Dissecting the Fabric of the Cerebral Cortex

大脑皮层容纳了我们的心理功能，如感知、认知和行动。尽管在发现单细胞的特性和分子水平的过程方面取得了重大进展，但我们仍然不知道皮质在电路水平上是如何工作的。问题的实质在于理解通过数万亿连接进行交流的数十亿个神经元是如何协调它们的活动来产生我们的智力的。 我们还远不能同时测量所有无数皮质细胞的活动，并组装它们的物理接线图(连接体)。然而，如果存在支配这种复杂性的潜在原则和规则，那么发现这些原则将为理解大脑皮层如何发挥作用提供一个显而易见的策略。事实上，人们一直假设大脑皮质是由基本信息组成的 处理模块。近一个世纪以来，解剖学家观察到了大脑皮层微结构中显著的规律性：从一个共同的祖细胞衍生出来的具有突触连接倾向的一串串细胞排列成与大脑皮层表面垂直的小柱。这些微柱被假设为皮质回路的基本功能单位。如果一个人能够 了解了它们的组织原理，了解大脑皮层如何工作的任务就会大大简化。发现这些基本模块的功能类似于基因的发现，基因的发现最终导致了20世纪的分子革命。到目前为止，由于技术上的限制，这些结构还不能被详细研究。要了解微柱的功能，必须了解 同时监测其在体内所有组成神经元的活动。我们的目标是克服这些技术挑战，开发体内方法来研究整个微瘤。我们建议发展基于3D随机存取多光子(3D-RAMP)激发的活体显微镜。这台环力显微镜将采用一系列声光偏转器，工作在长波长，将产生任何所需的 帧速率下的3D扫描路径比当前最先进的双光子成像系统快两个数量级。这将允许在体内同时记录所有六个皮质层的一整列姊妹细胞的活动。该显微镜将使用两个3D斜坡扫描仪，可以同时记录和光刺激神经活动，以组装功能连接图 微柱的一部分。病毒和基因方法将被用来识别和标记体内的个体发育微柱。通过合作，他们的连接体将被组装起来。我们计划创建一个皮质微柱架构的数据库，其中将包括关于跨皮质区域、物种和疾病动物模型的微柱组织的功能、解剖学和个体发育信息。我们的提案承诺解开大脑皮层回路如何组织的基本原理 精神功能。如果我们成功了，我们的结果将构成我们在理解大脑方面的巨大飞跃。

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.