Some of these experiences are very personal, but I think this is an important topic that needs to be discussed by believers and non-believers alike, so I will include at least some of the details. I happen to not believe in a soul, an afterlife, spirits, the supernatural, free will, or an autonomous, essential self, but I have had experiences similar to NDEs and other encounters, and this gives me a unique perspective. If anyone wishes to know more or share similar experiences, I'm always interested, so send me a private message. I will try not to be too personal in these thoughts, but I find these experiences relevant to my search for the truth about the nature of such phenomena.
I have not had an NDE, but I have read many accounts of them over the years and have studied them. I have also had experiences that included aspects of NDEs, such as out of body experiences, dreams of dying and leaving the body and encountering vivid, beautiful places where I talk with loving people about my life and where I am in relation to it. I've had extremely vivid dreams my entire life, especially in childhood, and I've also encountered telepathic beings full of the most extraordinary love and understanding and compassion I have ever felt. I encountered them when I was struggling with coming to terms with being gay, and I saw my whole life through their eyes and how all love is beautiful, even for someone of the same sex. They knew every imperfection and wrongdoing, but there was no judgment, only complete and total acceptance and love. I've also found myself in the midst of a dream when all of the images melted away and all that was left was a point of consciousness flying in a beautiful, dark void. I felt more conscious in this state than in waking life and it felt like I had existed in this state before, that I had flown and danced that way in the void but had forgotten it. I was immersed in euphoria.
But I do not believe that NDEs or similar experiences, including my own, or indicative of anything supernatural. Near Death Experiences: In or Out of the Body is one of the best books I've read attempting to provide a scientific theory to explain NDEs. Suggesting a soul that interacts with the brain creates the problem of an immaterial entity interacting with a material one. NDEs do have striking similarities, but the most common seem to be a product of our nervous system and brain structure, which does a fine job of explaining the similarities.
For instance, the tunnel and light can be explained by noise in the visual cortex. This has been simulated by Blackmore with a computer model; with gradually increasing noise in the visual cortex, a light in the center will appear to grow, thus creating the simulation of moving through a tunnel.
Interestingly, Blackmore herself has had an NDE, but it was drug induced. This makes sense if activity in the brain creates the apparent experience.
Temporal lobe epilepsy also often results in NDE-like experiences and is associated with heightened religiosity. Some temporal lobe epileptics will become obsessed with religion and practicing it, and they have a heightened response in the brain to religious words and imagery in comparison to control groups.
Various other triggers exist for NDEs and religious experiences as well, including mental illness, artificial gravity, etc.
This site lists various triggers with links to articles. The site embraces a supernatural interpretation of NDEs, but still has much useful information and NDE accounts.
Some scientific studies suggest that altered temporal lobe functioning might be characteristic of people who have had NDEs, although this may have resulted after the NDEs.
It may be that people who experience NDEs are "physiologically distinct from the general population:"
While accounts abound about those who can see objects during an NDE out of body experience (or astral projection), they are anecdotal and there is no substantial evidence that even people experienced in inducing out of body experiences are able to report sights accurately significantly above chance levels.
The temporal lobe is involved in religious experience and can be stimulated to create spiritual experiences. There is some evidence suggesting that we all have varying levels of temporal lobe instability. Those with more instability may be more prone to having mystical or religious experiences, which might explain why some people are hyper-religious or have spontaneous mystical experiences.
These experiences can also occur in relation to schizophrenia and bi polar disorder. I am diagnosed as a schizo-affective and have exhibited symptoms of this disorder since my early childhood and have a history of mental illness in both sides of my family. It is important to recognize that mental illness can in some cases be related to producing these experiences. Just as drugs may sometimes inspire insight -- not always, but in some cases -- mental illness may sometimes do the same.
Bi polar disorder, for instance, may be related to creativity.
However, they shouldn't be brushed away as insignificant. These experiences can provide deep insights and healing for years of pain. In one instantaneous, spontaneous, completely unexpected encounter with the Love all of the self-hatred I had learned from abuse because of my sexual orientation instantly disappeared, and I have never again rejected or shamed myself for loving other men. Shortly afterward, I was outed by someone who found out and rejected by my family, but I have known since that experience that there is nothing wrong with me, and I never hide who I am.
The evidence suggests that these experiences are natural, physical phenomena, but I think insights can be obtained from these altered states about the nature of consciousness and the way our brains construct reality. They are not by any means proof of spirits, a soul, or an afterlife, but they should not be brushed aside by skeptics as containing no glimmer of truth, either.