The Catalepsean Node is the 6th of the 19 gene-seed organs that are implanted into a Space Marine Neophyte to produce a new Astartes. This organ is implanted into the back of the cerebrum, just above the brain stem. When deprived of sleep for a long period of time, the Catalepsean Node "cuts in" upon detecting a rise in the Astartes' stress and fatigue hormones. This allows the Astartes to consciously "switch off" sections of the brain sequentially, while remaining awake and alert. This ability comes at a price, as prolonged use of this ability can be hazardous, possibly inducing hallucinations or even psychosis. This implant bears a resemblance to an ancient scientific theory as to how ceteaceans known as "Bottlenose Dolphins" "sleep": shutting off sections of their brain while remaining awake and alert through the active use of the other sections. Yet even the mighty Space Marines cannot go too long without actual rest. The longest any Space Marine has ever been on active combat duty without rest is 328 hours, achieved by a squad of the Crimson Fists' Kill-team during the battle against the Orks for Rynn's World.
- Codex: Space Marines (5th Edition)