It’s a fascinating topic to me. I got introduced to this fact as an argument for an afterlife, but I’m more interested in the biological aspect. What happens in the brain?
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It doesn’t function in the way you may think. It’s just the neurons (the cells of the brain) slowly suffocating. I am an electroneurodiagnostic technologist and I’ve done brain death studies and I’ve had people on EEG (a test that looks at your brain waves) while they passed away. You’re brain communicates to itself and your body through electrical impulses. So when you are dying and your heart is no longer pumping blood to your brain, your brain waves slow down like when you are asleep but they drop in amplitude so they are very flat and then they stop completely. It’s just because your organs don’t die right when your heart stops beating. They die when your heart stops supplying them oxygenated blood.
Your body doesn’t have an off-switch. It’s a system of many parts, and they don’t all stop functioning at once. Depending on the cause of death, circulation to the brain may be cut off, and that will eventually cause the brain cells to die, but not immediately. The cells have some oxygen and energy left to burn, but when they run out, it’s game over.
So it all depends on how you define “death”, which is not as straightforward as you might think. Even if you make it synonymous with brain death, the brain doesn’t necessarily die all at once. You could suffer damage to the cortex that leaves you unconscious and unable to interact with your environment, but with an intact brainstem that keeps your body’s vital functions going.
In any case, if you define death as the brain ceasing to function (irreversibly), then the brain by definition does not continue to function after death. If you define death as the irreversible cessation of circulatory and respiratory functions (e.g. if your heart has permanently stopped beating), then obviously that leaves some leeway for the brain to stay alive, though not for long if it isn’t supplied with oxygen some other way.
There’s no mystery here and it’s not an argument for an afterlife. The brain still stops functioning, even if brain death comes some time after the death of other body parts. If you think that brain functioning is necessary for an afterlife, you’re obviously out of luck. If you think that a short period of brain functioning after your other organs have died allows some kind of “transition” to an afterlife, then I put it to you that this transition could also start to happen before the rest of your body starts to die (if such wondrous things are possible, getting the timing right seems trivial in comparison), so the case for such a transition isn’t strengthened by the observation that the brain sometimes keeps functioning after (say) the heart has stopped beating – just as it isn’t weakened by the observation that this doesn’t always happen. The brain may sometimes be the first part of a person to die, e.g. if they suffer a fatal stroke or get shot in the head, so then this period does not occur.
In other words, if you want to believe in an afterlife, that’s your prerogative, but you can’t use this period of residual brain function as evidence one way or another.
If you think about the experiments done during the French revolution when executing people with guiliotines these are not considered scientifically valid as the results do not match later experiments. These were probably conducted under heavy confirmation bias causing people to see and interpret things that was not the case.
What we do know today is that death is not an instantaneous process. It is a rather long chain of events where each cell and each organ fails progressively. The brain do have an instantaneous “off” switch which makes you unconscious in traumatic events in order to conserve as much oxygen and energy as possible. This does usually trigger early on in the death process. But it is still possible to wake someone up from this condition as long as blood flow is maintained so some oxygen gets to the brain. This is why CPR is so important. If the neurons is starved for oxygen they will eventually die, cell by cell. This can trigger nearby neurons and cause some apparent neurotic activity. The same is true for the neurons in the spine and out to each muscle. Even dead bodies can have muscle spasms.
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