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

皮质场电位的测量广泛应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，由于缺乏剖析不同种类的细胞如何产生场电位信号的技术，对场电位的神经起源仍然知之甚少。为了克服这个长期存在的障碍，我们的项目应用荧光电压指示器和光学电压成像仪器，这是我们的团队早些时候在NIH BRAIN倡议中创建的。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态的细胞类型特异性记录，我们将在一系列不同的转基因小鼠品系中表达红色和绿色基因编码的电压指示器，每一种都允许在新皮层的锥体神经元或中间神经元类别中选择性表达基因。在光学记录的同时，我们将对皮质lfp进行传统的电记录。这些联合光学和电学测量将是此类测量的首次，并将对每种神经元类型如何影响自发和刺激诱发的皮层场电位活动产生重要见解。在我们收集的小鼠系中，我们将进行3种新型的记录，每种记录都使用尖端仪器，在清醒行为的小鼠中同时对多达2种细胞类型进行光学电压成像：a)光纤电压传感，用于跟踪基因定义的神经种群的电压动态；b)宽视场电压成像的电压振荡和波在特定细胞类型的皮层；c)高速（1khz）光学电压成像的尖峰动态在多达2个神经元类型一次。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，我们将沉默每一种单独的神经元类型，并观察从皮层回路中有效去除这种细胞类型如何影响LFP活性和其他神经元类型的种群电压动态。总之，这些开创性的研究将通过提供不同细胞类型如何形成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。为了确保我们的实验能以最佳方式推进该领域的概念理解，我们的团队包括两名计算神经科学家，他们的专长是对皮质场电位的生物物理学建模。为了促进透明度和开放科学，我们将把所有来自实验的广泛数据集和分析存放在公共存储库中。

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.