We have always been told there is no recovery from persistent vegetative state - doctors can only make a sufferer's last days as painless as possible. But is that really the truth? Across three continents, severely brain-damaged patients are awake and talking after taking ... a sleeping pill. Brain-damaged patients are reporting remarkable improvements after taking a pill that should make them fall asleep but that, instead, appears to be waking up cells in their brains that were thought to have been dead. No one yet knows exactly how a sleeping pill could wake up the seemingly dead brain cells, but [researchers] have a hypothesis. After the brain has suffered severe trauma, a chemical known as Gaba (gamma amino butyric acid) closes down brain functions in order to conserve energy and help cells survive. However, in such a long-term dormant state, the receptors in the brain cells that respond to Gaba become hypersensitive, and as Gaba is a depressant, it causes a persistent vegetative state. It is thought that during this process the receptors are in some way changed or deformed so that they respond to zolpidem differently from normal receptors, thus breaking the hold of Gaba. This could mean that instead of sending patients to sleep as usual, it makes dormant areas of the brain function again and some comatose patients wake up.