After a lot of back-and-forth, it's unclear what source from which this card originated. It is not mentioned in Kaplan, UWorld, or Khan Academy and is not mentioned in AAMC guidelines.

Further complicating the issue is that the Cisternal Maturation model has changed over the years, and different biology textbooks cover and mention different, sometimes contradictory, aspects of the model. No mention of the term is made in any primary sources.

In light of the contradictions, a lack of evidence of primary support for its being testable information, and ongoing confusing related to the content of the card, I'm proposing that it be culled from the deck.