Internal configuration – white matter

White matter

Corpus callosum

  • Arch-shaped bridge of white matter between the two cerebral hemispheres
  • Front end: rostrum, behind and underneath the genu of the corpus callosum
  • Back end: splenium
  • Anterior angles: forceps minor
  • Posterior angles: bundle of fibres, divided into two parts:
    • Lateral part: tapetum, contributes to form the superior and lateral walls of the inferior and posterior horns of the lateral ventricle
    • Medial part: forceps major

Septum pellucidum

  • Thin median and sagittal membrane
  • Separates the anterior horns of the lateral ventricles
  • Underneath the corpus callosum and above the fornix

Fornix

  • Double cord of fibres above the thalami, underneath the corpus callosum
  • Forms part of the roof of the third ventricle
  • Three parts:
    • Crus of fornix
      - Fibres from the alveus form the fimbria, then the crus of fornix
      - It converges medially and unites with the contralateral crus of fornix while adhering to the inferior surface or the corpus callosum
    • Body of fornix
      - Linked to the contralateral body of fornix by the commissure of fornix
    • Column
      - Splits off from the contralateral column and contributes to form the interventricular foramen
      - Extends into the mamillary body

Anterior commissure

  • Thin cord that connects together the ventral parts of the cerebral hemispheres
  • Enables interconnections between the temporal lobes (cortex and amygdaloid bodies)
  • Contains fibres of the medial olfactory stria stemming from the olfactory tracts

Posterior commissure

  • Thin bundle of fibres
  • Allows pretectal interconnections
  • Contains habenulotectal fibres

Internal capsule

  • Large conduction band that wanders along between the thalamus and the lenticular nucleus
  • Three sub-sections:
    • Anterior limb
    • Genu
    • Posterior limb
  • Downward and laterally-oriented
  • Extends into the cerebral peduncles