One of the most important vision of current medical science is to understand neurobiology of human brain. The 2 greatest initiatives are the Human brain project and Human connectome project. Human brain is arguably more complex than other organ in the human body. Each part of the brain has a specific set of function. The problem in working with brain is that several regions contribute to a particular task and same region may contribute to seemingly different tasks. To map the brain and define what part does what is the greatest question of neuroscience.
As early as 1900s, neurologist Korbinian Brodmann studied neuroanatomical regions of cerebral cortex. Cerebral cortex is the anatomical outer layer of the cerebrum composed of folded grey matter. Based on a variety of cellular details Brodmann labelled different areas of the brain and created a map. Interestingly, neuroscientists have used this map for more than a century without updating the map details with modern technology, until now.
A team led by Mathew Glasser collected data from 210 healthy young adults participating in the Human Connectome Project. Data was acquired for measures of structure and function- cortical thickness, brain function, connectivity between regions, topographic organization of cells in brain tissue, and levels of myelin. Until recently brain map was attempted to be created using a single type pf data which can sometimes be misleading. Here the researchers looked for areas in the cerebral cortex where they could see significant changes in two or more properties, and used these to determine borders on the map. For this the researchers trained a machine-learning algorithm to detect and define borders and establish regions. The study confirmed the existence of 83 previously reported brain areas and identified 97 new ones. The study extended that everyone had all the regions but with varying size indicating that this may contribute to individuality.
Glasser comments, “This map you should think of as version 1.0. There may be a version 2.0 as the data get better and more eyes look at the data. We hope the map can evolve as the science progresses”.
This study has been able to find and affirm regions that have been assumed to be present and also have shown that certain additions proposed earlier where indeed true. For example, In the 1950s, German researchers noticed a patch on the side of the brain in which neurons had little myelin, compared with neighboring regions. The findings had gained little attention. But such findings are upheld according to the new study. The study also showed that certain regions known to be a single part can be subdivided into many regions. For example, it was discovered that a large region near the front of the brain, the dorsolateral prefrontal cortex, actually is made up of a dozen smaller zones.
It should be noted that the different regions don’t possess a perfect demarcation. The boundaries are a bit hazier than expected to be and are not rigid. There are small overlaps everywhere. The best analogy is the boundaries look like political boundaries of countries than the geographical boundaries.
1. Glasser M, Coalson T, Robinson E, Hacker C, Harwell J, Yacoub E et al. A multi-modal parcellation of human cerebral cortex. Nature. 2016. http://www.nature.com/nature/journal/vaop/ncurrent/full/nature18933.html
2. Linda Geddes. Human brain mapped in unprecedented detail. http://www.nature.com/news/human-brain-mapped-in-unprecedented-detail-1.20285
3. A new map of the human brain could be the most accurate yet, as it combines all sorts of different kinds of data. This might finally solve a century of disagreements over the shapes and positions of different brain areas; Nature Video. https://www.youtube.com/watch?v=UHDfvfYCY0U