“But unlike dreams, (Near Death Experiences) NDEs tend to feature some specific images, such as seeing a tunnel with a light at the end.
The tunnel actually has nothing to do with the NDE – it’s to do with what’s happening to your vision. During fainting, for instance, there’s a blackout because the eye isn’t getting enough blood, so the eye begins to shut down even though the brain is still going. As it shuts down first from the sides and then into the centre, it’s like looking through a tunnel.
The light that people tend to see has a few sources. To start with, the eye might only be capable of seeing smudges of light because of the tunnelling and lack of blood flow. Then, as the brain enters REM consciousness, the visual system becomes strongly activated – that’s the rapid eye movement that defines REM consciousness. When the visual system is activated, you get light.
People often report having out- of-body experiences during NDEs.
These come about because the temporoparietal region of the brain is turned off, so the brain is no longer able to map the body’s position in space. A Swiss researcher named Olaf Blanke was able to use electrodes to turn the temporoparietal region of a woman’s brain on and off, making her feel like she was floating up out of her body and then returning. It was like flipping a light switch.
REM consciousness turns the temporoparietal region off, so if you are semi-conscious in a borderland between waking and REM, you can easily have an out- of-body experience. These are extremely common during lucid dreams, narcolepsy, fainting and sleep paralysis – all borderland states. I have never had one, though. I wish I could!”