White matter anatomy

Question 1

White matter

Answer 1

The CNS is comprised of white and grey matter. The white matter is essentially cabling linking one part to another. In places these cables are aggregated to form distinct bundles.

Question 2

There are three types of white matter cables

Answer 2

Projection tracts, comissural tracts, association tracts

Question 3

Projection tracts

Answer 3

ConnectionsConnect higher centers of the brain (those beyond the brain stem) with lower centers (e.g. brainstem and spinal cord)

Question 4

Commissural tracts

Answer 4

ConnectionsConnect the two hemispheres together

Question 5

Association tracts

Answer 5

ConnectionsConnect regions of the same hemisphere. Long association connect separate lodes together whereas short association fibers connect separate gyri of the same lobe

Question 6

Tract type- projection

Answer 6

ExamplesCorticospinal
DescriptionEfferent projection fibers that connect motor cortex to the brain stem and spinal cord

ExamplesCorticobulbar
DescriptionEfferent projection fibers that connect motor cortex to the brain stem and spinal cord

ExamplesCorona Radiata
DescriptionFibers to and from virtually all cortical areas fan out superolaterally from the internal capsule

ExamplesInternal Capsule
DescriptionMajor conduit of fibers to and from the cerebral cortex

ExamplesGeniculocalcarine Tract (optic radiation)
DescriptionConnects the lateral geniculate nucleus to occipital (primary visual) cortex

Question 7

Tract type- commissural

Answer 7

ExamplesCorpus Callosum
DescriptionThe largest white matter fiber bundle, the corpus callosum is a massive accumulation of fibers connecting corresponding areas of cortex between the hemispheres

ExamplesAnterior Commissure
DescriptionThe anterior commissure crosses through the lamina terminalis. Its anterior fibers connect the olfactory bulbs and nuclei; its posterior fibers connect middle and inferior temporal gyri

Question 8

Tract type-association

Answer 8

ExamplesCingulum
DescriptionInterconnects portions of the frontal, parietal, and temporal lobes

ExamplesSuperior Occipitofrontal Fasciculus
DescriptionConnects occipital and frontal lobes

ExamplesInferior Occipitofrontal Fasciculus
DescriptionConnects the occipital and frontal lobes

ExamplesUncinate Fasciculus
DescriptionConnects the orbital and inferior frontal gyri of the frontal lobe to the anterior temporal lobe

ExamplesSuperior Longitudinal (arcuate) Fasciculus
DescriptionConnects the frontal lobe cortex to parietal, temporal, and occipital lobe cortices (the largest association bundle)

ExamplesInferior Longitudinal (occipitotemporal) Fasciculus
DescriptionConnects temporal and occipital lobe cortices