Sniffing and optical imaging of olfactory bulb responses

描述（由申请人提供）：该项目的目标是了解在清醒的大鼠嗅探过程中，嗅觉受体神经元在其输入嗅球水平上的气味表征是如何被修改的。虽然嗅球的群体反应和嗅闻行为已经在一定程度上进行了分离探索，并且已经清楚嗅闻可能对气味编码产生重大影响，但嗅闻如何影响嗅觉系统中的气味编码仍然是完全未知的。气味信息从空间组织大致的嗅上皮到空间组织高度有序的嗅球的转化，是这个编码过程的关键步骤，这是由嗅觉受体神经元高度特异性地收敛到肾小球所允许的。很明显，气流可以调节气味吸收到嗅觉上皮的位置，并且很明显，受体神经元的空间组织绝不是随机的。嗅球的输入就像嗅觉感受器的窗口，因此很可能受到嗅探的影响。如果是这样，这无疑也会对高阶处理产生重大影响。事实上，有几个重要的假设都是基于嗅探是不变的这一假设。本研究将通过在大鼠执行嗅觉辨别任务和测量嗅觉活动时，对嗅觉受体神经元末梢的活动进行选择性成像，重点研究嗅闻气味对嗅觉通路第一层次气味信息编码和处理的影响。具体来说，本研究将：1)确定嗅探在多大程度上调节嗅球中的神经气味图；2)确定对较低气味浓度的增强嗅探现象是否会导致输入到球茎的气味映射的浓度不变。总之，这些实验将在理解嗅觉通路的特定水平上的气味质量编码如何受到大鼠普遍存在的自然嗅探行为的影响方面迈出重要的一步。了解嗅觉系统的基本功能可以潜在地改善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.