Chronic imaging of odor-evoked activity in olfactory bulb circuits of awake mice

描述(申请人提供)：嗅觉在我们的生活质量中起着重要的作用。然而，控制大脑中嗅觉信息处理和表示的机制还不是很清楚。在哺乳动物中，嗅球是负责最初处理嗅觉信息的关键大脑区域。我们目前对嗅球功能的大部分了解是基于之前使用体外脑片或麻醉动物急性制剂进行的研究。虽然这些方法提供了宝贵的洞察力，但对清醒、行为正常的动物的气味编码知之甚少。例如，同一动物的气味在很长一段时间内(即几天、几周、几个月)的动态表现是什么，以及在清醒的行为动物中，嗅球中的气味编码是如何受到经验和学习的影响的？为了解决这些问题，我们提出了一种实验策略，使用慢性双光子钙成像来研究清醒小鼠嗅球中的气味诱发活动。具体目标1建议开发一种方法，利用Cre依赖的腺相关病毒系统在主(二尖瓣/簇状)细胞或局部中间神经元中选择性表达遗传编码的钙指示剂GCaMP3。我们假设，这种方法将在大量神经集合中提供动作电位依赖的钙信号的单细胞分辨率，这些神经集合可以在清醒的头部固定的小鼠身上长期成像。特定目的2建议进行成像实验，以确定二尖瓣细胞和中间神经元(颗粒细胞)在清醒和麻醉状态下的气味诱发反应有何不同。我们还将使用清醒动物的慢性成像来确定神经集合中气味诱发活动的模式在几天的重复测试中是稳定的还是动态的。这些实验将对清醒大脑中气味编码的性质提供新的见解。

DESCRIPTION (provided by applicant): The sense of smell plays an important role in our quality of life. However, the mechanisms governing the processing and representation of olfactory information in the brain are not well understood. In mammals, the olfactory bulb is a critical brain region responsible for the initial processing of olfactory information. Much of our current understanding of olfactory bulb function is based on previous studies using in vitro brain slices or acute preparations of anesthetized animals. While these approaches have provided valuable insight, much less is known about odor coding in awake, behaving animals. For example, what are the dynamics of odor representations in the same animal over long time scales (i.e. days, weeks, months) and how is odor coding in the olfactory bulb shaped by experience and learning in awake, behaving animals? To address these questions, we propose an experimental strategy using chronic 2-photon calcium imaging to study odor-evoked activity in the olfactory bulbs of awake mice. Specific Aim 1 proposes the development of an approach for the selective expression of the genetically-encoded calcium indicator GCaMP3 in principal (mitral/tufted) cells or local interneurons using a Cre-dependent, adeno-associated virus system. We hypothesize that this approach will provide single cell resolution of action potential-dependent calcium signals in large populations of neural ensembles that can be imaged chronically in awake, head fixed mice. Specific Aim 2 proposes imaging experiments to determine how odor-evoked responses of mitral cells and interneurons (granule cells) differ between the awake and anesthetized state. We will also use chronic imaging in awake animals to determine whether patterns of odor-evoked activity in neural ensembles are stable or dynamic over days of repeated testing. These experiments will provide new insight into the nature of odor coding in the awake brain.