Perspicacity (3.5e Feat)
From D&D Wiki
 Perspicacity [General]
Your mental acumen keeps you from losing your concentration.
You may use your Intelligence modifier when making Concentration checks instead of your Constitution modifier.
If you are ever forced to make a Concentration check because of a mind-affecting effect, you must use your Constitution modifier for the check as normal. For example, a wizard with Intelligence 17 and Constitution 12 attempting to maintain a spell after taking 3 points of Intelligence damage from a touch of Idiocy spell makes the check with his Constitution bonus (+1) in stead of his (modified) Intelligence bonus (+2).