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Libelle of note

The Diencephalon in its classic, columnar view was divided into four dorsoventrally arranged columns separated by ventricular sulci: the Epithalamus, the Dorsal thalamus, the Ventral thalamus and the Hypothalamus. Extensive embryological studies made it clear that the thalamic 'columns' are derived from transversely oriented zones, the Prosomeres (see TE). Currently, the (Caudal) Diencephalon is subdivided into three segmental units, which from caudal to rostral, contain in their alar domains the Pretectum (prosomere 1 or P1), the Epithalamus and the Thalamus (P2) and the Ventral thalamus or Prethalamus (P3). The diencephalic basal plate contains the rostral part of the Substantia nigra-VTA complex and some other nuclei, collectively forming the Diencephalic or Prerubral tegmentum between the Mesencephalon and the Hypothalamus. The entire Hypothalamus or Rostral diencephalon arises from the alar and basal components of the secondary prosencephalon. The Preoptic area is one of the subpallial developmental domains (Puelles L, Harrison M, Paxinos G, Watson C 2013 A developmental ontology for the mammalian brain based on the prosomeric model. Trends Neurosci 36:570-578).

The brain stem is composed of the midbrain (mesencephalon) and the hindbrain (rhombencephalon). The hindbrain was traditionally divided into the metencephalon (pons and cerebellum) and the myelencephalon or medulla oblongata. During development, the brain stem is segmentally organized. The midbrain is derived from two mesomeres, the isthmus from the isthmic rhombomere (rhombomere 0), and the hindbrain is composed of 11 rhombomeres. The cerebellum arises from the alar plates of the rhombomeres 0 and 1. The rostral hindbrain is derived from the rhombomeres 0 to 6, whereas the caudal hindbrain is derived from the rhombomeres 7 to 11.