[dlorde]

Also. another puzzling thing re those who say consciousness is independent is that consciousness is not there before we become physical beings - and even, some say, in the first few months of life, so how can it leave the body away from the brain processes that create it?

It can't - it is those brain processes; it only exists while they are active.

... perhaps out of body experiences are illusions, just as seeing things 'out there' is an illusion projected out from the brain.

The apparent location, focus, and extent of consciousness (e.g. typically behind the eyes), and the location and sense of ownership of body parts isn't something that just happens as a 'default', it is explicitly constructed from sensory information (touch, proprioception, balance, and predominately vision) in specific areas of the brain. This is known as Mulitsensory Integration. By faking sensory input, it is possible to fool the brain into, for example, thinking an empty rubber glove is one of its hands (the Rubber Hand illusion), or more disturbingly, the location of consciousness is in another body entirely (the Body Transfer illusion).

Disturbances in those areas of the brain, due to drugs, or epileptic seizure, extreme stress, or oxygen deprivation, can lead to spontaneous out of body experiences, or loss of the boundaries of self - a feeling of merging with the universe, and so-on.

[cheryl j]

An interesting debate I stumbled on was between a neurologist and a neuroscientist, the first one who said he had experienced an out of body experience when he was critically ill (Eben Alexander) and came to see it as evidence of the after life, and the second (Sam Harris) who was skeptical that his experience in any way supported the idea that consciousness can exist separate from the neural mechanisms of the brain.

Alexander says: "Isolated preservation of cortical regions might have explained some elements of my experience, but certainly not the overall odyssey of rich experiential tapestry. The severity of my meningitis and its refractoriness to therapy for a week should have eliminated all but the most rudimentary of conscious experiences: peripheral white blood cell [WBC] count over 27,000 per mm3, 31 percent bands with toxic granulations, CSF WBC count over 4,300 per mm3, CSF glucose down to 1.0 mg/dl (normally 60-80, may drop down to ~ 20 in severe meningitis), CSF protein 1,340 mg/dl, diffuse meningeal involvement and widespread blurring of the gray-white junction, diffuse edema, with associated brain abnormalities revealed on my enhanced CT scan, and neurological exams showing severe alterations in cortical function (from posturing to no response to noxious stimuli, florid papilledema, and dysfunction of extraocular motility [no doll's eyes, pupils fixed], indicative of brainstem damage).  Going from symptom onset to coma within 3 hours is a very dire prognostic sign, conferring 90% mortality at the very beginning, which only worsened over the week. No physician who knows anything about meningitis will just “blow off” the fact that I was deathly ill in every sense of the word, and that my neocortex was absolutely hammered. Anyone who simply concludes that “since I did so well I could not have been that sick” is begging the question, and knows nothing whatsoever about severe bacterial meningitis."

Harris responds: "[Alexander] doesn’t understand what would constitute compelling evidence of cortical inactivity. The proof he offers is either fallacious (CT scans do not detect brain activity) or irrelevant (it does not matter, even slightly, that his form of meningitis was “astronomically rare”)—and no combination of fallacy and irrelevancy adds up to sound science. The impediment to taking Alexander’s claims seriously can be simply stated: There is absolutely no reason to believe that his cerebral cortex was inactive at the time he had his experience of the afterlife. The fact that Alexander thinks he has demonstrated otherwise—by continually emphasizing how sick he was, the infrequency of E. coli meningitis, and the ugliness of his initial CT scan—suggests a deliberate disregard of the most plausible interpretation of his experience. It is far more likely that some of his cortex was functioning, despite the profundity of his illness...."

I would tend to agree with Harris over all, but the fact that some patients can have rather complex experiences or memories (hallucinatory or not) when large areas of the brain would seem to be suppressed by anesthetic, deprived of glucose, or severely compromised in other ways, does raise interesting questions about how consciousness is distributed across the brain or emerges.

[dlorde]

I would tend to agree with Harris over all, but the fact that some patients can have rather complex experiences or memories (hallucinatory or not) when large areas of the brain would seem to be suppressed by anesthetic, deprived of glucose, or severely compromised in other ways, does raise interesting questions about how consciousness is distributed across the brain or emerges.

Yes, I've read Alexander's account, and it does seem to make rather a lot of unsupported assumptions about the circumstances of his reported experiences - and an uncritical acceptance of the accuracy of his memories of them. I wondered why he assumed these experiences and the memories of them occurred when his brain was at its most minimally functional, and not during his extended recovery. For example, without being seriously ill, I've personally had dreams that probably lasted less than an hour, but which on recall, seemed to encompass days of complex narrative. Dream experience seems to occur in sequences and snapshots, cut together in memory like a film and eliding the time between them. Episodic memory is known to be reconstructive, and confabulatory detail is commonplace.

It struck me that perhaps the emotional impact of Alexander's experience had overridden his capacity to think critically about it.

[cheryl j]

Yes, I've read Alexander's account, and it does seem to make rather a lot of unsupported assumptions about the circumstances of his reported experiences - and an uncritical acceptance of the accuracy of his memories of them. I wondered why he assumed these experiences and the memories of them occurred when his brain was at its most minimally functional, and not during his extended recovery. For example, without being seriously ill, I've personally had dreams that probably lasted less than an hour, but which on recall, seemed to encompass days of complex narrative. Dream experience seems to occur in sequences and snapshots, cut together in memory like a film and eliding the time between them. Episodic memory is known to be reconstructive, and confabulatory detail is commonplace.

Yes I wondered about the time frame as well, whether his experiences and memories occurred late in recovery or were reconstructed very shortly after. Often in dreams, an outside noise or a phone ringing, will fit into the dream narrative perfectly, in a way that makes me wonder if my brain didn't quickly revise the story, and my memory of it, to explain it.   There are also experiments with normal people where the brain reorders or back dates events in time, such as observing that a blue light flashed before a red one, when it in fact came after.

It struck me that perhaps the emotional impact of Alexander's experience had overridden his capacity to think critically about it.

That was kind of the impression that I got as well.
[/quote]

[buawangji]

for everyone you meet is fighting a harder battle.

[annie123 (OP)]

Just read a book by Michio Kaku - the Future of the Mind (2013) in which his definition of consciousness is:Consciousness is the process of creating a model of the world using multiple feedback loops in various parameters (e.g. in temperature, space, time, and in relation to others) in order to accomplish a goal (e.g.finding mates, food shelter)- the "space-time theory of consciousness".
In the book there is a section on out of body experiences which gives the best explanation of this phenomena that I have come across so far. A Dr. Olaf Blanke of Switzerland purport to have located the precise place in the brain that generates out of body experiences. By stimulating a specific area of the  brain, these experiences can be turned on, and off if the stimulus was removed. This is the temporalparietal area. "This is further explained by evidence that when messages form the eyes and inner ear are disrupted electrically at the boundary of the temporal and parietal lobes the brain gets confused about its location in space. Also temporary loss of blood or oxygen or excess carbon dioxide in the blood can also cause a disruption in the tempo parietal region and induce out of body experiences which may explain the prevalence of these sensations during accidents, emergencies, heart attacks etc."
Re the tunnel effect some experience when approaching death, this may be because the blood flow to the eye is decreasing and peripheral vision is the first to be affected.
This book is worth reading.

[dlorde]

Thanks for that, Annie - it seems to fit pretty well with what I've read elsewhere. Fighter pilots have regularly reported the tunnel effect (often with bright light) training to withstand high 'g' in the centrifuge, when approaching G-force induced loss of consciousness (G-LOC).