Olfactory Glomeruli: Cellular and Network Mechanisms

描述(申请人提供)：肾小球是嗅觉通路中突触整合的初始位置。表达相同气味感受器的嗅觉感受器神经元的轴突投射到嗅球中相同的一个或几个肾小球，在那里它们与二尖瓣/簇状(MT)细胞和肾小球间神经元的树突突触。气味是由肾小球活动的静态模式(MAP)表示的。气味是通过闻来取样的。这对嗅小球的输入模式施加了很强的时间结构。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。在时间上不同的ON输入模式影响了嗅觉信息的突触后处理。肾小球的输入模式被转换为嗅皮层的输出信号。这种输入输出函数是由OB抑制电路形成的。我们将检验这样的假设，即OB抑制电路的操作结合了空间和时间信息来塑造OB输出。我们在肾小球层发现了四个不同的抑制网络。其中两个是肾小球内，在单个肾小球水平上运行。另一种是肾小球间回路，将肾小球的S连接到一个回路中，该回路利用侧向抑制在MT细胞的输入水平上增强对比度。一种新的多肾小球回路‘墨迹较少的邻近肾小球(模块？)可能对结构相似的气味有反应。ET细胞连接到所有这些抑制电路的输入。ET细胞本质上在嗅探频率范围内爆发，并受到重复输入的影响。因此，它们非常适合于赋予肾小球抑制电路动态特性来编码嗅觉输入的时间结构j。本研究研究OB抑制电路的静态和动态特性。目的1验证ET细胞爆裂放大突触输入的假说。目的2阐明一种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说。目的：研究气味浓度和嗅觉对气味肾小球编码的影响。气味是通过嗅觉来感知的，但人们对嗅觉如何在神经网络层面上影响嗅觉编码知之甚少。本研究加深了我们对主动感觉在气味知觉中的作用的理解。这项研究可能表明，在患病或老年人群中，学习的嗅觉策略可能如何弥补气味敏感度的降低。

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.