A stroke that robbed a 73-year-old woman of her dreams helpede pinpoint where and how dreams are born in the brain. The stuff that dreams are made of is a chunk of grey matter deep down at the back of the human brain. The back half of the brain, which is involved in the visual processing of faces and landmarks.

Soon after her stroke, the woman reported a peculiar and incredibly vivid hallucination or dream. She was not sure whether she was awake or asleep, says Claudio Bassetti, a neurologist who documented her case. After that, she lost the ability to dream completely for about three months. This suggests that hallucinations and dreaming have the same origin, says Bassetti.

'How dreams are generated, and what purpose they might serve, are completely open questions at this point,' said Bassetti.

'These results describe for the first time in detail the extent of lesion necessary to produce loss of dreaming in the absence of other neurological deficits. As such, they offer a target for further study of the localisation of dreaming,' added Bassetti, who led the study.

Not surprisingly, the 73-year-old woman also lost some of her vision. That came back but then her dreams disappeared.

They studied the patient's brain waves as she slept and found no disruptions in her sleep cycle.

The woman has recovered some ability to dream, but they are less vivid, the researchers said.

'Further conclusions about this brain area and its role in dreams will require more studies analysing dream changes in patients with brain damage,' said Bassetti.

This study proves that dreams are not essential to life.