White Matter Tracks

what are white matter tracks

bundles of myelinated axons that facilitate communication in the brain

what are the three primary white matter tracks

• association fibers

• commissural fibers

• projection fibers

What do association fibers do

connect cortical areas within the same hemisphere

what do commissural fibers do

connect corresponding regions in opposite hemispheres

what do projection fibers do

link the cortex with subcortical structures, brainstem, and spinal cord

what do commissural fibers do

connect corresponding regions in opposite hemispheres

What do short association fibers

connect adjacent gyri (ex. precentral ←>postcentral)

• there’s bundles of white matter btw them

what do the long association fibers do

-connect areas within same hemisphere (expand more than adj. gyri)

what are the long association fibers

• superior longitudinal fasciculus

• inferior longitudinal fasciculus

• inferior fronto-occitial fasciculus

• arcuate fasciculus

• uncinate fasciculus

• cingulum

What does the superior longitudinal fasciculus do

links frontal, parietal, and occipital lobes for spatial awareness, visuomotor coordination, and attention (where)

• link frontal, parietal, and occipital cortex (stream =superior longitudinal fasciculus)

What does the inferior longitudinal fasciculus do

• connects the occipital lobe with the anterior temporal lobe to support semantic (object) processing and object recognition (what)

• connect occipital to temporal

what does the fronto-occipital fasciculus do

• connects orbitofrontal and dorsolateral prefrontal cortex and occipital lobe for visual-cognitive integration for decision making and emotional processing

• process based on visual

what does the arcuate fasciculus do

• connects Broca’s area to wernickes area and supports verbal working memory

what type of aphasia do you get when the arcuate fasciculus is damaged

• Conduction aphasia

• people with this type aphassia with not as many issues producing but naming tasks is hard

ehat does the uncinate fasciculus do?

links Orbitofrontal with anterior temporal pole (memory and emotional regulation)

• sensory info to make decision

what are the commissural fibers

• corpus callosum

• anteiror commissure

• postieror commissure

what is the corpus callosum

• the largest commissural fiber bundle, connecting left and right cerebral hemispheres

  • integration of lateralized functions

  • bimanual coordination

what does the anterior commissure do

• connects the left and right amygdala, ventromedial temoral cortices, and olfactory regions

functions of the anterior commissure

• complex emotional responses

• memory retrieval and description (need both hemispheres to talk to each other to do this

• olfactory perception

what does the posterior commissure do

• plays a role in coordinating bilateral pupillary reflexes

  • example both eyes constricting when doing pupillary light reflex

when the corpus callosum is cut for treatment why is this done?

-could be for epilepsy to prevent seizures propagating to other hemisphere

what is agenesis

-born with no corpus callosum

what are the different projection fibers

-internal capsule

corona radiata

what are the fibers of the internal capsule

• anterior limb

• genu

• posterior limb

• retrolenticular

• sublenticular

what fibers are within the anterior limb

• frontopontine

• thalamocortical fibers

what are the frontopontine fibers

they go to the cerebellum

what do the thalamocortical fibers do

• not sensory

• pathway is cortex→ thalamus→ cortex

what are the fibers of the genu

• corticobulbar fibers

  • c

what are the fibers of the posterior limb

-thalamocortical (sensory)

-corticospinal (motor)

What do the retrolenticular fibers do

-optic radiations

-behind lentiform nucleus

what do sublenticular fibers do

auditory radiations

-under lentiform nucleas

what is the corona radiata

-fan-shaped bundle projecting to and from cortex

what does the corona radiata form

internal capsule

on cross sectional imaging what direction does green represent

-anterior-posterior

on cross sectional imaging what direction is red

left and right

on cross sectional imaging what direction is blue

superior and inferior

microvascular irregularities of degeneration of WM could be

multiple sclerosis

what is DTI

water content

-water moves different from white and gray matter

What does the cingulum do

Interconnects prefrontal and cingulate vortices with limbic areas to support emotional regulation, attention, memory formation and retrieval