The first one is a music Easter Egg. First, in the room that has a picture of a dog (hellhound) and human (zombie), there are two brains in containers: one on a cart next to the stairs with the debris, and the other on a shelf right across it. Hold square (or X on the X-Box 360) on them. The one on the shelf, you'll have to jump and press square/X and jump again and press square/X. The last brain is in the places where one of the Teleporters are. Go into the room where you can buy a Steilhandgrate of the chalkboard, hold square. After the while you'll here music, and "Beauty of Annihlation" plays.