Some mediums have a history of concussion or similar early in their lives. My friend is psychic and she had an accident as a child. A part of her left temporal lobe is sending out bursts of signals that are not compatible with being awake (theta waves), while the rest of the brain is awake and she is awake. This is seen as a type of epilepsy. But it sort of goes hand in hand with the article. The area of her brain is less, not more active.