DB is a 67-year-old man whose view of the world is dark from the center of his gaze leftward. He has been blind to this left part of his visual scene since age 33, when he had surgery to remove an abnormal tangle of blood vessels at the back of his brain. Unfortunately, while taking out the tangle, surgeons destroyed an important center of visual processing called the primary visual cortex, or area V1, which relays information from the eyes to higher-level brain areas dedicated to sight.