First things first: if you really want to know what happens to your brain when you die, you're going to need to abandon your squeamishness at the door. What I'm about to write here is necessary, important and has, in the case of medical donation and research, saved many thousands of lives — but it's not very cute to read about. So leave your gag reflex behind.
Most peoples' thoughts about the journey their brain undergoes after death center around the idea of near-death experiences, or whether the brain can keep going after the heart has stopped. But that is, for the great majority of us, only the beginning. After we die, our brains pass into the care of professionals who treat it with great respect, but who also may use it in various ways — and then, ultimately, it passes into the hands of nature or a crematory fire. It is dead tissue, but it was once the most crucial part of a human being, and for that reason it can go through quite a set of loops and roundabouts before being laid to rest.
Depending on your choices and those of your family and carers, your brain may be donated to science, sent out for autopsy, or simply injected with solutions for funeral preparation — and none of those options are particularly pretty or un-gruesome in practise.
So gear up, stay calm, and enjoy learning about one of the most interesting things that will ever happen to your body: death.
1. One Last Big Surge In Brain Waves
This big discovery was hailed in 2013 as the real big cause of "near-death experiences." It seems that, just after we die, a gigantic spike happens in brain activity. It's very, very brief, and it's only been observed in rats (because tests performed on dying humans are obviously hard to get past the ethics committee). But it's the sort of brain activity we'd expect to see in conscious, thinking humans — humans who are not just awake, but alert and contemplating something. Essentially, you may "wake up" extremely briefly after death — using a large amount of the neural connections depicted in the image above, which was generated by researchers at Brown University to depict the ways our brains function.
The study, from the University of Michigan, has been characterized as explaining why people who have had serious heart-related difficulties — the kind where blood flow to the brain ceases entirely— seem to experience moments of incredibly clear perception after the point where their brains should have ceased functioning. The cause may not be entirely clear, but it's somewhat comforting to think that our brains may give us one last, very real sense of experience before we go.
2. Brainstem Tests For Donated Brains
Once you have shuffled off this mortal coil, pushed up the daisies, gone to God, and been declared clinically, irrevocably dead, the brain's afterlife in medicine may actually just be beginning. It all depends on your particular situation in death, as well as your wishes as to what happens to your body afterwards.
If you're donating organs, the first step any clinician takes is to check your brainstem activity. Tests include shining flashlights in eyes and placing tubes down the windpipe, in order to see if the brain creates any natural bodily response. There are also a lot of scanning tests that can be done to confirm the diagnosis, like MRIs, EEGs (testing for electrical activity in the brain), sonography and nuclear brain scanning. Basically, doctors make damn sure the brainstem is completely without activity before they do anything with it.
3. Brain Removal For Brains Undergoing A Postmortem
If you happen to die in a way that clinicians or your family thinks warrants a postmortem, the process won't look as pretty as it does on television (and it already doesn't look very pretty on television). Postmortems are generally done to diagnose a whole-body cause of death, but the doctors doing the diagnosing do as much as possible to avoid damaging the face, in case the family would like an open-casket funeral. To that end, a brain being examined in a postmortem is accessed through an incision in the back of the skull, which is not visible from the front.
It's first examined inside the skull, and then gently removed for further tests. And yes, they do need to take the whole thing: taking a small sliver won't give doctors a full picture of what happened, which tends to be the problem with diagnosing from biopsies (small bits of tissue taken from living people).
Oddly enough, when doctors take cell tissue cultures from brains within an eight hour window immediately following death, those tissues can be kept "alive" (in very small batches) for a few weeks. That doesn't mean your brain still works, though; the cells respond to stimuli, but they've been sliced out of the brain in exceptionally thin parts and carefully put in a petri dish, so they don't engage in any real neural functioning.
4. Neuropathological Examinations For Brains Given To Science
If you've donated your brain to a scientific institution for study, scientists will be cutting it up — but what they're looking for depends very much on how you died. For instance, if you had dementia when you passed away, they'll examine the hippocampus, midbrain and various other parts of the brain that are specifically linked to that diagnosis. Neuropathological exams aren't one-size-fits-all, and neuropathologists in the US have to be highly qualified.
Interestingly, it may not be possible to donate your brain to one particular scientific institution and your body to another. Many medical research schools and anatomy centers — where most donated bodies end up— like the entire body to be intact. If you really want your brain sent to one specific institution and your body to another, you'll have to find specific centers who'll accept this sort of arrangement.
5. Injection Of Formaldehyde For Funerals
Most bodies in funeral homes tend to be prepared the same way, even if they're going to be cremated rather than buried. The body is injected with the preservative formaldehyde in a hidden place, either under the armpit or in the groin. The formaldehyde is then pumped into all areas of the body, including the brain. (Funeral home workers will increase the amount of formaldehyde pumped in if the body has to be transported a long way to the funeral.)
Formaldehyde is undergoing a bit of a backlash in other arenas of brain-preservation, though. It's been discovered that if you want to actually use a brain that's got formaldehyde in it for anything later on, like a science experiment, your results may be a bit skewed. In 2013, scientists found that laboratory brains that had been preserved in formaldehyde gave up unreliable results during a variety of medical procedures, including autopsies. Why? It turns out formaldehyde messes up the amount of cellular water in the brain — and cellular water is a crucial element in diagnosing various problems with the brain after death. Whoops.
If you're being cremated, your brain, like the rest of your body, will burn and become ash (usually the entire body is gone within 90 minutes). However, if you're going to be buried, it will decompose in the soil — but there are some interesting variants as to how fast this actually happens, depending on when and how you're buried.
Buried bodies have been embalmed, but their rate of decomposition depends on how close to the surface, and to water, they are. If you've been buried shallowly (within two feet of the surface), your entire body will decompose and become a skeleton within 18 months to three years. This is actually illegal; law dictates that you have to be buried under at least six feet of ground. In that case, the decomposition process is far slower, particularly because the coffin and the small amount of air in heavy soils will impede decomposition. Without a coffin, the brain and body will degenerate in ten years; with one, it may take decades.
And that's where the journey of your brain ends. Isn't it a magnificent one? Give your brain a pat on the skull today and wish it well for its future adventures.