Dissecting neocortical field potential dynamics using optical voltage imaging in genetically targeted cell-types

皮质场电位的测量广泛用于基础和临床神经科学，包括脑电图（EEG）、皮质电图（ECoG）和局部场电位（LFP）记录。然而，场电位的神经起源仍然知之甚少，由于缺乏解剖技术如何不同类别的细胞有助于场电位信号。为了克服这一长期存在的障碍，我们的项目将荧光电压指示器和仪器应用于我们的团队在NIH BRAIN Initiative早期创建的光学电压成像。这些新工具将使我们能够系统地识别12种不同细胞类型对新皮层场电位活动的贡献。 为了进行神经跨膜电压动力学的细胞类型特异性记录，我们将在广泛的一组不同的转基因小鼠系中表达红色和绿色遗传编码的电压指示剂，其中每一个都允许在新皮层的锥体神经元或中间神经元类中的一个中选择性基因表达。在光学记录的同时，我们将进行传统的皮层LFPs的电记录。这些联合光学和电学测量将是第一次，并将产生重要的见解，每个神经元类型如何影响自发和刺激诱发的皮层场电位活动。 在我们收集的小鼠品系中，我们将进行3种新型的记录，每种记录都使用尖端仪器在清醒行为小鼠中同时对多达2种细胞类型进行光学电压成像：a）光纤电压传感，用于跟踪遗传定义的神经群体的电压动力学; B）特定细胞类型中跨皮层的电压振荡和波的宽场电压成像; c）一次最多2个神经元类型的尖峰动态的高速（1 kHz）光电压成像。此外，为了测试每个神经元类别在形成皮层场电位中的因果作用，我们还将在每个小鼠品系中进行化学发生抑制研究。在这些研究中，我们将沉默每一个单独的神经元类型，并观察如何从皮层回路中有效地去除这种细胞类型影响LFP活动和其他神经元类别的群体电压动态。 总之，这些突破性的研究将通过提供对不同细胞类型如何塑造场电位动力学的基本见解，推动对基础和应用神经科学中皮层场电位的理解。为了帮助确保我们的实验最佳地推进该领域的概念理解，我们的团队包括2名计算神经科学家，他们的专业知识在于对皮层场电位的生物物理学进行建模。为了促进透明度和开放科学，我们将把实验中所有广泛的数据集和分析存款到公共存储库中。

Measurements of cortical field potentials are widely used throughout basic and clinical neuroscience, including in electroencephalography (EEG), electrocorticography (ECoG) and local field potential (LFP) recordings. However, the neural origins of field potentials remain poorly understood, due to a lack of techniques for dissecting how different classes of cells contribute to field potential signals. To overcome this longstanding barrier, our project applies fluorescent voltage-indicators and instrumentation for optical voltage-imaging that our team created earlier in the NIH BRAIN Initiative. These new tools will enable us to systematically identify the contributions of 12 different cell-types to neocortical field potential activity. To perform cell-type specific recordings of neural transmembrane voltage dynamics, we will express red and green genetically encoded voltage indicators in a wide set of different transgenic mouse lines, each of which allows selective gene expression in one of the pyramidal neuron or interneuron classes of the neocortex. Concurrent with optical recordings, we will perform traditional electrical recordings of cortical LFPs. These joint optical and electrical measurements will be the first of their kind and will yield important insights into how each neuron-type influences spontaneous and stimulus-evoked cortical field potential activity. Across our collection of mouse lines, we will conduct 3 novel types of recordings, each of which uses cutting-edge instrumentation for optical voltage-imaging in up to 2 cell-types at once in awake behaving mice: a) Fiber-optic voltage-sensing, for tracking the voltage dynamics of genetically defined neural populations; b) Wide-field voltage-imaging of voltage oscillations and waves across the cortex in specific cell-types; c) High-speed (1 kHz) optical voltage imaging of spiking dynamics in up to 2 neuron-types at a time. Further, to test the causal role of each neuron class in shaping cortical field potentials, we will also perform chemogenetic inhibition studies in each of the mouse lines. In these studies, we will silence each of the individual neuron-types and observe how the effective removal of this cell-type from cortical circuitry impacts both LFP activity and the population voltage dynamics of other neuron classes. Together, these groundbreaking studies will propel understanding of cortical field potentials in basic and applied neuroscience by providing fundamental insights into how different cell-types shape field potential dynamics. To help assure that our experiments optimally advance conceptual understanding in the field, our team includes 2 computational neuroscientists whose expertise lies in modeling the biophysics of cortical field potentials. To promote transparency and open-science, we will deposit all of the extensive datasets and analyses from our experiments into public repositories.