A technique to identify myelination in order to map the layout of cortical areas in the human brain has been developed by researchers led by David van Essen at the Washington University School of Medicine in St. Louis. It is generally known that myelination levels are different throughout the cerebral cortex. The best way to assess it is to investigate the brain post mortem. Using the new technique of myelination mapping, it will be possible to accurately map individual cortical areas in vivo. The researchers used their method on a group of control subjects and found an excellent agreement between the spatial gradients of the myelin maps and already published anatomical and functional information about cortical areas, mostly based on post-mortem histology.
Using data from T1 and T2-weighted MRIs, the team has been able to use the ratio of image intensities to eliminate the MR-related image intensity bias and enhance the contrast to noise ratio for myelin. To map it to the cortical surface, they used a customized algorithm.
Areas with high myelination levels, such as the motor, somatosensory, visual and auditory cortices, are involved with early processing of information. These areas are highly populated with brain cells using less complex intercellular connections. Areas with lower myelination, such as the prefrontal, temporal and parietal cortices, are less densely packed, due to larger cell size and more complex intercellular connections.
Better brain mapping is supposed to provide a greater understanding in how a physiological brain works and possibly help in diagnosis, follow-up and treatment of pathological brain conditions. Comparing human myelination maps with animal brain maps might help to understand a little more about how the brain has evolved. Van Essen intends to map the myelination in a vast amount of research participants, to cover the range of anatomic variation in the human brain.
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Abstract in The Journal of Neuroscience: Mapping Human Cortical Areas In Vivo Based on Myelin Content as Revealed by T1- and T2-Weighted MRI