A healthy brain has activity in the ceberal cortex, the part of your brain that controls cognative brain function, talking, seeing, thinking, ect. However a brain in a vegetable state there is little to no activity in this part of the brain. However there is activity in the part of the brain that controls breathing and other sub cognative activities. Therefore a person in a vegetable state is unable to understand anything and is little more than a machine that is being kept running