A detailed new map by researchers at Washington University School of Medicine in St. Louis and associates* lays out the landscape of 180 areas of the cerebral cortex in painstaking detail; 97 of these areas have never been previously described.

The new map is intended to help researchers studying brain disorders such as autism, schizophrenia, dementia and epilepsy. They will be able to use it to understand differences in the brains of patients with these diseases, compared with adults who are healthy. It also will accelerate progress in deciphering the workings of the healthy brain and elucidating what makes us unique as a species, the researchers say. The new map will also be vital for neurosurgeons.

The work was published today, July 20, in Nature.



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The researchers drew upon data and methods generated by the Human Connectome Project, a five-year, multimillion dollar study led by David Van Essen, PhD, the senior author on this paper. The Human Connectome Project used a powerful, custom-built MRI machine to map the brains of 1,200 young adults. This new study complements the Human Connectome Project by carefully delineating the brain regions so that their connections can be more accurately mapped.

The new map divides both the left and right cerebral hemispheres into 180 areas based on physical differences (such as the thickness of the cortex), functional distinctions (such as which areas respond to language stimuli), and differences in the connections of the areas.

“The brain is not like a computer that can support any operating system and run any software,” said Van Essen, the Alumni Endowed Professor of Neuroscience at Washington University Medical School. “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.”

The researchers mapped the cortex, a layer of neural tissue that encases the rest of the brain like a crumpled sheet of paper. The cortex is important for sensation, attention, memory, perception, thought, language and consciousness.

Beyond Brodmann’s areas

The new study is intended to replace previous maps, such as Korbinian Brodmann’s map of the human cortex, created in the first decade of the 20th century, which identified 50 regions. “My early work on language connectivity involved taking that 100-year-old map and trying to guess where Brodmann’s areas were in relation to the pathways underneath them,” said Matthew Glasser, PhD, of Washington University Medical School. “It quickly became obvious to me that we needed a better way to map the areas in the living brains that we were studying.”

Until now, most brain maps have been based on a single type of measurement. To make the new map, the researchers pooled data from 210 healthy young adults of both sexes, combining measures of the thickness of the cortex and the amount of insulation around neuronal cables, using MRI scans of the resting brain and of the brain performing simple tasks, such as listening to a story. The information also included measurements of brain function, connectivity between regions, topographic organization of cells in brain tissue, and levels of myelin, which speeds up neural signaling.

In the new map, some of the 180 areas identified are clearly involved in particular tasks, such as 55b, which lights up with activity when a person hears a story. Others contain a map of a person’s field of vision, or are involved in controlling movement. But most areas probably will never be identified with a single function, because they don’t do just one thing, but instead coordinate information from many different signals.

Many other maps of the cortex have been drawn, showing anywhere from 50 to 200 different areas. But the researchers say they improved on previous maps by precisely aligning the brains to a common coordinate system before analysis, using an algorithm developed by colleagues at Oxford University, and incorporating the highest-quality MRI data available. The researchers also verified that their method could be applied to individuals by producing maps of the brains of a different set of 210 healthy young adults.

Guiding neurosurgeons

The results are a precise map with unusually crisp borders and an algorithm capable of locating the areas in individual brains, even though each individual is unique in terms of the pattern of cortical folds and in the size and shape of areas on the cortical map.

“In the past, it was not always clear whether the results from two separate neuroimaging studies referred to the same area or not,” Glasser said. By using the new map and alignment algorithm, results of separate studies could be more accurately compared.

Better individual maps of the brain could help neurosurgeons avoid damaging the most important areas, such as those involved in language or motor function, and could guide treatment for neurological or psychiatric illnesses. Different types of dementia, for example, are characterized by degeneration in different areas of the brain. Clinicians could use the individual maps to personalize treatment, based on the areas affected, or to monitor response to treatment.

Like cartographers of old, brain cartographers primarily are providing a tool for others to use in exploration and discovery.

“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.”

* University of Oxford; Imperial College, London; University of Minnesota; Radboud University; Radboud University Medical Centre.