an artery which stems from the internal carotid artery and crosses just ventral to the optic tract to join with the posterior cerebral artery, thereby finishing the arterial circle at the base of the brain. Departments of it provide blood to the optic tract and a portion of the optic chiasm,the posterior hypothalamus, the genu of the corpus callosum, portions of the interior capsule, the third ventricle, and anterior and ventral nuclei of the thalamus.