Psychoactive extraction was the process of extracting an entire mind from a being, not making a copy of it but actually depriving them of the original.
Skagra's sphere, created by the scientists he had gathered at the Think Tank before he used the finished result to absorb their own minds, was capable of psychoactive extraction. He hoped to use the sphere on the Time Lord Salyavin and thereby absorb his unique psychic power to transfer his own mind into other people's, so that the sphere could both absorb and transfer minds, and thereby be used by him to transform himself into a Universal Mind. This scheme was foiled by the Doctor, who readily recognised the sphere's function as psychoactive extraction when he encountered it. (WC: Shada, AUDIO: Shada, PROSE: Shada, TV: Shada)
The Greth later considered absorbing Azacca Dixon to absorb Az's psychic powers, thinking to itself about possibly gaining the ability to "graft [its] thoughts into every living thing [it] encountered" if it could combine "psychoactive extraction" with "mental transmogrification". However, this did not come to pass either. (PROSE: Out of the Box)