diffusion MRI
The Amazing Brain: Tight-Knit Connections
Posted on by Lawrence Tabak, D.D.S., Ph.D.
You’ve likely seen pictures of a human brain showing its smooth, folded outer layer, known as the cerebral cortex. Maybe you’ve also seen diagrams highlighting some of the brain’s major internal, or subcortical, structures.
These familiar representations, however, overlook the brain’s intricate internal wiring that power our thoughts and actions. This wiring consists of tightly bundled neural projections, called fiber tracts, that connect different parts of the brain into an integrated neural communications network.
The actual patterns of these fiber tracts are represented here and serve as the featured attraction in this award-winning image from the 2022 Show Us Your BRAINs Photo and Video contest. The contest is supported by NIH’s Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative.
Let’s take a closer look. At the center of the brain, you see some of the major subcortical structures: hippocampus (orange), amygdala (pink), putamen (magenta), caudate nucleus (purple), and nucleus accumbens (green). The fiber tracts are presented as colorful, yarn-like projections outside of those subcortical and other brain structures. The various colors, like a wiring diagram, distinguish the different fiber tracts and their specific connections.
This award-winning atlas of brain connectivity comes from Sahar Ahmad, Ye Wu, and Pew-Thian Yap, The University of North Carolina, Chapel Hill. The UNC Chapel Hill team produced this image using a non-invasive technique called diffusion MRI tractography. It’s an emerging approach with many new possibilities for neuroscience and the clinic [1]. Ahmad’s team is putting it to work to map the brain’s many neural connections and how they change across the human lifespan.
In fact, the connectivity atlas you see here isn’t from a single human brain. It’s actually a compilation of images of the brains of multiple 30-year-olds. The researchers are using this brain imaging approach to visualize changes in the brain and its fiber tracts as people grow, develop, and mature from infancy into old age.
Sahar says their comparisons of such images show that early in life, many dynamic changes occur in the brain’s fiber tracts. Once a person reaches young adulthood, the connective wiring tends to stabilize until old age, when fiber tracts begin to break down. These and other similarly precise atlases of the human brain promise to reveal fascinating insights into brain organization and the functional dynamics of its architecture, now and in the future.
Reference:
[1] Diffusion MRI fiber tractography of the brain. Jeurissen B, Descoteaux M, Mori S, Leemans A. NMR Biomed. 2019 Apr;32(4):e3785.
Links:
Brain Basics: Know Your Brain (National Institute of Neurological Disorders and Stroke/NIH)
Sahar Ahmad (The University of North Carolina, Chapel Hill)
Ye Wu (The University of North Carolina, Chapel Hill)
Pew-Thian Yap (The University of North Carolina, Chapel Hill)
Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative (NIH)
Show Us Your BRAINs Photo & Video Contest (BRAIN Initiative)
NIH Support: BRAIN Initiative; National Institute of Mental Health
The Amazing Brain: A Sharper Image of the Pyramidal Tract
Posted on by Dr. Francis Collins
Flip the image above upside down, and the shape may remind you of something. If you think it resembles a pyramid, then you and a lot of great neuroscientists are thinking alike. What you are viewing is a colorized, 3D reconstruction of a pyramidal tract, which are bundles of nerve fibers that originate from the brain’s cerebral cortex and relay signals to the brainstem or the spinal cord. These signals control many important activities, including the voluntary movement of our arms, legs, head, and face.
For a while now, it’s been possible to combine a specialized form of magnetic resonance imaging (MRI) with computer modeling tools to produce 3D reconstructions of complicated networks of nerve fibers, such as the pyramidal tract. Still, for technical reasons, the quality of these reconstructions has remained poor in parts of the brain where nerve fibers cross at angles of 40 degrees or less.
The video above demonstrates how adding a sophisticated algorithm, called Orientation Distribution Function (ODF)-Fingerprinting, to such modeling can help overcome this problem when reconstructing a pyramidal tract. It has potential to enhance the reliability of these 3D reconstructions as neurosurgeons begin to use them to plan out their surgeries to help ensure they are carried out with the utmost safety and precision.
In the first second of the video, you see gray, fuzzy images from a diffusion MRI of the pyramidal tract. But, very quickly, a more colorful, detailed 3D reconstruction begins to appear, swiftly filling in from the top down. Colors are used to indicate the primary orientations of the nerve fibers: left to right (red), back to front (green), and top to bottom (blue). The orange, magenta, and other colors represent combinations of these primary directional orientations.
About three seconds into the video, a rough draft of the 3D reconstruction is complete. The top of the pyramidal tract looks pretty good. However, looking lower down, you can see distortions in color and relatively poor resolution of the nerve fibers in the middle of the tract—exactly where the fibers cross each other at angles of less than 40 degrees. So, researchers tapped into the power of their new ODF-Fingerprinting software to improve the image—and, starting about nine seconds into the video, you can see an impressive final result.
The researchers who produced this amazing video are Patryk Filipiak and colleagues in the NIH-supported lab of Steven Baete, Center for Advanced Imaging Innovation and Research, New York University Grossman School of Medicine, New York. The work paired diffusion MRI data from the NIH Human Connectome Project with the ODF-Fingerprinting algorithm, which was created by Baete to incorporate additional MRI imaging data on the shape of nerve fibers to infer their directionality [1].
This innovative approach to imaging recently earned Baete’s team second place in the 2021 “Show Us Your BRAINs” Photo and Video contest, sponsored by the NIH-led Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative. But researchers aren’t stopping there! They are continuing to refine ODF-Fingerprinting, with the aim of modeling the pyramidal tract in even higher resolution for use in devising new and better ways of helping people undergoing neurosurgery.
Reference:
[1] Fingerprinting Orientation Distribution Functions in diffusion MRI detects smaller crossing angles. Baete SH, Cloos MA, Lin YC, Placantonakis DG, Shepherd T, Boada FE. Neuroimage. 2019 Sep;198:231-241.
Links:
Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative (NIH)
Human Connectome Project (University of Southern California, Los Angeles)
Steven Baete (Center for Advanced Imaging Innovation and Research, New York University Grossman School of Medicine, New York)
Show Us Your BRAINs! Photo and Video Contest (BRAIN Initiative/NIH)
NIH Support: National Institute of Biomedical Imaging and Bioengineering; National Institute of Neurological Disorders and Stroke; National Cancer Institute
