These theories are all based upon the well-established fact that changes in the amounts of some of the chemicals or neurotransmitters in the brain can lead to 'abnormal' and disordered thought processes, or in other words a hallucination. Many scientists have debated which parts of the brain are involved in NDEs and have theorized that they may be due to brain cell activity in the limbic or temporal lobes. What we do know is that each area of the brain processes multiple functions and that 'conscious' states such as seeing, thinking, feelings and emotions are mediated in many areas at the same time. When someone is about to die, the body initially responds by releasing certain chemicals and steroids to try and maintain the blood pressure and allow sufficient blood to get to the brain. After a while, however, the blood pressure drops and there is thus reduced blood flow to the brain, which will in turn activate certain parts of the brain and lead to the near death experience. Although we still do not know exactly which areas are involved, undoubtedly brain processes do mediate the experience. But the discovery of the exact areas will not explain the significance of near death experiences. Neither will it make a near death experience 'unreal' or a hallucination, in exactly the same way that discovering the areas of the brain involved in viewing pictures or experiencing maternal love doesn't make those sights or feelings hallucinations. This is because all human experience is mediated through different processes of the brain, whether they are commonly understood experiences such as love or anger, or less commonly understood ones such as near death experiences.

For a fuller explanation please refer to neurology and near death experience.

In this section some of the commonly proposed mechanisms to account for NDE are explained.