Hindbrain

The hindbrain was the secondary brain of the Ood. It was generally carried in the hands. When the Ood were enslaved by the Earth Empire, the hindbrain was removed and replaced with a translation orb. (TV: Planet of the Ood) This limited the Ood's telepathic abilities to Basic 30 and made them servile. (TV: The Impossible Planet / The Satan Pit)

Before the time where his hindbrain would typically be removed, Brian was bought by the Lesser Order of Oberon. They then cut his hindbrain themselves in a dark basement, quickly and roughly, which made Brian obedient, but not docile. (AUDIO: The Minds of Magnox)