German neuroanatomist Korbinian Brodmann was the first to map the human cortex in early 20th century. He identified 50 regions, including areas later shown to be involved in visual, language and sensory processing.
The researchers involved in the current study called Human Connectome Project, included David Van Essen, and Matthew Glasser ? lead authors of the paper. The project involved a consortium of laboratories from the University of Minnesota and Oxford University. It used a powerful, custom-built MRI machine to map brains of 1200 young adults, by carefully delineating the brain regions so that their connections could 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 (areas that 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. ?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.?
?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. ?It quickly became obvious to me that we needed a better way to map the areas in the living brains that we were studying.?
To make this map, Glasser, Van Essen and colleagues pooled data from 210 healthy young adults of both sexes. The researchers combined measures of the thickness of the cortex and the amount of insulation around neuronal cables, with MRI scans of the resting brain and of the brain performing simple tasks, such as listening to a story.
Some of those areas 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. 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.
?We ended up with 180 areas in each hemisphere, but we don?t expect that to be the final number,? Glasser said. ?In some cases, we identified a patch of cortex that probably could be subdivided, but we couldn?t confidently draw borders with our current data and techniques. In the future, researchers with better methods will subdivide that area. We focused on borders we are confident will stand the test of time.?
Scientists 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.
In the century between Brodmann?s map and Glasser and Van Essen?s, many other maps of the cortex have been drawn, showing anywhere from 50 to 200 different areas. The researchers 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.
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.
Individual brain maps also 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.
Source: Washington University School of Medicine
Image courtesy: Washington University School of Medicine