Engineering human neural networks

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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.