Lecture 7: Neuranatomy of White Matter Flashcards
What is the white matter composed of?
Axons of the neurons
It appears white because of the myeline
How is the white matter organized?
- It is organized in bundles of fasciculi:
- Commissural fibres
- Projection fibres
- Association fibres
- Each fasciculus has a name and is associated with a function depending on what it connects
- Not random
- As the brain develops, some connections are formed and some removed
What are the commissural fibres?
- Connection between the hemispheres
- Commissural fibres:
- Corpus callosum
- Anterior commissure
- Posterior commissure
- Hippocampal commissure
The Corpus Callosum
- Largest commissural bundle
- Divided into 7 parts:
- Rostrum
- Genu
- Rostral Body
- Anterior Mid-body
- Posterior Mid-body
- Isthmus
- Splenium
What does the Rostrum in the CC connect to?
- Orbitofrontal areas
- Pre-frontal areas
What does the Genu in the CC connect to?
- Obitofrontal areas
- Pre-frontal areas
What does the Rostral Body in the CC connect to?
- Premotor and Supplementary motor areas
What does the Anterior Mid-Body in the CC connect to?
- Sensori-motor areas
What does the Posterior Mid-Body in the CC connect to?
- Parietal Areas
What does the Isthmus in the CC connect to?
- Posterior Parietal
- Superior Temporal
What does the Splenium in the CC connect to?
- Occipital area
- Inferior Temporal areas
The Anterior Commissure
- AC
- Connects areas of the temporal cortex to the subcortical structures (amygdala) and olfactory bulbs
What are association fibres?
- Fibres connecting different areas of the brain within a same hemisphere
- Intra-hemispheric
- Association fibres:
- Superior Longitudinal Fasciculus (SLF)
- Middle Longitudinal Fasciculus (MLF)
- Inferior Longitudinal Fasciculus (ILF)
- Fronto-Temporal Extreme Capsule Fasciculus
- Arcuate Fasciculus
- Uncinate Fasciculus
- Inferior Fronto-Occipital Fasciculus (IFOF)
Superior Longitudinal Fasciculus
- 3 branches: Purple, Green and Orange
- Parietal to Frontal areas
Arcuate Fasciculus
- Yellow
- Frontal and posterior Temporal areas
Middle Longitudinal Fasciculus
- Light Blue
- Parietal to Temporal
Fronto-temporal Extreme Capsule Fasciculus
- Purple
- Frontal to anterior-mid temporal areas
Uncinate Fasciculus
- yellow
- Orbitofrontal to anterior temporal areas
Inferior Longitudinal Fasciculus
- green
- Occipito-temporal connections
Inferior Fronto-occipital Fasciculus
IFOF
- red
- Occipito-frontal connections
What are Projection Fibres?
- Connection between cortex and subcortical structures
- Projection fibres:
- External capsule
- Interior capsule
External Capsule
- Motor cortex to putamen
- unidirectional
Internal Capsule
- Cortex to subcortical structures
- Massive white matter highway
- bidirectional
In the spinal cord which are the tracts that consists of white matter?
- Descending tract (motor pathway)
- Ascending tract (sensory pathway)
