Abstracts for the Joint Meeting of Anatomical Societies, 19-22 May 2011, Bursa, Turkey

2011 Anatomy (International Journal of Experimental and Clinical Anatomy)  
The anatomic concept of the hypothalamus changed considerably since its earliest definition. Tridimensional reconstructions, experiments and many staining methods have expanded considerably the number of anatomical details recognized in this territory, probably one of the most complex in the brain. For a long time the predominant anatomic view has interpreted the hypothalamus as a longitudinal column at the floor of the diencephalon, connected rostrally with the telencephalon and caudally with
more » ... he midbrain. However, recent advances in our knowledge of early developmental mechanisms seem increasingly contradictory with this columnar viewpoint. Consideration of early ventralization, dorsalization and anteroposterior patterning effects suggests that, rather than being a diencephalic floor element, the hypothalamus is best understood as a transverse region lying ventral to the telencephalon and rostral to the diencephalon; the latter separates it from the midbrain. A number of gene expression patterns observed in the developing forebrain, part of the emergent genoarchitectonic neuroanatomy, have revealed the true topologic position of the hypothalamus, as well as the nature of its fundamental subdivisions. There are interesting parallelisms with genoarchitectonic patterns in the diencephalon and midbrain. In all these cases continuous longitudinal domains can be distinguished, as well as a number of anteroposterior (transverse) neuromeric units of the neural wall. The hypothalamus has been newly recognized to have two anteroposterior neuromeric subdivisions, named terminal and peduncular hypothalamic portions. These ideas give meaning to the tract trajectories through the hypothalamus and serve to localize more precisely the complex chemical structure and circuitry of this brain region.
doi:10.2399/ana.11.001s fatcat:e6qs7cmzqreejhsdrol7i665c4