tuber cinereum

noun

tuber ci·​ne·​re·​um -si-ˈnir-ē-əm 

: an eminence of gray matter which lies on the lower surface of the brain between the optic tracts and in front of the mammillary bodies and of which the upper surface forms part of the floor of the third ventricle and the lower surface bears the infundibulum to which the pituitary gland is attached