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Human Connectome Project

Human Connectome Project

Mapping the human brain…

An ambitious project, started in 2009, to map the pathways of the human brain is finally becoming a reality. The Human Connectome Project (HCP) aims to provide a comprehensive map of the brain presented in 3D images with which users can “fly through major brain pathways, compare essential circuits, zoom into a region to explore the cells that comprise it, and the functions that depend on it.”

Scientists already have some idea of the brain is wired. They know that the cerebral cortex makes up 80% of the human brain, but holds only a fifth of its neurons. They also know that the cortial surface contains at least 150 different areas.

Such knowledge is already helping to uncover the cause behind some disorders such as schizophrenia, Alzheimer’s and addiction, which are thought to be due to miswiring of neurons.

But since the variance between people is substantial, creating an accurate model that can be applied to everyone is a mammoth task.

Nevertheless, the Connectome team hopes its model of structural and functional neural connections will help us better understand the complete details of our neural network.

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Human Connectome Project Images

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Human Connectome Project

Image Credit: Human Connectome Project, 2012.

Whilst the project is certainly a massive undertaking, it’s not even the tip of the iceberg. There are still years of work.

Jeff Lichtman, a neuroscientist at Harvard University hopes to take such research one step further by mapping the entire brain. At his laboratory he uses a machine known as an automated tape-collecting lathe ultramircrotome (Atlum), which essentially slices human brain into 1mm thin sheets and attaches them to sticky tape ready to be photographed by a high-power electron microscope. The pictures are then combined into 3D images; revealing the inner working of the brain.

The problem using this method is time – to gather enough slices to create 1mm of mapable brain tissue requires 30,000 slices and takes 6 days. Lichtman calculated how long it might take to image a full mouse brain – the answer was 7,000 years.

Human brains have 85bn neurons in brain. Each one forms 10,000 connections, through synapses with other nerve cells. Lichtman estimates there are somewhere between 100tn and 1,000tn connections in our brains.

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Human Connectome Project

human connectome project images-3

Human Connectome Project

Image Credit: Human Connectome Project, 2012.

Another factor that makes the task even more challenging is that the brain is made up of four different types of brain cells – Golgi, Betz, Renshaw, Purkinje – that all behave differently.

“To map the human brain at the cellular level, we’re talking about 1m petabytes of information. Most people think that is more than the digital content of the world right now…

“I’d settle for a mouse brain, but we’re not even ready to do that. We’re still working on how to do one cubic millimeter.”

Some scientists working on the Human Connectome project believe that Lictman’s work is overkill, claiming the HCP work is still intricate enough to teach us lots about how the brain works. Olaf Sporns, a neuroscientist at Indiana University, who coined the term ‘connectome’ said:

“If you want to study the rainforest, you don’t need to look at every leaf and every twig and measure its position and orientation. It’s too much detail,”

“It’s like trying to describe the Mona Lisa by fixing the positions of the atoms and molecules that make up the paint.”

But this isn’t stopping Lichtman, who is now working with a German company to develop a multibeam microscope to speed up imaging. So while Sporn and other neuroscientists are focusing on what can be done with today’s technology, Lichtman is hoping a break through in technology will help his ambitious project become possible.

Check out the $40m Human Connectome Project and its progress here>>>

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  1. Ian Sample: Quest for the connectome: scientists investigate ways of mapping the brain. The Guardian, 05/07/2012.
  2. Image Credit: Human Connectome Project, 2012.

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