Mapping the human brain

For more than a hundred years, neuroscientists have argued over a single seemingly simple question: how many different areas make up the brain? A team of scientists at Washington University in St. Louis, Missouri have charted what may be the most accurate map of the brain to date. Andrea Vasquez talks to neuroscientists Matthew Glasser and David Van Essen via Google Hangout.

TRANSCRIPT

For more than a hundred years, neuroscientists have argued over a single, seemingly simple question -- how many different areas make up the brain?

A team of scientists at Washington University in St. Louis, Missouri, have charted what may be the most accurate map of the brain to date.

Reporter Andrea Vasquez talks to Matthew Glasser and David Van Essen, neuroscientists at Washington University's School of Medicine, via Google Hangout.

And, Matthew Glasser and David Van Essen, thank you for joining us.

Thank you.

Our pleasure.

When we're talking about this map of the brain, even when we're talking about road maps, there are different types.

There are some that map topography or roads or state boundaries.

What exactly are you mapping here?

So, we're mapping basically four properties of how the brain is organized.

Its architecture -- so, what is going on at the microscopic level.

Its function -- how different parts of the brain are connected.

And then, how individual areas of the brain are organized.

So, those four key things are what we were mapping to make this new parcellation or map of the brain.

And if I can add just a little bit, our focus is on the human cerebral cortex.

And what we're mapping are the equivalent by analogy of the political subdivisions of the Earth's surface.

We map those on top of maps of the convolutions, or folds, of the cerebral cortex, which are analogous to the mountains and valleys of the Earth's surface.

And this is coming out of a longer-standing project, the Human Connectome Project.

Can you tell us more about that?

That's correct.

The Human Connectome Project started in 2010, and it's wrapping up in its current studies of the young adult Human Connectome.

We studied 1,200 healthy, young adults, and in projects that are just starting as the young adults Human Connectome Project wraps up, we'll be studying the development and structure and function and connectivity in children and in older adults to get a better picture of the entire human life-span.

There are also a number of projects that are focused on comparing connectomes in normals to connectomes in various either neurological or psychiatric diseases.

David, do you remember how many?

There are 13 projects funded already by the National Institutes of Health and several more that are likely to be funded in the coming year or so.

And a connectome -- what exactly does that entail?

A connectome -- I like to say it's a comprehensive map of connections in the brain.

But then I immediately put 'comprehensive' in quotes because it's only to the resolution or ability to resolve the basic units of the human brain.

And for the Human Connectome Project, our resolving power are little, tiny-volume units that are a tenth of an inch or so on a side and literally contain hundreds of thousands of neurons and millions and million of synapses between neurons.

So, we'd like to get even better, but there are technical limits of what one can achieve with modern technology.

I'd say there are two kinds of connectomes that we're interested in measuring here.

One is what we call a functional connectome, and that's basically showing how different brain areas, how their activity correlates with each other.

So, if you put somebody in the scanner, an MRI scanner, and you just have them rest, and let their mind wander and think whatever thoughts they want to think, while you're doing that, we measure the MRI signal, and you look for where different brain areas are showing similar fluctuations in that MRI signal.

That's one kind of connectome.

And then the other kind is structural connectome.

And there we're trying to map the actual physical connections between brain areas, albeit in a very indirect way.

Up until now, there have been other diagrams and maps of the brain, but how have those fallen short, clearly, of what you are now accomplishing and working to keep building up?

There have been maps, or what we call parcellations, of the human cerebral cortex for more than a century.

The classical maps from a century ago are kind of quaint and charming but well out of date.

They're analogous to 16th-century maps of the Earth's surface.

In more recent years, there have been major advances in getting better maps, but previous mapping efforts are focused on one type of information, or what we call one imaging modality at a time.

And, as a consequence, those earlier maps got some regions, some areas more or less correct but missed out on or misidentified others.

So, as Matt said a moment ago, by virtue of looking at four independent types of information at one time, we feel confident that we've gotten more accurate and more comprehensive maps, albeit it's not the end the story.

There's still a lot more to learn.

And how much of a given person's brain would align with some of these maps that are being developed, and how much is shaped by unique experiences and genetic factors?

That's a great question, and the answer is we don't know yet.

What we can say is in the great majority of the hundreds of individuals we examined using the computer algorithm Matt mentioned a moment ago, we can identify nearly all of the 180 distinct cortical areas in each hemisphere in nearly all individuals.

So, they are present and to a high degree accounted for, but they aren't identical.

They differ in size by more than a factor of two from one individual to another.

And then a very interesting subset, about 10% of our population that we've studied, at least some areas are what we call atypical in their arrangement.

They've switched their neighborhood relationship with nearby areas, and so they have the same basic constellation of areas, but it's like California and Nevada had switched their places on the map.

Matt Glasser and David Van Essen, thank you very much for joining us.

Thanks for having us.

Our pleasure.