A newly updated map of the human brain shows almost 100 areas

A newly updated map of the human brain may be the most accurate yet, helping solve over 100 years of arguments and showing nearly 100 areas that hadn’t been reported before.

The first hints of the brain’s hidden geography emerged more than 150 years ago. In the 1860s, the physician Pierre Paul Broca was intrigued by two of his patients who were unable to speak. After they died, Broca examined their brains. On the outer layer he found that both had suffered damage to the same patch of tissue. That region came to be known as Broca’s area. In recent decades, scientists have found that it becomes active when people speak and when they try to understand the speech of other people.

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A new map based on brain scan data collected by the Human Connectome Project. The data revealed 97 new regions, bringing the total to 180. Credit: Matthew F. Glasser, David C. Van Essen.

Last week, in what many experts are calling a milestone in neuroscience, researchers published a spectacular new map of the brain, detailing nearly 100 previously unknown regions – an unprecedented glimpse into the machinery of the human mind. The map is a detailed look at the part of the brain that handles all your senses, as well as your motion – plus some other functions like problem-solving and emotional regulation. It’s called the cerebral cortex, and it’s the brain’s outer layer of nerve tissue. The map was assembled using data from the Human Connectome Project, an effort funded by the National Institutes of Health to better understand how the human brain works by compiling as much neural data as possible.

“To understand the brain and to fix it, we really need to know the circuit diagram and all the parts, how they work and how they interact,” says David McCormick who did not take part in the study. “And this paper is a major advance toward understanding the circuit diagram.”

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A map of myelin content (fatty insulation surrounding the brain’s nerves) in the left hemisphere of the cerebral cortex. Credit: Matthew F. Glasser, David C. Van Essen.

Putting together all that data helped identify these new areas. The cortex’s thickness, for instance, varies from brain region; in some places, it is as thin as 1mm and in others, as thick as 4.5mm. Overlaying that with imaging that reveals the brain’s blood flow, called fMRI, and adding information about the fatty insulation surrounding the brain’s nerves let the researchers create new boundaries for brain areas, says study co-author Matthew Glasser, a neuroscientist working on his MD at Washington University. Anywhere two of these things changed together in the brain was where the neural cartographers put a new boundary.

Using this method, the researchers divided the human brain into 180 cortical areas, including 97 new ones. One of these regions, for example, is a big groove called POS2 that’s right in front of the visual cortex, which is the part of the brain that allows you to see. The researchers identified the area by looking at the fMRI data and noticing that POS2 stayed deactivated when the subjects were solving a math problem but sprung into action when they relaxed. No one knows what it does, Glasser says. But that might be because no one’s known to look at it before. “What they found was about twice as many areas as was known, which is a huge leap in the neuroscience of human brain,” McCormick says.

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VideoCredit: Matthew F. Glasser, David C. Van Essen.

Some, like Simon Eickhoff a neuropsychiatrist professor at Heinrich-Heine University Düsseldorf in Germany, dispute the novelty of these regions. For instance, some locations identified in today’s research had been documented before — just not in nearly as much detail. “I completely support the statement that they showed now in a systematic fashion, looking at the entire brain, using a multimodal approach, that there are subdivisions here and there and there,” he says. “But I would be careful about calling these areas completely new.”

The interpretation of fMRI data has also been called into question in other studies. The concern is that fMRIs can create false positives, skewing the statistical analysis researchers perform to identify the brain areas that are activated when performing particular tasks. But in this study, Glasser says, researchers made sure other features, such as cortex thickness and fatty insulation, corroborated the fMRI data before a new boundary was drawn. “One of the strengths of the study is that we’re making use of this corroboration,” Glasser says.

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The pattern of brain activation (red, yellow) and deactivation (blue, green) in the left hemisphere when listening to stories while in the MRI scanner. Credit: Matthew F. Glasser, David C. Van Essen.

The map is mostly useful for future research efforts. The researchers trained a machine learning algorithm to be able to identify the fingerprints – like functions and connectivity – of the 180 cortical areas. Researchers will be able to use the algorithm to find the same areas in their own research subjects. The algorithm is for now 96.6 percent accurate – not good enough yet.

Despite that, the algorithm is very impressive, McCormick says. And it could help neuroscientists, neurosurgeons, and neurologists in their work and research. Down the line, the map could help researchers understand how people think and do things in different ways, by providing newly defined areas to study and helping consolidate knowledge we already have. “It’s going to help us understand amazing things about behavior and how the cortex underlies it,” McCormick says.

References

[1] “This new brain map shows almost 100 areas never described before” post written by Alessandra Potenza in The Verge.

[2] “Updated Brain Map Identifies Nearly 100 New Regions” post written by Carl Zimmer in The International New York Times.

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