Zhou, Fu-Wen; Puche, Adam C; Shipley, Michael T (2018) Short-Term Plasticity at Olfactory Cortex to Granule Cell Synapses Requires CaV2.1 Activation. Front Cell Neurosci 12:387
Liu, Shaolin; Puche, Adam C; Shipley, Michael T (2016) The Interglomerular Circuit Potently Inhibits Olfactory Bulb Output Neurons by Both Direct and Indirect Pathways. J Neurosci 36:9604-17
Cockerham, Renee; Liu, Shaolin; Cachope, Roger et al. (2016) Subsecond Regulation of Synaptically Released Dopamine by COMT in the Olfactory Bulb. J Neurosci 36:7779-85
Brill, Julia; Shao, Zuoyi; Puche, Adam C et al. (2016) Serotonin increases synaptic activity in olfactory bulb glomeruli. J Neurophysiol 115:1208-19
Brunert, Daniela; Tsuno, Yusuke; Rothermel, Markus et al. (2016) Cell-Type-Specific Modulation of Sensory Responses in Olfactory Bulb Circuits by Serotonergic Projections from the Raphe Nuclei. J Neurosci 36:6820-35
Carey, Ryan M; Sherwood, William Erik; Shipley, Michael T et al. (2015) Role of intraglomerular circuits in shaping temporally structured responses to naturalistic inhalation-driven sensory input to the olfactory bulb. J Neurophysiol 113:3112-29
Liu, Shaolin; Shao, Zuoyi; Puche, Adam et al. (2015) Muscarinic receptors modulate dendrodendritic inhibitory synapses to sculpt glomerular output. J Neurosci 35:5680-92
Rothermel, Markus; Carey, Ryan M; Puche, Adam et al. (2014) Cholinergic inputs from Basal forebrain add an excitatory bias to odor coding in the olfactory bulb. J Neurosci 34:4654-64
Shao, Zuoyi; Puche, Adam C; Shipley, Michael T (2013) Intraglomerular inhibition maintains mitral cell response contrast across input frequencies. J Neurophysiol 110:2185-91
Liu, Shaolin; Plachez, Celine; Shao, Zuoyi et al. (2013) Olfactory bulb short axon cell release of GABA and dopamine produces a temporally biphasic inhibition-excitation response in external tufted cells. J Neurosci 33:2916-26

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