A team of British and American hospital doctors will study the near-death experiences of 1,500 heart attack patients.
The research into 'out of body' experiences is due to take three years and is being coordinated by Southampton University.
Some people who have nearly died report being able to soar out of their bodies and look down on themselves and medical staff.
Doctors will place images on shelves that are only visible from the ceiling. They will see if the patients can recall the images and analyse their brain activity.
Dr Sam Parnia, an expert in the field of consciousness during clinical death who is heading the study, said: 'If you can demonstrate that consciousness continues after the brain switches off, it allows for the possibility that the consciousness is a separate entity.
'It is unlikely that we will find many cases where this happens, but we have to be open-minded.
'And if no one sees the pictures, it shows these experiences are illusions or false memories. This is a mystery that we can now subject to scientific study.'
He added: 'Contrary to popular perception, death is not a specific moment.
'It is a process that begins when the heart stops beating, the lungs stop working and the brain ceases functioning - a medical condition termed cardiac arrest, which from a biological viewpoint is synonymous with clinical death.
'During a cardiac arrest, all three criteria of death are present. There then follows a period of time, which may last from a few seconds to an hour or more, in which emergency medical efforts may succeed in restarting the heart and reversing the dying process.
'What people experience during this period of cardiac arrest provides a unique window of understanding into what we are all likely to experience during the dying process.
Among the British hospitals taking part in the study are Addenbrookes in Cambridge, University Hospital in Birmingham and the Morriston in Swansea.
(Original headline: Doctors to study 'out of body' experiences of 1,500 near-death heart attack patients )
