Odor Coding in Piriform Cortex

对气味的感知和识别使动物能够识别食物来源，躲避捕食者，并找到 当它们在周围导航时，潜在的配偶。这些行为至少需要三个基本成分：(1)区分相似气味的能力，同时允许泛化 气味识别；(2)获取和检索气味关联；以及(3)为显著气味赋值以 引导适当的行为。尽管梨状皮质(PCX)被认为是嗅觉的中枢 以及气味学习和记忆，PCX是否或如何执行这些基本计算仍然存在 未知。我们的长期目标是机械地理解气味信息是如何被处理来驱动 举止得体。本提案的目标是确定PCX在哪里以及如何执行这些任务 三个基本的计算。PCX有两种主要类型的主细胞，半月细胞(SLS)和Y细胞。 锥体细胞(PYRs)，具有不同的形态、突触连接和投射靶点。我们的 中心假设是不同类型的PCX细胞在这些基本计算中扮演着不同和特定的角色。为此，我们提出了以下三个目标。 目的1：揭示多囊卵巢综合征辨别和概括的神经基础。我们要训练老鼠 为了区分两种气味，然后记录识别出的SLS和PYR，因为给小鼠喂食一系列这两种气味的二元混合物。我们的初步数据支持我们的假设 SLS区分和PYR概括了对相似气味的反应。 目的2：揭示获得和提取气味记忆的神经基础。我们不理解气味记忆是如何形成的，或者它们是在哪里以及如何存储和检索的？我们将使用病毒式工具 用不同的转基因小鼠品系选择性地抑制SLS或PYRs的活性 或者在气味记忆任务的检索阶段之前。我们假设需要SLS才能获得- 气味记忆的获取和提取都需要PYR，但不需要气味记忆的提取。 目的3：确定气味识别和价值信息如何出现在内侧前额叶皮质 (Mpfc)。MPFC从PCX接收直接投影，并对气味值进行编码。我们假设那股气味 信息由一个特定的PYR子集(Tbr1神经元)直接从PCX路由到mPFC； Tbr1神经元编码气味识别，但不编码气味价值；气味识别和气味价值的结合 在mPFC中，通过加强PCX Tbr1神经元与其突触后的联系而发生 MPFC的合作伙伴。 这项研究将揭示PCX神经元和电路的不同亚群在加工过程中所扮演的不同角色 气味信息，以指导灵活和适当的行为，并可以提供更全面的洞察如何 信息在整个大脑的规范回路内和跨规范回路进行转换。

The perception and recognition of odors allow animals to identify food sources, avoid predators, and find potential mates as they navigate their surroundings. These behaviors require at least three essential compu-tations: (1) the ability to discriminate between similar odors while simultaneously allowing generalization for odor recognition; (2) acquiring and retrieving odor associations; and (3) assigning value to salient odors to guide appropriate behaviors. Although the piriform (PCx) cortex is thought to be the locus for odor perception and odor learning and memory, whether or how the PCx performs these essential computations remains unknown. Our long-term goal is to mechanistically understand how odor information is processed to drive appropriate behaviors. The objective of this proposal is to identify where and how the PCx performs these three essential computations. The PCx has two major types of principal cells, semilunar cells (SLs) and py- ramidal cells (PYRs), which have distinct morphologies, synaptic connectivity, and projection targets. Our central hypothesis is that different PCx cell types play distinct and specific roles in these essential com-putations. To this end, we propose the following three aims. Aim 1: To reveal the neural substrates of discrimination and generalization in PCx. We will train mice to discriminate between two odorants and then record from identified SLs and PYRs as the mice are pre-sented with a morphing series of binary mixtures of the two. Our preliminary data support our hypothesis that SLs discriminate and PYRs generalize responses to similar odors. Aim 2: To reveal the neural substrates for acquiring and retrieving odor memories. We do not under-stand how odor memories are formed, or where and how are they stored and retrieved? We will use viral tools with different transgenic mouse lines to selectively suppress activity in SLs or PYRs just before the acquisition or before the retrieval phases of an odor memory task. We hypothesize that SLs are required for the acquisi- tion but not the retrieval of odor memories, while PYRs are required for both acquisition and retrieval. Aim 3: To determine how odor identity and value information emerge in the medial prefrontal cortex (mPFC). mPFC receives direct projections from PCx and encodes odor value. We hypothesize that odor information is directly routed from PCx to mPFC by one specific subset of PYRs (Tbr1 neurons); that Tbr1 neurons encode odor identify but not odor value; and that the conjunction of odor identity and odorvalue in mPFC occurs through strengthening connections between PCx Tbr1 neurons and their postsynaptic partners in mPFC. This study will reveal the distinct roles that different subsets of PCx neurons and circuits play in processing odor information to guide flexible and appropriate behaviors, and can provide more general insight into how information is transformed within and across canonical circuits throughout the brain.