Neuroscience of near-death experience

 

“Volunteers undergoing intravenous ketamine infusions (an anesthetic molecularly similar to the street drug PCP or angel dust), frequently experience a profound clarity of thought . One subject described "a sense of understanding everything, of knowing how the universe works." Such descriptions are quite similar to those who've had "near-death experiences" from a cardiac arrest or an anesthetic complication ; indeed, there may be a common mechanism of action. Lack of adequate brain oxygen characteristically triggers the release of the neurotransmitter glutamate. Under normal conditions glutamate binds to NMDA receptors ; in excessive amounts it is neurotoxic and facilitates neuronal death. In an attempt to prevent this cell death, the oxygen-deprived brain also releases protective chemicals that block the effect of glutamate on NMDA receptors . Ketamine has a similar NMDA receptor-blocking effect. So does MDMA (Ecstasy) , another psy­choactive drug known to produce feelings of mental clarity. It is now believed that this blocking of the NMDA receptor is responsible for the clinical picture of a near-death experience . “