Engineering human neural networks

目前，我们对人脑的了解受到对其基本单位神经元/星形胶质细胞组合的最基本细胞功能的无知的限制。大脑功能的动物模型受到它们的物理特性的限制，这些物理特性在某些重要方面与我们的不同。此外，动物的大脑不能以理解任何复杂系统或机器所必需的方式从头开始构建。该项目的主要目的不亚于建立一个人类大脑最基本功能的模型，以阐明人类神经元如何处理和保留信息，以及它们如何扩展信息记忆-它们如何“学习”。开始，我们使用生长停滞的人类肿瘤细胞系（NT 2/D1细胞），然后使用“分化”过程将其发育成神经元和星形胶质细胞的紧密连接的混合物，其比例与我们自己大脑中的比例相似，该过程模拟人类胚胎在生命的前几周的发育，并且如果三维生长，则导致微型人类神经元组织。一旦形成，这些培养物的行为就像动物的大脑切片一样，因为星形胶质细胞以相同的频率脉动，神经元可以像人脑一样在网络中进行通信。我们可以完全操纵分化过程，甚至可以在细胞中插入额外的基因，使用多光子激光技术和钙成像来可视化功能。该系统的主要特点是，与动物切片模型不同，细胞没有受到创伤，也不会慢慢死亡。这些培养物可以存活长达6个月，因此最基本的神经元/星形胶质细胞功能可以在真实的时间内一秒一秒地被跟踪。因此，该培养系统与现有的动物模型相比具有两个相当大的优点，即它是根据需要“定制的”，以了解复杂神经元过程的最基本步骤，并且它可以被非侵入性地监测以研究更高级的神经元/星形胶质细胞行为。为了建立一个人类大脑最基本功能的功能模型，需要两个细胞模型，首先是NT 2/D1细胞，然后是人类干细胞，以及3-D矩阵的工程和组装，以构建生物神经元网络（bNN），它应该能够存储信息作为记忆，以及通过细胞网络处理数据，然后做出某种形式的反应。由于即使是人类大脑组织的小区域也具有处理和存储以及与近端和远端组织进行通信的能力，因此我们必须建立一种多隔室方法，其中连接了几个基本的生物网络，以促进更高级的处理。最终，NT2.D1细胞（以及最终的人类干细胞）将沿着沿着的3-D神经元网络生长，该神经元网络将具有可证明的联网能力，这将使用多光子激光技术以及钙成像进行监测。一旦基本的bNN网络形成，这些网络将受到电子挑战，试图诱导细胞彼此形成新的链接（突触）以保留信息，这是记忆的基础。这个过程被称为突触可塑性，是连接多个bNN的重要步骤，以确定是否可以进行更高级的处理，如视觉记忆发展。这是一种非常基本的“训练”形式，其中链接的bNN可以交流，处理和“记住”信息。如果成功，这将是现有的基本人类神经元处理的最先进的模型，并将为适应人类神经元活动的许多其他探索铺平道路，无论是与现有的动物数据相比，都将促进可以模拟不同人类条件的bNN的构建。

Currently our knowledge of the human brain is restricted by ignorance of the most basic cellular functions of its fundamental unit, the neurone/astrocyte combination. Animal models of brain function are limited by their physical which differ in some vital respects to ours. In addition, the animal brains cannot be built from scratch in the manner that is necessary to understand any complex system or machine. The primary aim of the project is no less than to build a model of the most basic functions of the human brain to cast light on how living human neurones process and retain information and how they expand their memory of information-how they 'learn'. To begin we using a growth arrested human tumour cell line (NT2/D1 cells), which is then developed into an intimately connected mixture of neurones and astrocytes in similar proportions to those in our own brains using the 'differentiation' process which mimics human embryo development over the first few weeks of life and results in a miniature human neuronal tissue if grown in three dimensions. Once formed these cultures behave like brain slices of animals, as the astrocytes pulse at the same frequencies and the neurones can communicate in a network as the human brain does. We can fully manipulate the process of differentiation and even insert extra genes in the cells to visualize functions using multiphoton laser technology and calcium imaging. The key features of the system are that unlike an animal slice model, the cells are untraumatized and not slowly dying. The cultures can live for up to 6 months and so the most basic neuronal/astrocytic functions can be followed second by second as they happen in real time. The culture system has thus two considerable advantages over existing animal models, in that it is 'custom built' as required in order to understand the most basic steps of complex neuronal processes and it can be non-invasively monitored to study more advanced neuronal/astrocytic behaviour. To build a functioning model of the most basic functions of the human brain requires both cellular models, initially the NT2/D1 cells and then human stem cells, as well as the engineering and assembly of 3-D matrixes to construct biological neuronal networks (bNNs) which can should be able to store information as memory, as well as process data through a network of cells and then make a form of response. As even small areas of human brain tissue contain the ability to process and store and communicate with proximal and distal tissues, so we must build in a multi-compartmental approach where several basic biological networks are connected facilitating more advanced processing. Ultimately, the NT2.D1 cells (and eventually human stem cells) will be grown along 3-D neuronal networks which will have provable networking capability, which will be monitored using multi-photon laser technology as well as calcium imaging. Once the basic bNN networks have been formed, these will be challenged electronically to try to induce the cells to form new links (synapses) with each other to retain information, which is the basis of memory. This process, known as synaptic plasticity, is a vital step connection of multiple bNNs to determine if a more advanced processing such as visual memory development can take place. This is a very elementary form of 'training' where the linked bNNs can communicate, process and 'remember' information. If successful, this will be the most advanced model of basic human neuronal processing in existence and will pave the way for the adaptation to many other explorations of human neuronal activity, both compared with existing animal data and will facilitate the construction of bNNs which can be made to simulate different human conditions.