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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).

For the Thalamic nuclei, a new subdivision based on Hirai T, Jones EG (1989 A new parcellation of the human thalamus on the basis of histochemical staining. Brain Res Rev 14:1-34) and updated by Morel A, Magnin M, Jeanmonod D (1997 Multiarchitectonic and stereotactic atlas of the human thalamus. J Comp Neurol 387:618-677) is used to replace the list of terms in TA (14.1.08.603-14.1.08.658), largely a matter of a more practical grouping of nuclei. As Latin synonym the term Regio is adopted from Percheron G (2004 Thalamus. In: Paxinos G, Mai JK, eds: The Human Nervous System, 2nd ed. Elsevier, Amsterdam, pp 592-675).

The basal parts of the prosomeres P1-P3 form several nuclei, previously included in the Mesencephalon (see General footnote). The rostral parts of the Substantia nigra/VTA-complex also derive from P1-P3. The term Tegmentum prerubrale is preferred as topographic term over Tegmentum diencephali.