Flashcards in Bales: White matter systems Deck (17):
What is a radiation?
A "radiation" is usually a projection from a more localized area to a broader area
For example, both auditory and visual systems have radiations
What are commissures and decussations?
Tracts connecting the same structures or areas are usually called “commissures”
Tracts connecting different structures or areas are usually alled “decussations”
What do short fascicle interconnect?
close cortical regions
can be called "arcuate" or "U" fibers
What connects Broca and Wernicke's areas? What would a lesion in this region cause?
a lesion here would cause a conduction aphasia
What does the inferior longitudinal fasciculus connect?
occipital and temporal lobes
What connects the anterior temporal and the lower frontal lobes?
the uncinate fasciculus
What does the anterior commissure connect?
The anterior temporal lobes
What is the function of the corpus callosum? What parts of the corpus callosum are larger?
corpus callosum fibers interconnect similar areas in opposite hemispheres
the rostral and caudal ends are larger in area because they accommodate more fibers (forceps minor (anterior) and major (posterior))
Where is there more likely to be a dysgenesis of corpus callosum and why?
the splenium will always be affected because the corpus callosum develops from front to back
What will result from a full callostomy?
Normally, visual info from the right occipital lobe (left visual field) gets to Broca’s on left via corpus callosum. Without splenium, patient can’t read aloud words in left visual field.
the splenium is normally spared when preforming a callostomy for intractable epileptic seizures to avoid this
What is the corona radiata? What is its name when it passes between large gray meter nuclei? What is it continuous with inferiorly?
fibers to and from cortex and lower (subcortical) structures (e.g., thalamus, brainstem, and spinal cord)
between the lentiform nucleus and the thalamus and caudate nucleus, it is called internal capsule
inferiorly, the internal capsule is continuous with the crus cerebri (of the cerebral peduncle of the midbrain)
What structures encapsulate the lentiform nucleus?
the external (laterally) and internal capsule (medially)
What are the layers surrounding the lentiform nucleus on the lateral side before it reaches the insula?
medial to lateral:
What does the centrum semiovale contain fibers from?
the internal capsule, callosal fibers and the superior longitudinal fasciculus
When does myelination start and end?
starts prenatally and finishes after the 2nd year
sensory (dorsal) myelinate ahead of motor (ventral) in the spinal cord and projection is myelinated before association pathways
the spinal cord myelinates before the brainstem
brainstem myelinated caudal--> rostral
after 2 y.o, the U-fibers and association cortices are still myelinated
What will the T2 MRI differences be in a 1 week old vs a 2 year old? Why is that?
The 1 week old will have hyperintense white matter
after myelination, the 2 year old will have mature white matter which is hypointense relative to gray (it will have more darkness on the MRI)
myelination reduces the relative water content of white matter (by increasing the lipid content) --> water shows up more white on an MRI