It is sometimes claimed that as long as we are mortal humans we can know nothing about an afterlife. This agnostic claim is based on the idea that an afterlife can never affect earthly life, and this position can only be correct if all the evidence for conscious survival, postmortem communication, and reincarnation were best explained by the workings of the minds of the living. I certainly do not believe this to be the case, but I will limit myself here to the question whether the survival of consciousness during a flat EEG has any implications for consciousness after death.
Consciousness without an active cortex
Unless we prefer to embrace the less parsimonious hypothesis of retrocognition (ESP concerning events in the past), some NDEs certainly appear to indicate that consciousness may survive clinical death when the brain shows a flat EEG-pattern. This is simply denied by dogmatic skeptics, but the evidence is growing. Now, some critics claim that consciousness without an active cortex to support it implies nothing about the possibility of consciousness after death. In other words, we may know that consciousness very probably survives a flat EEG, but we should still remain completely agnostic about consciousness after the brain is destroyed. Is this a reasonable position?
Possible objections to the extrapolation from consciousness during flat EEG to brain death
Let us consider what types of objections may be raised against the extrapolation from consciousness during a flat EEG to possible post-mortem consciousness. (I distinguish between clinical death as a state that is in principle physically reversible and brain death as a state that would be irreversible. If these terms are not medically correct, the reader should replace them by the right terms.)
(1). Irreversible brain death is physiologically different from brain inactivity
It is obvious that irreversible brain death is physiologically different from a temporary clinical death after which the brain's activity is resumed. However, why should this be a relevant difference in this context? We are dealing exclusively here with the functional cessation of brain activity as such, not with any precise mechanisms behind this cessation or with the question whether the cessation is temporary or final. The relevant part concerns the supposed brain processes embodying or supporting consciousness. It is irrelevant whether these processes in the brain will be reactivated again or not.
I can think of only one type of physiological difference that might in theory be relevant. This is that during clinical death there could still be some physiological activity deeper in the brain that would vicariously support consciousness, which is normally connected to the cortex. However, there is no evidence that it is plausible that such non-cortical brain processes could support enhanced consciousness as reported during NDEs. Thus far we have no reason to believe in the relevance of processes deeper inside the brain during clinical death.
I am aware that NDE-researcher Melvin Morsesupports the idea that "deep temporal lobe and associated limbic structures mediate the experience and that memory and perception of consciousness do not depend on function[al] cortical structures". I am not aware, though, of any actual empirical evidence that activity in those structures seems to be specifically linked to consciousness. If the theory were correct, there should be heightened, unusual activity in such brain areas in NDEs during a flat EEG, because those areas would presumably take over cortical functions. Until such data would be found, the theory remains purely speculative and, furthermore, implausible from a general neuropsychological perspective that specifically connects enhanced consciousness to cortical functioning. Note that we are not talking about primitive forms of consciousness, but about full-blown, lucid human consciousness that includes 'higher order' thought, memory and volition. It is not to be expected that non-cortical parts of the brain could suddenly take over supposedly highly complex functions of the cortex during clinical death. This would require an instant reorganisation of the brain that from an orthodox neuropsychological point of view may be plausible in infants while the cerebral structures are still developing but not in an older child or adult and never instantly.
Results from artificial stimulation of certain brain areas during experiments designed to emulate NDEs may only be significant for this issue if the stimulation is accompanied by a flat EEG. It is not enough that the limbic structure or deep temporal lobe are stimulated, they should produce enhanced consciousness while the cortex shows no activity measurable by an EEG. Unless this is demonstrated by empirical evidence, Pim van Lommel is right to dismiss the theory of residual brain activity as an explanation for conscious awareness in NDEs during clinical death.
Moreover, Peter Fenwick has recently stated the following during his Bruce Greyson Lecture in 2004: "The flat electroencephalogram (EEG), indicating no brain activity during cardiac arrest, and the high incidence of brain damage afterwards both point to the conclusion that the unconsciousness in cardiac arrest is total. You cannot argue that there are ‘‘bits’’ of the brain that are functioning; there are not."
All this is also relevant for the theory that during the flat EEG there would still be enough activity in the cortex itself. Though I accept that some simple or low-levelled cognitive activity comparable to associative dreaming might still be accounted for by residual cortical processes, this is a far cry from believing that such processes might actually explain the level of thought, memory, emotion and perception shown in NDEs.
Furthermore, in one well documented case of a paranormal NDE, that of Pam Reynolds, the very surgical procedure ensured that there was no measurable brain activity whatsoever. If we take this case seriously, we have to admit that no area of her brain (nor her brain taken as a whole) could have been sufficiently active to account for her NDE. Even if her paranormal perception of surgical preparations were not accompanied by a flat EEG, the rest of her NDE took place while she was brain-dead in the broadest possible sense. Her neurosurgeon Dr. Spetzler, admitted that he could not explain her experiences by normal mechanisms.
(2). Consciousness uses residual brain energy during clinical death
This paper has implications for the value of my article The Survivalist Interpretation of Recent Studies into the Near-Death Experience
See also: Medical Evidence for NDEs by Dr. Pim van Lommel.
The Shadow of Death by Dr. Michael B. Sabom.
Near-Death Experiences and Ouf of the Body Experiences
Near Death Experiences in Cardiac Arrest and the Mystery of Consciousness by Dr. Sam Parnia.
Veridical Perception During NDEs by Janice Holden and Jeffrey Long
Who's afraid of life after death? by Neil Grossman
Science and Spirituality: A Challenge for the 21st Century, by Peter Fenwick
About the Continuity of Our Consciousness, by Pim van Lommel