Sniffing and optical imaging of olfactory bulb responses

描述(申请人提供)：这个项目的目标是了解嗅觉感受器神经元群体在它们输入嗅球的水平上如何通过嗅觉在清醒的大鼠身上改变气味表示。虽然嗅球的群体反应和嗅觉行为在一定程度上已经被分离出来，而且嗅觉可能对气味编码产生重大影响已经变得明显，但嗅觉实际上是如何影响嗅觉系统中的气味编码的还完全不清楚。气味信息从空间上粗略组织的嗅觉上皮到空间上高度组织的嗅球，通过高度特异的嗅觉感受器神经元会聚到肾小球，是这一编码过程中的关键步骤。显然，气流可以调节气味吸附到嗅觉上皮细胞的位置，很明显，感受器神经元的空间组织绝不是随机的。因此，嗅球的输入很可能会受到嗅觉的影响，嗅球的作用就像嗅觉感受器气味曲目中的一个窗口。如果是这样的话，这无疑也会对更高阶的处理产生重大影响。事实上，有几个重要的假设依赖于嗅探是不变的这一假设。本研究将通过选择性地成像大鼠在执行嗅觉辨别任务并测量嗅觉活动时嗅觉感受器神经元终末的活动，重点研究嗅觉对嗅觉通路第一水平上关于气味的信息的编码和处理的影响。具体地说，这项研究将：1)确定嗅觉对嗅球神经气味映射的调制程度；2)确定对较低气味浓度反应的增强嗅觉现象是否导致输入气味映射到嗅球的浓度不变。总之，这些实验将是理解嗅觉通路特定水平的气味质量编码如何受到老鼠无处不在的自然嗅觉行为影响的重要一步。了解嗅觉系统的基本功能可能会改进神经系统疾病的诊断和治疗。

DESCRIPTION (provided by applicant): The goal of this project is to understand how odorant representations by populations of olfactory receptor neurons at the level of their input to the olfactory bulb are modified by sniffing in awake rats. While population responses of the olfactory bulb and sniffing behavior have been explored to some degree in separation, and it has become clear that sniffing could have a major impact on odorant encoding, it is entirely unknown how sniffing actually affects odor encoding in the olfactory system. The transformation of odorant information from the spatially roughly organized olfactory epithelium to the spatially highly organized olfactory bulb, allowed by highly specific convergence of olfactory receptor neurons onto glomeruli, is a critical step in this encoding process. It is clear that airflow can modulate where odorants sorb to the olfactory epithelium, and it is clear that the spatial organization of receptor neurons is by no means random. The input of the olfactory bulb, which acts like a window on the olfactory receptor repertoire of odorants, is hence likely to be affected by sniffing. If so, this undoubtedly has major affects on higher order processing as well. Indeed, several important hypotheses rely on the assumption that sniffing is invariable. This study will focus on the impact of sniffing of odorants on the coding and processing of information about odors at this first level of the olfactory pathway by selectively imaging activity in olfactory receptor neuron terminals while rats are performing an olfactory discrimination task and sniffing activity is measured. Specifically, this study will: 1) determine to what extent sniffing modulates the neural odormaps in the olfactory bulb; 2) determine whether the phenomenon of enhanced sniffing in response to lower odorant concentrations leads to concentration-invariance of input odormaps to the bulb. Together, these experiments will constitute a significant step towards understanding how odor quality - encoding at a specific level of the olfactory pathway is affected by the ubiquitous and natural behavior of sniffing in rats. Understanding the basic functions of the olfactory system can potentially lead to improved diagnosis and treatment of diseases of the nervous system.