The neurological basis of near-death experiences remains a bit of a mystery, despite a number of theories. The main problem is that death is, of course, a one-way ticket. Then there is the problem that death is not a precise event – it tends to be a steady process during which the normally highly-regulated functions of the body gradually degrade.
And yet despite these problems there do seem to be characteristic features of the experience – bright lights, feelings of well being, and out of body experiences – that tend to be reported by people who have been close to death. Many of these sensations can be triggered in healthy people. Out-of body experiences can be induced by tricking the senses, as well as by directly stimulating the brain. What’s more, many of the hallucinatory experiences reported can be induced using ketamine, which blocks a neurotransmitter called glutamate. And here’s where it gets interesting.
A Dutch cardiologist has suggested that near-death experiences are in fact related to hibernation. Hibernating animals protect their brain cells by decreasing the number of receptors for glutamate. This stops them going into a kind of toxic spasm as the oxygen levels drop.
Perhaps, when close to death, the human brain goes into a state similar to hibernation. Maybe this explains the hallucinations, and also the disinhibition of memories (your life flashing before your eyes).
C. van Tellingen (2008). Heaven can wait – or down to earth in real time Neth Heart J, 16 (10), 359-362 Full text on PubMed Central