Consciousness remains a mystery

Dr. Sam Parnia writes: “For millennia, defining death was easy and straightforward. Nobody needed to worry about what was life and what was death. It was quite clear and obvious: when a person’s heart stopped, he or she was dead. It was known that people would die for two main reasons—either their hearts stopped or they stopped breathing. Whichever stopped first (the heart or the lungs) would cause the other organ to also stop quickly, and then the brain would also stop working almost immediately afterward; therefore, we could say someone was dead.

“Scientists were not aware of a period of time after death in which the organs and cells in the body remained viable and had not yet become irreparably damaged, and hence death could be reversed. We were also not aware of the fairly long time that existed between these two states. The other way that death could happen was if someone has severe trauma to the brain; in that case, the brain would swell up and then start to press on the brain stem, which is where the reflexes are located that regulate the heartbeat and breathing. If the brain stem is compressed, all the nerves there stop working and the person immediately stops breathing and the heart immediately stops beating.

“But now the advances in medicine indicated that for the first time in history, death had to be defined in some other completely different way. This would enable the definition of death to also include the point in time where there is irreversible brain damage irrespective of whether the heart is still beating—brain death—to accommodate the growing number of people who could now be kept alive artificially (by maintaining their heartbeats and breathing) even after they had developed permanent brain death.

“Anything that impacts the ability of brain cells to be active will cause the brain to stop functioning. This includes when someone’s blood sugar has dropped to very low levels, or if the temperature in the body is very low. Certain drugs, particularly those given for sedation and anesthesia, will also stop brain activity if given in high enough doses.

“There are case reports of people who had appeared to be brain dead (and had met all the brain death testing criteria) after being examined many hours and days after being warmed up to a normal temperature following hypothermia treatment for cardiac arrest. Only to show signs of brain recovery up to seven days later.

Consciousness, Parnia asserts, remains a mystery. “It is not like understanding the science of cell functions, or for that matter any other entity we have studied in the physical sciences in the past. Though it is a pure mystery, we know it exists and defines who we are. Nonetheless, nobody has been able to explain how human consciousness comes to be.

“As a consequence of the progress in resuscitation science that started in earnest almost half a century ago and has been evolving since, over the past forty years there has been growing recognition that people who have had a close brush with death or have gone beyond the threshold of death and entered the gray zone that exists between death and permanent irreversible brain damage have provided consistent mental recollections that correspond with that period. 

Sam Parnia, Erasing Death: The Science That is Rewriting the Boundaries Between Life and Death (HarperOne, 2013), 264-284.