Olfactory Glomeruli: Cellular and Network Mechanisms

描述（申请者提供）：肾小球是嗅觉通路中突触整合的初始位点。来自嗅觉受体神经元的轴突表达相同的气味受体投射到嗅球内相同的一个或几个肾小球，在那里它们与二尖瓣/簇状（MT）细胞的树突和肾小球中间神经元突触。气味由肾小球活动的静态模式（“图”）表示。气味是通过嗅来取样的。这对嗅觉肾小球的输入模式施加了强大的时间结构。因此，除了空间组织外，输入肾小球的ON的时间结构还包含气味信息。输往肾小球的ON在时间上的不同模式塑造了嗅觉信息的突触后加工。肾小球的输入模式被转换成输出信号到嗅觉皮层。这种输入输出功能是由OB抑制回路形成的。我们将测试OB抑制回路的操作包含空间和时间信息来塑造OB输出的假设。我们已经确定了肾小球层中四个不同的抑制网络。其中两种是肾小球内的，作用于单个肾小球的水平。另一种是肾小球间回路，它将100个肾小球连接在一个回路中，该回路使用侧抑制来增强MT细胞输入水平的对比。一种新的多肾小球回路连接了数量较少的邻近肾小球（模块？），这些小球可能对结构相似的气味有反应。ET细胞将ON输入连接到所有这些抑制回路。ET细胞本质上在嗅探频率范围内爆发，并被重复的ON输入所携带。因此，它们非常适合赋予肾小球抑制回路以动态特性来编码嗅觉输入的时间结构。本研究探讨了OB抑制回路的静态和动态特性。目的1验证ET细胞破裂放大突触输入的假说。目的2阐明一个新的多肾小球回路的组织、功能和活性依赖性。目的3验证肾小球内和肾小球间回路是动态调节的假设。目的4：探讨浓度和嗅探对气味肾小球编码的作用。嗅觉是通过嗅来感知气味的，但人们对嗅在神经网络水平上如何影响嗅觉编码知之甚少。本研究促进了我们对主动感知在气味感知中的作用的认识。；这项研究可能表明，习得的嗅探策略可能会弥补患病或老年人群气味敏感性的降低。

DESCRIPTION (provided by applicant): 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.