Quoted from my Own book on these phenomenon (keep in mind OBEs and NDEs are essentially similar / possibly the same experience, just initiated by different means). I'm the author of the below, and it covers some of the physiological theories behind OBEs/NDEs and my counter to some of them. There is also a great article by a Lawyer called a Lawyer's Argument for the afterlife which gets into much of the same... including an experiment by Dutch scientists which seems to prove that something exists beyond physical death and can be measured.
Theories On The Out-Of-Body Experience
Common OBE theories can be divided into two groups... those that
believe something leaves the physical body during an OBE, and those
that believe nothing leaves the physical body and that the OBE is
purely physiological in nature. Here are some of the more common
theories:
The Consciousness Separates And Leaves The Physical Body -
To believe in this theory, we need to look at consciousness as
separate from the physical brain. Consciousness controls the brain
but is not a product of it. We all know that fields can exist around a
physical object like a magnet, even though we can not easily see
them. Consciousness can be thought of a field that extends far past
the physical brain, and uses the physical brain to interact with the
physical world.
Quantum physics theories actually allow for this possible explanation.
If consciousness exists separate from the brain, then it must be able
to leave the physical brain for periods of time. Quantum mechanics
allows for multiple dimensions, accounting where consciousness
might travel during an OBE.
We do not know all that there is to know with our current scientific
knowledge, and I believe that quantum physics is only beginning to
open the door to understanding phenomena like out-of-body
experiences. I believe that ultimately, it will be able to be proven by
science. We have just not gotten there yet.
Most major religions believe in a multidimensional universe, or that
this physical life is only one step our existence as spiritual beings.
Therefore, most people on the planet already believe in a life after
death of some sort. And if the belief of a world beyond the physical
exists in so many minds, then it should not be much of a step further
to believe that we can access the realms beyond this one while still in
this life, through meditation and prayer.
---
Nothing Leaves The Physical Body;
Physiological Theories For OBEs:
I have a friend who is currently studying for his specialty in neurology
(a self proclaimed skeptic), and he was able to explain to me some of
the medical theories behind OBEs.
The OBE Is A Result Of Dissociation / Dislocation -
Dissociative phenomena are experienced as a disruption of the
normally integrated functions of memory, identity perception and
consciousness. This results in a feeling of separateness and in some
cases people reported seeing their physical body from a different
perspective. Dissociation and/or dislocation usually happen as a result
of a traumatic event, stress, or sleep deprivation. It is also linked to
Multiple Personality Disorder.
Dissociation may account for some OBE-like phenomena that happen
from an awake state, but do not explain those instances where an
OBE happened to patients during general anesthesia, or NDEs (Near
Death Experiences) where the person is clinically dead, for all intents
and purposes unconscious and unable to consciously experience the
dissociative phenomena.
Some neurologists would argue that the act of the brain dying, can
stimulate certain parts of the brain, and this may account for the
imagery.
The OBE Is Just A Dream -
The majority of OBEs happen spontaneously from within a sleep
state. This suggests that OBEs could really be vivid dreams or dreams
where one has become aware, called Lucid Dreaming, which will be
covered later in this book.
Evidence from experiments by Charles Tart in the 1960’s, have
shown that OBEs do not occur within a discrete measurable state,
and instead can happen in a variety of different states. Subjects that
successfully projected out-of-body while hooked up to an EEG
(electroencephalogram, where electrodes placed on the head can
measure brainwave activity) in Tart’s laboratory were shown to have
had their experience during periods of deep relaxation, heightened
awareness, but not exclusively during REM (Rapid Eye Movement)
sleep, which is when most dreams occur.
Also of note, are the OBEs that people have reported while being
under general anesthesia, and seeing the surgeon working on them as
they floated above the operating table. General anesthesia is known
to suppress REM sleep.
Dreams are commonly believed to be Astral Projections, where we
are not aware that we are projecting. Tart’s experiments only
conclude that an OBE can occur in many states. That does not mean
that REM can not be one of those states. It does however suggest
that not all OBEs occur during a state where we are dreaming.
The OBE Is A Hypnapompic/Hypnagogic Hallucination -
Some people with a sleep disorder such as narcolepsy, sometimes
experience vivid imagery just as they are falling asleep or upon
waking. Another symptom of narcolepsy is sleep paralysis, where the
person wakes up unable to move for a brief period. These symptoms
are caused by elements of REM sleep intruding on the waking state.
However, people who do not have narcolepsy can also experience
both sleep paralysis and hypnagogic or hypnapompic hallucinations.
It has been suggested that OBEs could just be vivid imagery from
these hallucinations.
This theory could explain some of the OBE experiences, but since
Tart found that REM sleep does not necessarily have anything to do
with OBEs, and the fact that OBEs have occurred while people have
been under general anesthesia when they are most definitely not
waking up and experiencing hallucinations, it can not account for all
of the OBE type phenomena.
Also of note, is that with hypnapomic and hypnagogic hallucinations,
the imagery can be very different from person to person and very
dream-like in quality. Common images are vague shapes and
shadows that may already be in the room but are changed in the
mind of person having the hallucination to resemble something else.
I find it hard to believe that an OBE could be a hallucination because
for everyone who experiences it, the circumstances are exactly the
same, except for the location where they are projecting. The sounds
and feelings experienced in an OBE do not seem to change much
between individuals. And Instead of having dreamlike imagery, an
OBE seems to fall on the opposite side of the spectrum, almost being
too real to be a fantasy created by the mind.
Sleep paralysis does play a role however, and is related to OBEs.
Many people report that they were in sleep paralysis immediately
prior to an OBE. It is from the paralysis state that the required
vibrations seem to develop. All though not all people report having
sleep paralysis episodes before their OBEs, it may just be that they
were unaware of the paralysis. Deep relaxation is definitely
necessary to induce an OBE, so maybe the complete body paralysis
(which is relaxation at its utmost) allows an OBE to happen more
easily.
I have had numerous OBEs occur in conjunction with sleep paralysis
episodes, where I would wake up unable to move anything but my
eyes, and then immediately feel strong vibrations and hear rushing
sounds in my ears. I think that when someone is in sleep paralysis,
they may already be half way out-of-body.
The Angular Gyrus, and Epilepsy –
As described by CNN news on 19 September 2002, Neurology
researchers in Switzerland reported that during a procedure for
epilepsy, a patient told them she had floated above her own body and
was watching herself. This happened when a particular part of the
brain called the angular gyrus, in the right cortex, was stimulated by
an electrode… and it happened every time the angular gyrus was
stimulated.
The explanation is that OBEs could be caused by a misfiring of
certain parts of the brain while under stress. The angular gyrus is
thought to have a role in how the brain analyzes sensory information.
Of course, certain parts of the brain may indeed play a role in OBEs.
I have no doubts that something physiological needs to happen to
induce the consciousness to separate, and that maybe the angular
gyrus is part of the equation. Where our consciousness goes when it
separates, the scientists can not account for! In all the years of
neuroscience, they have yet to be able to pinpoint the exact point of
consciousness in our brains!