Time brain

The Time Brain was a giant brain created by the Rani. By using the minds of geniuses from across time and space, the Rani planned to use the brain to do the calculations needed to create a Time Manipulator with which she could reshape the universe to her liking. One of the items on her agenda was to revert Earth to the age of the dinosaurs so that they could realise their full potential. Her plans were stopped when the Seventh Doctors' brain was added, stopping the Rani from controlling it.

Individuals used to create the Time Brain included Albert Einstein, Louis Pasteur, and Hypatia. (TV: Time and the Rani)

Behind the scenes
In Dimensions in Time the Seventh Doctor uses "time brain" to describe the brain of a Time Lord. Although this is not canon, Time Lord brains are known to have a greater understanding of time, possibly revealing that the Rani was trying to create a time lord-like brain.