Neuroscience in relation has its roots in the late 1800s around the time Charles Darwin's theory of evolution was becoming more widely accepted. Various groups formed with the goal of researching spiritual claims of mediums and others.
Today brain science continues and many books chronicle medical observations of near death experiences (NDEs) and theorizing connections - or lack of connections - with potential evidence for an afterlife. Although science acknowledges the reality of the reported experiences, the jury is still out that it is evidence of a connection with an afterlife or contact with another world.
Out of body experiences, entering a tunnel and proceeding towards a light and seeing loved ones are common in NDEs, as are feelings of joy, overwhelming love and a loss of fear. Despite the commonalities and reality of the experiences, neuroscience explains the experiences as being biological, relating to the brain and its altered states of consciousness rather than being related to an afterlife.
So much of the body can cease functioning and still life - or spirit - remains. Irrevocable death can only come with death of the brainstem. Ultimately, regardless of the disease or injury, it is a break in oxygen supply that causes death of the brainstem. The impact of oxygen starvation on the brain correlates with the arising of NDEs, their interpretation personalized within religions and cultures, yet with the common elements that can be tied to biological events in the brain.
Today there are two camps in neuroscience - those that believe NDEs are purely physiological and psychological events and those that believe them to have a possible transcendental meaning. If there is a spiritual realm, then there must be something like a soul that can exist separate from the body. If that is true, the biological symptoms should be independent from the NDEs, but they are not. And yet, what is the soul, if it exists? Does it provide animation and personality to the body? If so, it must be connected to the material body. And around it goes.
Fundamentalists interpret their religion's scriptures literally. Although applicable to strict adherence in any belief, fundamentalism is found particularly in some followers of Protestant Christianity or Islam. Thus, beliefs in fundamentalist followers will be that of their ideological writings. Mainstream Protestant beliefs can be less certain and more varied, in comparison to their fundamentalist counterparts who have very rigid beliefs. Orthodox religious interpretations of Heaven and Hell have a fair amount of diversity.
For instance, fundamentalist Mormon polygamy sects believe that men must have at least three wives to become High Priest Apostles to become a god in the afterlife. He will rule over his own planet in the afterlife, populated by his perpetually pregnant wives and their children.