Mapping the connections in the brain

DSI image of white matter tracts in the brain

White matter tracts seen from below – colour-coding shows the direction of fibre tracts. Figure from the Human Connectome Project gallery by LONI / UCLA & Martinos Center of Biomedical Imaging / MGH.

The BBC ran a story today on the Human Connectome Project. The story features a set of colorful pictures, which represent some of the first results of the massively ambitious, $40M endeavor to map the human connectome. The BBC article has the pretty pictures, while a recent advertorial* in Science has a bit more of the technical detail.

The Connectome Project attempts to map the neural connections in the human brain; the connectome (cf. genome) is unique for everyone, a result of genetic and environmental factors, as well as what we’ve learned and experienced in life.

The enormity of the project dwarfs the mapping of the human genome. So far, the connectome of only one species has been mapped: the round worm C. elegans has had the 7000 connections of its 300 neurons mapped. This took ten years, and the human brain has about 100 billion times more connections than the C. elegans. So it’s a huge technical challenge to put it mildly.

However, the pretty pictures on the BBC story are not the connections of individual neurons. Instead, they are the “superhighways” of the brain, the bundles of thousands of axons that allow the different parts of the brain “talk to each other”.

These connections are mapped using the magnetic resonance (MR) scanner, that also produces the pics of “blobs” of activation that we are used to seeing in cognitive neuroscience studies (fMRI) or the generic anatomical images used e.g. in medical diagnostics. It is just a different imaging sequence that looks at the diffusion of tiny water droplets in the brain tissue. Water droplets flow easier along these fibres than across them, allowing the system thus to calculate the paths of these fibre tracts, and then these can be visualised in all the colours of the rainbow!

These diffusion images have been around for a while, so what’s so special about them? Well, these images are produced using a new “connectome scanner”, which is a souped-up MR machine that produces larger magnetic gradients than “normal” scanners. It is the gradient rather than the strength of the magnetic field itself that is crucial for this type of imaging. Also, the pics are the product of new data processing and visualisation software developed for this purpose by the crew at the Massachusetts General Hospital Martinos Center for Biomedical Imaging and the Laboratory of Neuro Imaging at the UCLA. The result: finer and more accurate tract maps.

So, consider these first images as “tasters” of what is to come, with more brains being scanned, and more specific research questions are being asked.

Much more info, including academic papers on the technical details and links to many more news stories:

This post was published also at my Google+ feed under tags #sciencesunday   #neuroscience   #connectome

* (this is one of their “Product articles”, essentially an ad paid for by the vendors and manufacturers of the cool devices that the research is done on, but it explains the general matter pretty well.)

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