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.

Protect what is important. With the ability brains, damage to your head will be reduced by 25%.

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.