SHILL Issue 71

@The_AO8
"inside the artist mind"
As reported in the first series thread, the capacity
of MRI of “measure” the movements of water
makes possible the drawing of diffusion tensor
imaging (DTI), which is particularly useful for visualization
of axonal white matter pathways (ie,
nervous fibers) in the brain. Indeed, since axons
are tubular impermeable structures (allowing
water diffusion in one direction), white matter
structures are very highly anisotropic. This allow
MRI to calculate the direction of the fibers.
Using voxel-by-voxel maps of anisotropy data,
computer modeling can then estimate the most
likely location of white matter tracts (i.e., wide
sets of axons) by forming likely fiber paths between
voxels (known as streamlines).
Apart for studying purposes (in vivo), DTI reconstructions
may be helpful to plan surgical intervention,
when demolitive operations are planned
(i.e., trying to avoid particularly important structures).
Here represented is the pyramidal tract,
better known as corticospinal tract (CST), is the
path that carry movement-related information.
It starts in the cerebral cortex (where movement
is ideated; first or upper motoneuron) to the spinal
cord (from there a second (lower) motoneuron
deliver the information to the muscles).
Interestingly, in a cerebral structure of the brainstem
called “pyramids”, approximately 90% of
the fibers of the CST cross over to the other side
of the (“decussate”); that’s why, the left hemisphere
of the brain controls the right side and
vice versa.