<P> It is the main product of the embryonic diencephalon, as first assigned by Wilhelm His, Sr. in 1893 . </P> <P> The thalamus is a paired structure of grey matter located in the forebrain which is superior to the midbrain, near the center of the brain, with nerve fibers projecting out to the cerebral cortex in all directions . The medial surface of the thalamus constitutes the upper part of the lateral wall of the third ventricle, and is connected to the corresponding surface of the opposite thalamus by a flattened gray band, the interthalamic adhesion . The lateral part of the thalamus is the phylogenetically newest part of the thalamus (neothalamus), and includes the lateral nuclei, the pulvinar and the geniculate bodies . There are areas of white matter in the thalamus including the stratum zonale that covers the dorsal surface, and the external and internal medullary laminae . The external lamina covers the lateral surface and the internal lamina divides the nuclei into anterior, medial and lateral groups . </P> <P> The thalamus derives its blood supply from a number of arteries: the polar artery (posterior communicating artery), paramedian thalamic - subthalamic arteries, inferolateral (thalamogeniculate) arteries, and posterior (medial and lateral) choroidal arteries . These are all branches of the posterior cerebral artery . </P> <P> Some people have the artery of Percheron, which is a rare anatomic variation in which a single arterial trunk arises from the posterior cerebral artery to supply both parts of the thalamus . </P>

Which artery supplies the medial surface of the cortex including the hypothalamus
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