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The Human Brain's Unique Wiring Patterns May Be What Makes It Special

By: April Feng


The human brain is an extremely complex organ. It is abnormally large when compared to human body size, and it also contains many specialized areas that help humans process information differently from other animals. Although the brain still has many mysteries left to be solved, new technologies in recent years have helped neuroscientists to make several responses as to why the human brain is so special.


Magnetic resonance imaging (MRI)or more specifically, a version called diffusion tensor imaging (DTI)has played a large role in these discoveries. This imaging can map out the human brain by estimating the positioning of the “white matter,” or nerve fibers, and where they link to. Then, a connectome, or a combined image of the nerve links, can be created to help scientists to understand exactly how the human brain processes information.


However, scientists are still unsure on how distinctive nerve wiring patterns in human brains cause the different cognitive levels found in humans and other animals. Comparative connectomics, a new methodology, has identified some answers on how efficient brain wiring can improve cognition. It has even identified a unique evolutionary aspect of brain wiring cells, which may provide further information on psychiatric disorders.


In theory, the most efficient connectome would be one with all nerve cells connecting to each other, or the one-to-many design. However, this would require too much space and energy. Thus, the one-to-one design would be much more realistic, with each nerve cell only connecting to one other nerve cell. But this approach is too inefficient because information would be forced to take longer paths than necessary to get from one point to another.


Yaniv Assaf of Tel Aviv University gives another answer. “Real life is in the middle,” he says. After surveying the connectomes of 123 species, Assaf’s team found many patterns. Most notably, the number of steps to get from point A to point B was approximately the same in each species, meaning that they all used a similar wiring design.


The difference lies in the number of long-range connections that each species had. While other animals tended to “talk” within each hemisphere’s local network, humans had more connections between both brain hemispheres. According to anthropologist James Rilling of Emory University and Martijn van den Heuvel of Vrije University Amsterdam, these unique long-range connections may have boosted communication efficiency in human brains. Additionally, they also tied together “high level associate areas in the cortex involved in language, tool use, and imitation.”


Although brain imaging is limited, genomics can fill in the remaining gaps of information. Menno Creyghton of the Erasmus University Medical Center in the Netherlands discovered enhancers called oligodendrocytes, which act as enhancers to brain connectivity efficiency. These new discoveries may serve to revolutionize what neuroscientists previously thought about the unique connections of the human brain.



https://www.scientificamerican.com/article/how-human-brains-are-different-it-has-a-lot-to-do-with-the-connections/


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