Coordination of M1 projection neuron subtypes by oscillations

项目总结/摘要 运动行为，如伸手，通常依赖于初级运动皮层（M1）来执行。振荡 M1的活动伴随着运动动作，这些动作与脑电图相关 事件相关性去极化（ERD），即运动开始时低频功率的损失。 人类、猴子和啮齿动物的脑内记录发现，ERD与运动同时发生 M1的伽马振荡。伽马作为治疗靶点越来越受到关注， 它在几种运动障碍中发生改变，并受到经颅刺激的影响。然而，微电路 对M1中γ振荡的性质和作用还没有很好的研究。考虑到大量的专业投射 M1神经元，了解它们如何在正常受试者中通过伽马协调至关重要。在其他皮质 电路，伽玛振荡取决于主细胞（PN）和快速尖峰之间的相互作用 中间神经元（FSI）。在M1中，投射特异性PN亚型与FSI的连接性不同，表明 它们受到伽马射线的不同调节。该项目旨在了解伽马振荡如何在 到达协调M1中的三种主要类型的PN：锥体束、皮质纹状体和皮质丘脑。在 目的1，记录大鼠熟练伸手动作过程中M1区的局部场电位和单位活动。 细胞外锋电位波形特征将用于识别FSI，而PN将根据 逆向刺激将跟踪爪运动学以测量伸展。对于每个PN亚型，我们将 表征对伽马的夹带、与FSI的协调以及达到相关性。目标2剖析电路 潜在的任何投影特定的伽马夹带差异的机制。对于每对PN亚型， 其中一个将选择性表达兴奋性视蛋白Chrome，而另一个将用GFP标记。 在M1脑切片中，将在γ诱导的脑损伤期间从两个群体进行全细胞膜片钳记录。 通过光遗传学斜坡刺激。这将揭示携带视蛋白的群体诱导局部γ， 以及GFP群体对它的敏感程度。电压钳记录将揭示GFP的相对贡献。 EPSC和IPSC对这些节律的影响，进一步阐明了电路机制。最后，目标3评估了 行为的重要性。在到达任务期间， 每种PN亚型将被递送以使它们的尖峰与正在进行的M1 γ同相或异相地偏置。 这对伽马振幅、行为表现和未受刺激的投射PN的影响将如下： 测定总而言之，这些目标提供了M1伽马如何协调 输出微电路，阐明其生理学，并测试其行为相关性。这些洞察力对于 加深我们对M1和运动障碍中振荡活动的理解，并完善未来的治疗方法。

PROJECT SUMMARY/ABSTRACT Motor acts such as reaching often rely upon the primary motor cortex (M1) for their execution. Oscillatory activities in M1 accompany motor actions, with the dominant electroencephalographic correlate of those actions being event-related desynchronization (ERD), a loss of low frequency power during movement onsets. Intracerebral recordings in humans, monkeys, and rodents have found that ERD co-occurs with movement associated gamma oscillations in M1. Gamma has received increased attention as a therapeutic target because it is altered in several movement disorders and affected by transcranial stimulation. However, the microcircuitry and function of gamma oscillations in M1 are not well studied. Given the abundance of specialized projection neurons in M1, it is crucial to understand how they are coordinated by gamma in normal subjects. In other cortical circuits, gamma oscillations depend on the interaction between principal cells (PNs) and fast-spiking interneurons (FSIs). In M1, projection-specific PN subtypes differ in their connectivity with FSIs, suggesting that they are differentially regulated by gamma. This project seeks to understand how gamma oscillations during reaching orchestrate three major classes of PNs in M1: pyramidal tract, corticostriatal, and corticothalamic. In Aim 1, local field potentials and single unit activity in M1 are recorded during a skilled reaching task in rats. Extracellular spike waveform characteristics will be used to identify FSIs, while PNs will be classified with antidromic stimulation. Paw kinematics will be tracked to measure reaching. For each PN subtype, we will characterize entrainment to gamma, coordination with FSIs, and reaching correlates. Aim 2 dissects the circuit mechanisms underlying any projection-specific differences in gamma entrainment. For each pair of PN subtypes, one will be made to selectively express the excitatory opsin ChroME, while the other will be labeled with GFP. In M1 brain slices, whole-cell patch clamp recordings will be made from both populations during gamma induced by optogenetic ramp stimuli. This will reveal the ability for the opsin-bearing population to induce local gamma, and how sensitive the GFP population is to it. Voltage clamp recordings will reveal the relative contributions of EPSCs and IPSCs to these rhythms, further illuminating circuit mechanisms. Lastly, Aim 3 assesses the behavioral importance of gamma entrainment. During the reaching task closed-loop optogenetic modulation of each of the PN subtypes will be delivered to bias their spiking either in- or out-of-phase with ongoing M1 gamma. The effect this has on gamma amplitude, behavioral performance, and the unstimulated projection PNs, will be determined. Altogether, these aims offer a comprehensive characterization of how M1 gamma coordinates the output microcircuitry, clarifies its physiology, and tests its behavioral relevance. Those insights are necessary for deepening our understanding of oscillatory activities in M1 and motor disordes, and perfecting future therapies.