“M” Marks the Spot


A completely new method for mapping brain anatomy will give us a much clearer idea of where some areas end and others begin.

A brain gets all snazzy with myelin fMRI maps.

The new technique compares two different kinds of fMRI data to show where there’s myelin – the sheath that only surrounds long-range neuron branches (axons) – at a speed and level of detail never possible before. This breakthrough will help scientists look for the differences between the brain’s “surface streets” and its “highways” while that brain is actually working.

See, scientists have known since the late 1800s that the it’s pretty easy to find the borders of brain structures, by looking for the switch from gray matter (tissue containing cell bodies) to white matter (axons surrounded by myelin)1. Problem was, the only way to look for white matter was to cut open dead brains and chemically stain them in a certain way.

Earlier this year, a technique called SAXS-CT finally allowed scientists to take 3-D myelin-sensitive x-rays – but still, these were only static images, and they didn’t include the rainbow-colored detail of fMRI scans.

Now, though, we can look forward to lots of fun, safe, noninvasive myelin movies, an article in the Journal of Neuroscience reports:

We use the ratio of T1w/T2w [fMRI] image intensities to eliminate the MR-related image intensity bias and enhance the contrast to noise ratio for myelin. Data from each subject were mapped to the cortical surface and aligned across individuals using surface-based registration. The spatial gradient of the group average myelin map provides an observer-independent measure of sharp transitions in myelin content across the surface—i.e., putative cortical areal borders.

In other words, the technique compares data from T1-weighted fMRI and T2-weighted fMRI, which are two different ways an fMRI scanner can image tissue. Since myelin – conveniently – looks different on each type of scan, the method uses those differences to help it spit out fMRI-like images showing where the myelin is. And it’s convenient, too: all it takes to run the data is a ten minute fMRI scan.

What’s really impressive (to me) is that this technology was developed by a graduate student, Matthew Glasser of Washington University. He completed his research with help from the Human Connectome Project – a group of researchers on an epic quest to map every connection in the whole human brain. This is certainly a step in that direction.

The next steps are also going to be pretty cool:

The technique will make it possible for the Connectome Project to rapidly map myelination in many different research participants. Data on many subjects, acquired through many different analytical techniques including myelination mapping, will help the resulting maps cover the range of anatomic variation present in humans.

In short, it may not be too long before this technique (and others) start to give us a clearer picture of just how each of our brains is anatomically and functionally unique – and in what ways they’re very similar.

I mean, aren’t you just a little curious about that?

__________

1. So the next time someone tells you to “use that gray matter,” you can be a smartass and say, “I’ll need to use my white matter too!”

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