Levinius V was a planet located somewhere in the space of the galaxy's Alpha or Beta Quadrants, the fifth planet in orbit of the Levinius star system. In the 21st century, the population of Levinius V experienced an outbreak of mass insanity. In the year 2267, the crew of the Federation starship USS Enterprise concluded that this was caused by blastoneurons, a type of neural parasite. (TOS episode & Star Trek 2 novelization: Operation -- Annihilate!; TOS - Operation: Annihilate comic: "Part 1")