From axons to tracts: A journey through the brain's wiring

Created by Luis Concha and Daniel Torres
University of Alberta, Canada.

Please note: This work is licensed using Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.

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The complex circuitry interconnecting different areas in the brain, known collectively as white matter, is composed of millions of axons organized into fascicles and bundles. Upon macroscopic examination of sections of the brain, it is difficult to discern the orientation of the fibers. The same is true for conventional imaging modalities. However, recent advancements in magnetic resonance imaging (MRI) make such task possible in a live subject. By sensitizing an otherwise typical MRI sequence to the diffusion of water molecules it is possible to measure their diffusion coefficient in a given direction1. Normally, the axonal membrane and myelin sheaths pose barriers to the movement of water molecules and, thus, they diffuse preferentially along the axon2. Therefore, the direction of white matter bundles can be elucidated by determining the principal diffusivity of water. The three-dimensional representation of the diffusion coefficient can be given by a tensor and its mathematical decomposition provides the direction of the tracts3; this MRI technique is known as diffusion tensor imaging (DTI). By connecting the information acquired with DTI, three-dimensional depictions of white matter fascicles are obtained4. The virtual dissection of white matter bundles is rapidly becoming a valuable tool in clinical research.

Our journey begins with a transverse section of tightly packed axons as seen through light microscopy. Although represented as a two-dimensional "slice", we see that these axons in fact resemble tubes. A simulation of water molecules diffusing randomly inside the axons demonstrates how the membranes and myelin hinder their movement across them and shows the preferred diffusion direction --along the axons. The tracts depicted through DTI slowly blend in and we ride along with them. As we zoom out even more, we realize that it is a portion of the corpus callosum connecting the two sides of the brain we were traveling on and the great difference in relative scale of the individual axons becomes evident. The surface of the brain is then shown, as well as the rest of the white matter bundles--a big, apparently chaotic tangle of wires. Finally, the skin covers the brain.

With the exception of the simulated water molecules, all the data presented in the animation is obtained through microscopy and MRI. Computer algorithms for the extraction of the cerebral structures and a custom-built graphics engine make our journey through the brain's anatomy possible in a living person.

Micrograph courtesy of Dr. Christian Beaulieu, University of Alberta.
Music by Mario Mattioli.

References:
1. Stejskal, E.O., et al., J. Chem. Phys., 1965. 42:
2. Beaulieu, C., NMR Biomed., 2002. 15:435-55.
3. Basser, P.J., et al., J. Magn. Reson. B, 1994. 103:247-54.
4. Mori, S., et al., NMR Biomed., 2002. 15:468-80.

Category:

Science & Technology

Tags:

• brain
• MRI
• diffusion
• tractography
• axons
• neurons
• CG
• 3D
• cgfx

[TheREALBoris]

that was the most party-like journey through the human brain ive ever been on!

[PalluxoMediaOfficial]

"millions of axons" ?

More like billions or even trillions!

[OriginalRipndip]

If I took a Brain Anatomy class or even Brain Psych tis would be cool. BUT I HAVE NO IDEA what just happened!

Hmm maybe a good youtube video to start me off.. any suggesions?

[happinesson]

virtual 3D picture of the brain is fantastic!

[VinkoRajic]

I can use telepathy, I am looking for some place to make experiment and confirm it. My telepathy works to 100% and all the time.

[GoIdenVegas]

@sabbathcrazy Anywhere but in the grocery, please!

[JazzDanca]

Enlightenment, will you please leave this planet. We do not need idiots like you with extremely low intelligence and sensitivity on planet earth.

Get off now!! YOU'RE A WASTE OF SPACE!!

[C00lblkatheist]

@TheLoserKingdom I know this is old, but not all neurons have one axon. There are some diffuse-projecting neurons where they have multiple axons, and axon terminals. One is the cholinergic neuron that projects to the hippocampus, temporal lobe, septal nucleus etc.

[enlightenment5]

Super cunts of USA copied Nazism of the Brain. And now the curse of Nazi Mind Scientists on the USA. Inside the CIA - human centipede metaphor - the offensive disgust - corrupt Caucasians smelling the arse of Indian Patels, hiding under the frocks of women, the two mind perpetrators addicted in trance with the smell of each other farts! If they both live in Christian lands, have they held a Bible? if not, they should be banished to another planet or join the savages of jungles of Black Africa.

[CutaayMitzieaa919]

héhè_ÁñÿónE_wânnÁ_chÂt_wIth_mÈ­_Î_fÈEl_sò_lønèlY_tÔDÀÿ...

[MariosLasagna]

I love my axons because they carry information away from the cell body of my neurons! Without them, information is stagnant.

[ivanriches]

Beautiful stuff