Japanese scientists manage to recreate tiny portion of a human brain

A step towards lab-grown BRAINS? Scientists create a mini-neuron network with more precision than ever before in a major breakthrough

A team of researchers in has managed to recreate a tiny portion of a human brain, piece by piece, with more precision that ever before. 

The team connected networks of neurons, the pathways along which information travels through our brains, with remarkable accuracy. 

It could be the first step toward the creation of brains in the lab that mirror our own – although millions of connecting neurons are needed to perform even basic tasks.

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Researchers from the University of Tokyo examined how neurons behave and found that they could be trained to join with one another using a ‘synthetic neuron-adhesive material‘, what they call their microscopic plates.

When the team connected two of these artificial neuron scaffolds together, they found that they were able to transmit electrical signals between them. 

There are a number of practical reasons why scientists hope to realise their ambition of creating a fully-functional artificial brain, and this finding is one small step toward that goal.

Growing brains in a lab could afford us greater understanding of a range of neurological and degenerative disorders, including  Alzheimer’s and Parkinson’s diseases.

While the latest finding is a long way off from achieving this, it does raise some interesting philosophical and ethical questions.

Would a lab grown brain be capable of thinking and, if so, does that make it a person?

To become a full person in the eyes of the law, an artificial brain would need to be conscious, with definitions of what constitutes ‘consciousness‘ still up for debate.  

To make their mini-neural network, the Tokyo team took advantage of recent insights into how neurons behave to create their mini-brain; namely, that geometric shapes can help guide neurons, telling them where and how to grow.

Experts placed neuron cells onto these synthetic microplates, which resemble tiny frying pans, with a circular middle and rectangular handles at either end.

The cell body, the centre of the neuron, was placed in the centre of the pan. 

Its axon and dendrites – the branches of the cell that let neurons communicate with each other – stretched out along the handles. 

WHAT IS A NEURON AND HOW DOES IT WORK?

A neuron, also known as nerve cell, is an electrically excitable cell that takes up, processes and transmits information through electrical and chemical signals. It is one of the basic elements of the nervous system.

In order that a human being can react to his environment, neurons transport stimuli.

The stimulation, for example the burning of the finger at a candle flame, is transported by the ascending neurons to the central nervous system and in return, the descending neurons stimulate the arm in order to remove the finger from the candle. 

A typical neuron is divided into three parts: the cell body, the dendrites and the axon. The cell body, the centre of the neuron, extends its processes called the axon and the dendrites to other cells.Dendrites typically branch profusely, getting thinner with each branching. The axon is thin but can reach enormous distances. 

To make a comparable scale, the diameter of a neuron is about the tenth size of the diameter of a human hair. 

All neurons are electrically excitable. The electrical impulse mostly arrives on the dendrites, gets processed into the cell body to then move along the axon.

On its all length an axon functions merely as an electric cable, simply transmitting the signal. 

Once the electrical reaches the end of the axon, at the synapses, things get a little more complex. 

The key to neural function is the synaptic signalling process, which is partly electrical and partly chemical. 

Once the electrical signal reaches the synapse, a special molecule called neurotransmitter is released by the neuron.

This neurotransmitter will then stimulate the second neuron, triggering a new wave of electrical impulse, repeating the mechanism described above.

‘What was especially important in this system was to have control over how the neurons connected,‘ study first author Shotaro Yoshida said.

‘We designed the microplates to be movable, so that by pushing them around, we could physically move two neurons right next to each other.

‘Once we placed them together, we could then test whether the neurons were able to transmit a signal.‘ 

Neurons communicate with one another through synapses, specialised structures that let chemical messengers travel from one neuron to the next. 

Using a technique to visualise the parts of a synapse, the research team found that the microplate-riding neurons were indeed able to form these communication hubs. 

What was more, the hubs were functional.

When one neuron lit up with electrically charged ions, its partner lit up at precisely the same time. 

While the team aims to further refine the system (only a small fraction of neurons could be successfully connected through working synapses), the results of the study suggest an important step forward in using microplates for research. 

In a written statement, study participant Shoji Takeuchi said: ‘This is, to the best of our knowledge, the first time a mobile microplate has been used to morphologically influence neurons and form functional connections.

‘We believe the technique will eventually allow us to design simple neuron network models with single-cell resolution. 

‘It‘s an exciting prospect, as it opens many new avenues of research that aren‘t possible with our current suite of experimental tools.‘   

Research into the brain typically involves the use of in vitro cultures, which are collections of neurons grown together in a dish. 

A culture represents, in effect, a highly pared-down version of a brain, and one that can be chemically or electrically manipulated. 

While cultures are indispensable to neurological research, they suffer from considerable limitations.

‘In vitro culture models are essential tools because they approximate relatively simple neuron networks and are experimentally controllable,‘ Dr Yoshida added. 

‘These models have been instrumental to the field for decades. The problem is that they‘re very difficult to control, since the neurons tend to make random connections with each other. 

‘If we can find methods to synthesise neuron networks in a more controlled fashion, it would likely spur major advances in our understanding of the brain.‘

The full findings of the study were published in , a journal of molecular machinery. 

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