NDE or Near-death experience, refers to the experiences reported by people who were nearly dead but luckily resuscitated. They are most commonly shrugged off as existence of soul and afterlife. But, a close examination in scientific perspective, proves us otherwise!
Most common experiences reported are,
- Feeling like going through a tunnel
- Out of Body Experiences
- Intense, pure bright light
- A wonderful feeling of peace
- Seeing spirits and/or communicating with them
Science behind this:
What little research there has been in this field indicates that the experiences typical of the NDE may be due to brain states triggered by cardiac arrest, lack of oxygen, increase of carbondioxide and anesthesia. NDEs are the result of physical changes in a stressed or dying brain.
What we see as “reality” around us is only the sum of all the sensory information our brain is receiving at any given moment.
Going through a Tunnel:
An even more complex system of nerves and muscle fibers allows your brain to know where your body is in relation to the space around it. Close your eyes and raise your right hand until it is level with the top of your head. How do you know where your hand is without looking at it? This sensory system allows you to know where your hand is even when your eyes are closed. Trauma affecting functional areas of the brain, such as the somatosensory and visual cortexes, could cause hallucinations that get interpreted as NDEs. Now imagine that all your senses are malfunctioning. Instead of real sensory input from the world around you, your brain is receiving faulty information, possibly because of drugs, or some form of trauma that is causing your brain to shut down. What you perceive as a real experience is actually your brain trying to interpret this information. Some have theorized that “neural noise,” or an overload of information sent to the brain’s visual cortex, creates an image of a bright light that gradually grows larger. The brain may interpret this as moving down a dark tunnel.
Neural noise and retino-cortical mapping explain the common experience of passage down a tunnel from darkness into a bright light. If you started with very little neural noise and it gradually increased, the effect would be of a light at the center getting larger and larger and hence closer and closer the tunnel would appear to move as the noise levels increased and the central light got larger and larger. If the whole cortex became so noisy that all the cells were firing fast, the whole area would appear light. Neural activity might explain bright lights, buzzing noises, and hallucinations.
Out of Body Experiences (OBEs):
The body’s spatial sense is prone to malfunction during a near-death experience as well. Again, your brain interprets faulty information about where the body is in relation to the space around it. The result is the sensation of leaving the body and flying around the room. Combined with other effects of trauma and oxygen deprivation in the brain (a symptom in many near-death situations), this leads to the overall experience of floating into space while looking down at your own body, and then leaving to float down a tunnel. Using a positron emission tomography (PET) scan, some scientists working in the field showed that the out-of-body experience was related to increased activity in the right temporo-parietal junction, superior temporal, and right precuneal cortices. They suggested that the induced altered spatial self-recognition was mediated by the temporo-parietal junction, which is involved in vestibular-somatosensory integration of body orientation in space.
The experiences of people whose out-of-body adventures allow them to see and hear events that their unconscious body shouldn’t be able to perceive are more difficult to explain. Heightened sensory perception is common in the near-death experience, and a recent study seems to indicate that these feelings of extrasensory perception may be caused by a significant spike in brain activity in the moments just before death. However, it is plausible that unconscious people can still register sensory cues and this coupled with prior knowledge make them incorporate them into their NDE.
Pure, bright light:
A hallucinatory journey to the bright light and beyond, a full-blown NDE, can occur in 20 or 30 seconds, even though it seems to last much longer. During such a crisis, the very concept of time may seem variable or meaningless. And people think they had these experiences for a long, long time because of distorted sense of time.
The feeling among researchers is that the excess CO2 in the bloodstream can have a significant effect on vision, which leads to patients seeing the tunnel and the bright light.
Lack of oxygen to the brain also plays a contributing role. It is well known that oxygen deprivation can lead to hallucinations and may even contribute to the feeling of euphoria that is often reported.
A feel of peace:
The peaceful, calm sensation felt during NDEs may be a coping mechanism triggered by increased levels of endorphins produced in the brain during trauma. It is similar to a lack of emotional response.
Faulty sensory input, oxygen deprivation and endorphin-induced euphoria create a surreal, though realistic, experience. When the subject recalls the encounter later, it has passed through the filter of his conscious mind. Bizarre experiences that seem unexplainable become spirit beings, other dimensions and conversations with God.
A spike in epileptic activity in the temporal lobe may be responsible for the visions of God or of heaven that so many see during a near-death experience. A study devised by Orrin Devinsky enabled him and other researchers to “perform clinical and video EEG monitoring in patients as they are having ecstatic-religious seizures, and thus to observe the precise coinciding of their ‘theophanies’ with seizure activity in temporal lobe foci (nearly always these are right-sided).”
Drug induced NDEs:
Similar experiences can be induced through electrical stimulation of the temporal lobe (and hence of the hippocampus) during neurosurgery for epilepsy, with high carbon dioxide levels (hypercarbia), and in decreased cerebral perfusion resulting in local cerebral hypoxia as in rapid acceleration during training of fighter pilots, or as in hyperventilation followed by Valsalva manoeuvre. Ketamine-induced experiences resulting from blockage of the NMDA receptor, and the role of endorphin, serotonin, and enkephalin have also been mentioned, as have near-death-like experiences after the use of LSD, psilocarpine, and mescaline. These induced experiences can consist of unconsciousness, out-of-body experiences, and perception of light or flashes of recollection from the past. These recollections, however, consist of fragmented and random memories unlike the panoramic life-review that can occur in NDE. Further, transformational processes with changing life-insight and disappearance of fear of death are rarely reported after induced experiences.
NDEs can be induced with ketamine, a short-acting hallucinogenic, dissociative anaesthetic. It can reproduce all the main features of the NDE, including travel through a dark tunnel into the light, the feeling that one is dead, communing with some god, hallucinations, out-of-body experiences, strange noises, etc.
Phew! So, the malfunctioning brain activities might be the possible explanation for NDEs.
And, as always, Mr. Brain wins the cup!
This post is just a compact version of a great explanation by Dr. Krishna Kumari Chella in the above link.