Newsweek published a cover story by Eben Alexander, a neurosurgeon who claims to have visited heaven while in a coma resulting from bacterial meningitis. Religious believers have predictably jumped all over the story as proof that their beliefs are correct, that we have a soul that is entirely separate from the body and that after we die that soul continues on to the afterlife. Sam Harris throws some cold water on that argument:
Everything—absolutely everything—in Alexander’s account rests on repeated assertions that his visions of heaven occurred while his cerebral cortex was “shut down,” “inactivated,” “completely shut down,” “totally offline,” and “stunned to complete inactivity.” The evidence he provides for this claim is not only inadequate—it suggests that he doesn’t know anything about the relevant brain science. Perhaps he has saved a more persuasive account for his book—though now that I’ve listened to an hour-long interview with him online, I very much doubt it. In his Newsweek article, Alexander asserts that the cessation of cortical activity was “clear from the severity and duration of my meningitis, and from the global cortical involvement documented by CT scans and neurological examinations.” To his editors, this presumably sounded like neuroscience.
The problem, however, is that “CT scans and neurological examinations” can’t determine neuronal inactivity—in the cortex or anywhere else. And Alexander makes no reference to functional data that might have been acquired by fMRI, PET, or EEG—nor does he seem to realize that only this sort of evidence could support his case.
This poetic interpretation of his experience is not supported by evidence of any kind. As you correctly point out, coma does not equate to “inactivation of the cerebral cortex” or “higher-order brain functions totally offline” or “neurons of [my] cortex stunned into complete inactivity”. These describe brain death, a one hundred percent lethal condition…
We are not privy to his EEG records, but high alpha activity is common in coma. Also common is “flat” EEG. The EEG can appear flat even in the presence of high activity, when that activity is not synchronous. For example, the EEG flattens in regions involved in direct task processing. This phenomenon is known as event-related desynchronization (hundreds of references)…
There are many reports of people remembering dream-like states while in medical coma. They lack consistency, of course, but there is nothing particularly unique in Dr. Alexander’s unfortunate episode.
There is much more to Harris’ article, including comparing the reported experiences of Alexander to nearly identical reports from those who use psychadelic drugs. The lesson is clear: Alter the physical and chemical properties of the brain and you can produce a staggering variety of memories and experiences that never actually happened. This is evidence for a non-dualist conception of consciousness, not a religious one.