posterior perforated substance posterior perforated substance the depressed area between the crura is termed the interpeduncular fossa, and consists of a layer of gray matter, the posterior perforated substance, which is pierced by small apertures for the transmission of blood vessels; its lower part lies on the ventral aspect of the medial portions of the tegmenta, and contains a nucleus named the interpeduncular ganglion; its upper part assists in forming the floor of the third ventricle. posterior perforated substancecoronal section of brain immediately in front of pons. (post. perf. substance labeled at lower left.)detailsidentifierslatinsubstantia perforata posterior, substantia perforata interpeduncularisneuronames1580anatomical terms of neuroanatomy