Gray Matters

 is a perk found in the data files of the Fallout 3 add-on Point Lookout. It doesn't appear in the game and can only be obtained with console commands.

Behind the scenes
The term grey (or gray) matter is used for one of the two major components of the central nervous system (along with white matter).

The perk may have been associated with the Lump of Brain obtained from the Duchess Gambit engine room after dealing with Tobar.

The perk may also have been associated with A meeting of the minds. Maybe there was the possibility to side with the brain, and instead of him killing you, it may have been cut content to gain this perk if you help out Calvert and kill Desmond