Although there is no actual cathedral near Point Lookout called "Ark & Dove", there is a real Ark and Dove Presbyterian Church further north in Odenton, MD. The "Ark" and the "Dove" were the first two ships that brought settlers to Maryland in 1634.
The partial removal of the brain and the goal of attaining mental peace, references the outdated quackery of lobotomy, where part of the brain was destroyed in an attempt to either make people more easy to care for, or fix mental disorders, but as Nadine alludes, it just caused brain damage. Nadine also says that it's the part of the brain that "holds you back", and a lobotomy can, at least, reduce inhibition (self-control), as well as other normal brain functions.
ps3pcxbox360 When entering the cathedral and talking to Nadine immediately, (and select all of the dialogue options) the cathedral may become locked. As there is no key, this is problematic. This also happens at random if returning to the mainland with Nadine and then returning to the cathedral. [verified]