Asked by: Lucie Coltman, Via Twitter
Patients in a coma appear unconscious. They do not respond to touch, sound or pain, and cannot be awakened. Their brains often show no signs of the normal sleep-wakefulness cycle, which means they are unlikely to be dreaming. Yet many people who have recovered from comas report dreams into which something of the outside world penetrated. Others recall nightmares that seemed to go on and on.
Whether they dream or not probably depends on the cause of the coma. If the visual cortex is badly damaged, visual dreams will be lost; if the auditory cortex is destroyed, then they will be unable to hear dreamed voices. If the cause is damage to brain areas such as the reticular activating system, which controls the sleep-wakefulness cycle, normal dreams cannot occur but other dream-like states might. The term ‘coma’ covers many conditions. Until we understand them better, it is hard to say which ones can include dreams.