Dissecting the Fabric of the Cerebral Cortex

大脑皮层容纳我们的心理功能，如感知，认知和行动。尽管在发现单细胞和分子水平过程的特性方面取得了重大进展，但我们仍然不知道皮层在电路水平上如何工作。这个问题的本质在于理解数十亿个神经元如何通过数万亿个连接进行通信，协调它们的活动，从而产生我们的心理能力。 我们还远远不能同时测量所有无数皮层细胞的活动，并组装它们的物理布线图（连接体）。然而，如果存在着支配这种复杂性的基本原则和规则，那么发现这些原则就为理解大脑皮层的功能提供了一个显而易见的策略。事实上，已经假设大脑皮层是由基本信息组成的， 处理模块。近世纪来，解剖学家们已经观察到皮质微结构的显著规律性：来自共同祖细胞的细胞串具有突触连接的倾向，排列成与皮质表面垂直的小圆柱。这些微柱被假设为皮层电路的基本功能单位。如果能够 理解它们的组织原则，理解皮层如何工作的任务将大大简化。发现这些基本模块的功能就像发现基因一样，最终导致了世纪的分子革命。到目前为止，由于技术限制，这些结构无法详细研究。要了解微柱的功能，必须 同时监测其所有组成神经元的活性。我们的目标是克服这些技术挑战，并开发研究整个微腔的体内方法。我们建议开发基于3D随机存取多光子（3D-RAMP）激发的体内显微镜。这环法自行车显微镜将采用一系列声光偏转器在长波长，将产生任何所需的操作 3D扫描路径的帧速率比当前最先进的双光子成像系统快两个数量级。这将允许同时在体内记录跨越所有六个皮质层的整列姐妹细胞的活性。显微镜将采用两个3D-RAMP扫描仪，可以同时记录和光刺激神经活动，以组装功能连接图 的微柱。病毒和遗传学方法将用于在体内识别和标记个体发育微柱。通过合作，他们的连接体将被组装起来。我们计划创建一个数据库的微柱架构的皮层，将包括功能，解剖和个体发育信息的组织微柱跨皮层区域，物种和动物模型的疾病。我们的提议有望解开大脑皮层回路是如何组织起来产生神经元的基本原理。 心理功能如果我们成功了，我们的结果将构成我们对大脑理解的一个巨大飞跃。

The cerebral cortex houses our mental functions like perception, cognition and action. Despite major advances in discovering the properties of single cells and molecular-level processes, we still do not know how the cortex works at the circuit level. The essence of the problem lies in understanding how the billions of neurons communicating through trillions of connections orchestrate their activities to give rise to our mental faculties. We are far from being able to simultaneously measure the activity of all the myriads of cortical cells and assemble their physical wiring diagram (connectome). However, if there are underlying principles and rules that govern this complexity, discovering these principles provides an obvious strategy for understanding how the cortex functions. Indeed, it has been hypothesized that the cortex is composed of elementary information processing modules. For almost a century anatomists have observed remarkable regularity in the cortical microarchitecture: strings of cells derived from a common progenitor cell and having a propensity of being synaptically connected are arranged to form small columns orthogonal to the cortical surface. These microcolumns are hypothesized to be the elementary functional units of cortical circuitry. If one were able to understand their organizing principles, the task of understanding how the cortex works would be simplified immensely. Discovering the function of these elementary modules would be analogous to the discovery of the gene, which ultimately led to the molecular revolution of the 20th century. So far, these structures could not be studied in detail due to technical limitations. To understand the function of a microcolumn, it is imperative to simultaneously monitor the activity of all its constituting neurons in vivo. It is our goal to overcome these technical challenges and develop in-vivo methods to study an entire microlumn. We propose to develop in vivo microscopy based on 3D random-access multi-photon (3D-RAMP) excitation. This tour de force microscope will employ a series of acousto-optical deflectors operating at long wavelengths that will generate any desired 3D scanning path at frame rates two orders of magnitude faster than current state-of-the-art two-photon imaging systems. This will allow simultaneous in-vivo recordings of the activity of an entire column of sister cells across all six cortical layers. The microscope will employ two 3D-RAMP scanners that will enable simultaneous recording and photostimulation of neural activity to assemble the functional connectivity diagram of the microcolumn. Viral and genetic methods will be used to identify and label ontogenetic microcolumns in vivo. Through collaboration their connectome will be assembled. We plan to create a database of the Microcolumn Architecture of the Cortex that will include functional, anatomical and ontogenetic information about the organization of microcolumns across cortical areas, species and animal models of diseases. Our proposal promises to unravel the elementary principles of how cortical circuits are organized to give rise to mental function. If we succeed our results will constitute a quantum leap in our quest to understand the brain.