The latest video for AI: The Somnium Files gives us a good look at the in 'Mental Lock' component of the Somnium portions of the game.
In the Somnium part of gameplay, you go into the world of dreams for key characters. While in dreams, you'll have to clear various obstacles known as “Mental Locks” to find all the clues. Mental Locks prevent you from accessing certain parts of the mind and memories of a person. You'll have to carefully examine things, then solve mysteries by making choices to get past these Mental Locks.