Odor Coding in Piriform Cortex

辨别气味的能力对于躲避捕食者、获取食物或寻找配偶至关重要。协调一致的 梨状皮质(Apcx)中分布的神经元群的活动被认为是直接导致这种形成的原因。 然而，用于表示气味刺激的不同特征的编码策略，例如 气味识别和气味强度，仍然知之甚少。APCX由不同种类的种群组成 神经元可能在形成气味表征和/或将该信息传达给 下游目标区域。人们对它们的实际作用知之甚少，因为大多数对皮质气味的调查 编码与细胞类型或靶点投射无关。此外，以前的大多数研究都是在 麻醉的动物，其中细胞的功能和随之而来的皮质表现可能是DRA-R。 被人为地改变了。这里的目的是了解气味刺激的不同特征是如何表示的 在不同的APCx神经元群体中表达，并阐明了潜在的神经回路机制 塑造这些表示法。使用的方法将是在大型的整体中记录气味诱发的尖峰 清醒小鼠的APCx神经元的功能鉴定。中心假设是独立的编码策略- GES被用来代表气味识别和气味强度，不同类型的APCX细胞发挥着不同的作用 在塑造这些表现形式方面的作用。这些研究的基本原理是，确定气味是如何表示的 在清醒的动物身上发出信号，行为举止对了解嗅觉系统的功能至关重要。对这件事 目标1：确定梨状皮质如何同时反应。 憎恨气味识别和气味强度。初步研究表明气味识别编码在Distrib- APCx神经元的集合，并且这些集合在很大程度上是浓度不变的(即，空间等同)。 Tity代码)；并且气味强度通过集合活动的同步性(即，时间强度)来编码 代码)。目的2：确定不同亚型的APCx神经元的气味反应，这是由遗传学定义的。 通过层状组织或通过不同的投射目标。体内光遗传标记将被用于识别 在确定的神经元亚型中的反应。不同类型神经元的气味反应被预测为 反映他们在塑造整体中的特定角色或与不同的气味刺激最相关的特征 目标区域。目的3：确定循环回路如何塑造皮质气味表征。输出 来自主神经元的信息将被单侧阻断，从而允许同时进行双侧控制和记录 “前馈”电路。初步数据表明，循环回路极大地影响了大小、时间进程和 在APCx中获得气味响应。这一提议具有创新性，因为它采用了新的工具和方法来重新 清醒动物大量神经元的脊髓气味诱发活动，并归因于不同的反应。 与已识别的大脑皮层回路元素有关。这一贡献意义重大，因为它将提供深刻的见解 通过了解潜在的电路机制，了解气味在梨状皮质中是如何表现的。

The ability to identify an odor is crucial for avoiding predators, obtaining food or finding a mate. The concerted activity of distributed ensembles of neurons in piriform cortex (aPCx) is thought to lead directly to the formation of an odor percept however the coding strategies used to represent different features of an odor stimulus, like odor identity and odor intensity, remain poorly understood. aPCx consists of a heterogeneous population of neurons that likely serve distinct roles in shaping odor representations and/or conveying this information to downstream target areas. Little is known about how they actually do so as most investigations into cortical odor coding were agnostic to cell type or target projection. Moreover, most previous studies were performed in anesthetized animals, where both the cells' functions and consequent cortical representations may be dra- matically altered. The objective here is to understand how different features of an odor stimulus are repre- sented in diverse populations of aPCx neurons, and elucidate the underlying neural circuit mechanisms that shape these representations. The approach used will be to record odor-evoked spiking in large ensembles of functionally identified aPCx neurons in awake mice. The central hypothesis is that independent coding strate- gies are used to represent odor identity and odor intensity, and that different types of aPCx cells play distinct roles in shaping these representations. The rationale for these studies is that determining how odors are repre- sented in aPCx of an awake, behaving animal is crucial for understanding olfactory system function. To this end the following three aims are proposed: Aim 1: To determine how piriform cortex simultaneously rep- resents odor identity and odor intensity. Preliminary studies suggest that odor identity is encoded in distrib- uted ensembles of aPCx neurons, and these ensembles are largely concentration-invariant (i.e. a spatial iden- tity code); and odor intensity is encoded by the synchrony of the ensembles activity (i.e. a temporal intensity code). Aim 2: To determine odor responses in diverse subtypes of aPCx neurons, defined genetically, by laminar organization or by distinct projection targets. In vivo optogenetic tagging will be used to identify responses in defined subtypes of neurons. Odor responses in different subtypes of neurons are predicted to reflect their specific roles in shaping the ensemble or the feature of the odor stimulus most relevant for different target regions. Aim 3: To determine how recurrent circuitry shapes cortical odor representations. Output from principal neurons will be unilaterally blocked, permitting simultaneous bilateral recordings of control and “feedforward” circuits. Preliminary data suggest recurrent circuits dramatically shape the size, timecourse and gain of odor responses in aPCx. This proposal is innovative because it deploys novel tools and methods to re- cord odor-evoked activity in large populations of neurons in awake animals and ascribe distinct response prop- erties to identified cortical circuit elements. This contribution is significant because it will provide deep insight into how odors are represented in piriform cortex through understanding underlying circuit mechanisms.