As described in the Talk, the adolescent human brain is undergoing significant change. This PBS article describes adolescent brains as "works in progress." In this slideshow, you can see the brain's changes throughout human life.
Still interested in the human brain? Watch the 8 fascinating videos in the TED talk playlist, "How does my brain work?" You can also see images of normal and diseased brains at the Whole Brain Atlas and get loads of information and pictures of all types of mammalian brains at the Brain Museum.