Corpus callosum embryology can be divided into three parts: during ''c
ommissuration'', a cellular mass develops between two telencephalic ve
sicles. The primitive lamina terminalis corresponds to the closing poi
nt of the anterior neuropore. Its dorsal part grows and forms the lami
na reuniens (6-8 intra uterine weeks, IUW). From ventral to dorsal, th
is lamina reuniens gives rise to the area praecommissuralis (origin of
the anterior commissure), to the primordium hippocampi (10 I.U.W., fo
rnix), and to the massa commissuralis (10 S.I.U., corpus callosum). Fi
bers arising from the developing hemispheres run through this primitiv
e corpus callosum. The growth of the corpus callosum follows the expan
sion of the hemispheres, in a rostro-caudal and then dorso-ventral cir
cular movement. The last part of the corpus callosum to form is the ro
strum. Maturation occurs postnatally, and corresponds to axomal elimin
ation, and myelination, progressively changing the callosal connection
pattern of the newborn and infant into the adult pattern.