Type two, involving the right hemisphere, is characterised by seeing or communicating with spirits, and hearing voices, sounds and music.
While it’s unclear why there are different types of near-death experiences, the different interactions between brain regions produce these distinct experiences.
The temporal lobes also play an important role in near-death experiences.
This area of the brain is involved with processing sensory information and memory, so abnormal activity in these lobes can produce strange sensations and perceptions.
Despite several theories used to explain near-death experiences, getting to the bottom of what causes them is difficult.
Religious people believe near-death experiences provide evidence for life after death – in particular, the separation of the spirit from the body.
Whereas scientific explanations for near-death experiences include depersonalisation, which is a sense of being detached from your body.
Scientific author Carl Sagan even suggested that the stress of death produces a remembrance of birth, suggesting the “tunnel” people see is a reimagining of the birth canal.
But due to the fanciful nature of these theories, other explanations have emerged. Some researchers claim that endorphins released during stressful events may produce something like near-death experience, particularly by reducing pain and increasing pleasant sensations.
Similarly, anaesthetics such as ketamine can simulate near-death experience characteristics, such as out-of-body experiences.
Other theories suggest near-death experiences arise from dimethyltryptamine (DMT), a psychedelic drug that occurs naturally in some plants.
Rick Strassman, a professor of psychiatry, observed in a study from 1990 to 1995 that people had near-death and mystical experiences following injection of DMT.
According to Strassman, the body has natural DMT released at birth and death. However, there is no conclusive evidence to support this view.