What happens to our memories when we die?

In the past, it was assumed that brain activity ceases when the heart stops. However, researchers have found that within thirty seconds after death, the brain releases protective chemicals that trigger a short-lived surge of widespread, highly synchronized brain activity that results in intense hallucinations at death. This lasts for at least four to five minutes (according to some studies, for upto seven minutes).

Brain dream death
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A recent study (using mice) demonstrated that brain activity after complete cardiac arrest does not gradually decrease to zero, but is distinguished by bursts of activity in separate phases. This results in hallucinations that are theorized to be the cause of Near Death Experiences (NDEs). When Ketamine (categorized as a “dissociative anesthetic” and horse tranquilizer) is given to people in research studies, a sense of moving through a tunnel, an out-of-body feeling, spiritual awe, visual hallucinations, and intense memories are reproduced.

In fact, at near-death, many known electrical signatures of consciousness exceeded levels found in the waking state, suggesting that the brain is capable of well organized electrical activity during the early stage of clinical death. But death is a process. It’s not a black-or-white line.

A more recent study found that rats show an unexpected pattern of brain activity immediately after cardiac arrest. Although clinically dead (no breath nor heartbeat), for at least thirty seconds their brains showed several signals of conscious thought (the low-gamma waves produced when neurons fire twenty-five to fifty-five times per second) became stronger for a brief period. This suggests that our final journey into permanent unconsciousness may actually involve a brief state of heightened consciousness and memory.

This question originally appeared on Quora ― the place to gain and share knowledge, empowering people to learn from others and better understand the world.