Just before it ceases functioning, the brain may make a last-ditch effort to find unresolved purpose or a reason to stay alive.

Brain death is rare, though. In New York State, with a population of 20 million, there are on average fewer than 500 cases suitable for organ procurement and transplantation each year.

A pregnant brain-dead woman in Georgia was kept on life support until her fetus was viable. Experts say it raises ethical and legal questions.