Prethalamus

The prethalamus (formerly described as ventral thalamus) or subthalamus is part of the diencephalon and therefore part of the brain.

Developmental biologist prefer the term prethalamus, as it can be genetically defined (Puelles and Rubenstein, 2003), whereas (human) anatomists often use the expression subthalamus.

The prethalamus is part of the mid-diencephalic territory (MDT) containning also the zona limitans intrathalamica (ZLI), and the thalamus. Caudally, the prethalamus is separated from the thalamus by the ZLI acting as lineage restriction boundary. The pro-neural gene Dlx2 serves a typical marker of the prethalamus. Typical nuclei of the prethalamus are the zona incerta, thalamic reticular nucleus, and the fields of Forel.

The prethalamus is patterned by Sonic hedgehog signalling from the ZLI. Anatomically, it develops efferent (output) connections to the striatum (caudate nucleus and putamen) in the telencephalon, to the thalamus (medial and lateral nuclear groups) in the diencephalon, and to the red nucleus and substantia nigra in the mesencephalon. It receives afferent (input) connections from the substantia nigra and striatum.