Telencephalon

As they grow, the hemispheres envelop the lateral ventricle. Each of the two lateral ventricles is connected to the 3rd ventricle by an interventricular foramen, which initially is a relatively large opening. The hemispheres have two different components: a thick basal part, which is the primordium of the ventricular eminence and an anti-basal part with thin walls called the pallium. The ventricular eminence is subdivided by the intereminential sulcus into a medial part (S14) and a lateral part (from S15). Nuclei originating from the diencephalon form the medial part (medial ventricular eminence),: some of these remain in the diencephalon and some later move into the telencephalon, e.g. the globus pallidus and parts of the amygdaloid body. Basal telencephalic nuclei form the lateral part (lateral ventricular eminence). These are the corpus striatum (caudate nucleus and putamen), parts of the amygdaloid body, the nucleus basalis and the claustrum.
The pallium differentiates into the cerebral cortex (cortex cerebri) and the white matter (substantia alba), composed of nerve cell axons. Differentiation of the wall of the hemispheres initially is similar to that of the rest of the neural tube. However, it is later supplemented by the formation of a cortical plate; this is the origin of most of the cerebral cortex.