The final moments of the dying process will invariably, involve the stopping of our hearts and lungs, before our brain finally stops working a few seconds afterwards as it stops receiving blood and oxygen. Therefore some scientists have decided to look at this particular time to find the mechanism that may be causing NDEs. They have proposed that as we know that during this final step of the dying process there must be a reduction in brain oxygen levels, because the person stops breathing and the flow of blood to the brain stops, therefore a mechanism involving the effects of reduced oxygen levels may be leading to NDEs, essentially as a complex hallucination. It is thought that in the same way that a drug such as LSD may activate certain parts of the brain and hence lead to the generation of a complex hallucinations, oxygen starvation of the brain may also lead to a similar phenomenon.

One of the main supporters of the role of lack of oxygen in causing at least some aspects of NDE has been Dr Susan Blackmore, who is a former psychologist at The University of West of England. She has proposed an explanation to account for the occurrence of the tunnel phenomenon. Everything that we 'see' is processed in an area of the brain called the visual cortex. The visual cortex is an area found at the back of the brain. When we see something, the light that comes off that object reaches the back of the eye where it is converted into electrical energy and then transmitted to the back of the brain where it is processed (visual cortex). The vast majority of our vision comes from the middle part of our field of vision, with relatively very little coming from the outer fields or peripheral fields. In medical terms this is called central vision which is distinguished from vision that comes from the peripheries, which is called peripheral vision. When we read a book or watch TV, we have to look at it straight on. We can't read a book from the corners of our vision, even though we can still see the pages of a book or the TV screen from the corners of our field of vision. The reason for this is that in our eyes there is an area that is involved with this central vision which has far more specialised cells to process light than the rest of the eye. The brain is also similar in that it too has many more cells and therefore a much larger area devoted to analysing information that comes from the central portion of vision and relatively few devoted to analysing the information that comes from the peripheral portion of vision. It has been suggested that starving the brain of oxygen as occurs at the end of life, may lead to over-activity in the areas of the brain that are responsible for vision. However, as there are far more cells in the brain that are responsible for processing central vision compared with cells responsible for processing peripheral vision, activation of the cells in the back of the brain due to a lack of oxygen will have the effect of creating the illusion of seeing a bright light in the middle. This is due to a relatively higher activation of the cells responsible for central vision compared with those for peripheral vision.