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Is the mind an emergent property of the brain, or is it something… else? Cartesian dualism is a polarizing topic, but like many other ideas that we thought were the province of philosophers, we’re getting light shed on it from a surprising source. Researchers from the Human Connectome Project (HCP) have just released our best-ever functional map of the human brain. It’s twice as finely detailed as anything that has come before it — and it’s tiptoeing closer to settling the mind-body problem. As it turns out, the brain as computer analogy has its shortfalls.
“The brain is not like a computer that can support any operating system and run any software,” says neuroscientist David Van Essen, Principal Investigator of the Human Connectome Project. “Instead, the software — how the brain works — is intimately correlated with the brain’s structure — its hardware, so to speak. If you want to find out what the brain can do, you have to understand how it is organized and wired.”
Image: Glasser, Van Etten et al
Because different subsurface brain structures look more or less the same from the outside, neuroscientists have heretofore relied mostly on gross anatomy and unfortunate happenstance to tell us what parts of the brain did what. (Here’s looking at you, Phineas Gage and Patient H.M.) Structure and function are tightly coupled in the brain, down to the molecular level. But the brain does so many things. Missing borders between brain structures can badly compromise our ability to understand how the brain works.
The HCP has been working for nigh unto six years to shed light on this problem. Their most recent announcement is impressive: The project just doubled the spatial resolution of our best known functional map. In doing so, they also integrate several different ways of explaining differences between brain regions. The researchers report that they’ve found a total of 180 distinct areas per hemisphere, regions which are bounded by sharp changes in cortical architecture, function, connectivity, and/or topography. This development stands to change neuroscience, by opening up our understanding of the relationship between structure and function.
Using multimodal MRI data from the HCP and a semi-automated approach, the new “parcellation” of cortical function checked its predictions by comparing them with brain scans from hundreds of healthy volunteers, so that the model could divide functional regions with exquisite accuracy. The parcellation divides both the left and right cerebral hemispheres into 180 areas based on physical differences like cortical thickness, functional distinctions like which areas respond to language stimuli, and differences in the connections between functional regions. If you think of it using the metaphor of, say, Google Maps, this approach combines political maps with satellite imagery; the most important divisions are invisible from a zoomed-out perspective, but important all the same.
Like cartographers from the Age of Exploration, brain cartographers are creating a tool for others to use in exploration and discovery. Prior work on the connectome gave us a directional diagram of information flow through the brain, and a startling semantic atlasthat shows where we process the meanings of certain words and abstract topics. This team of researchers hopes that their work will prove an asset to other researchers as they push back the frontier of ignorance.
“We were able to persuade Nature to put online almost 200 extra pages of detailed information on each of the 180 regions as well as all of the algorithms we used to align the brains and create the map,” Van Essen said. “We think it will serve the scientific community best if they can dive down and get these maps onto their computer screens and explore as they see fit.”
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