- Cerebral White Matter 289
Commissures & Disconnections ( Advanced )
■ C o m m i s s u r a l fi bers connect corresponding areas
of the cerebrum; the two main commissural
bundles are the anterior commissure and the corpus
callosum.
■ Th e corpus callosum lies superior to the anterior
commissure and connects dorsal cortical areas,
whereas the anterior commissure connects ventral
areas.
■ Th e anterior commissure connects the bilateral
ventral posterior frontal lobes and also the bilateral
anterior temporal lobes.
■ Th e corpus callosum connects the bilateral
hemispheres from the frontal to the occipital poles.
■ Th e anterior-inferior portion of the corpus callosum
is the rostrum; the anterior-superior portion is the
genu; the length of the corpus callosum is the body;
and the posterior portion is the splenium.
■ In alexia without agraphia, there is injury to the
medial left posterior occipital lobe and also to the
right visual projection fi bers aft er they have crossed
midline within the splenium of the corpus callosum.
■ Alien hand syndrome has three forms: the callosal
variant, which manifests with intermanual confl ict;
the frontal variant, which manifests with involuntary
grasping ; and the sensory variant, which manifests
with limb ataxia.