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Student , Cooper Union for the Advancement of Science and Art


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How does life/death manifest itself in the human brain? Is brain death the ultimate end stage of life?

Recently, I watched the TED talk “Stroke of Insight” by Jill Bolte Taylor (http://www.ted.com/talks/jill_bolte_taylor_s_powerful_stroke_of_insight.html), in which she discusses the experience of having a stroke from a scientific perspective. She was able to diagnose herself throughout the process, even as her brain functions slowed or stopped altogether. Her story gives rise to a very important question: what is the connection between life, death, and the human brain?

In my Bioelectricity class this week, we discussed the use of EEG’s to record brain waves. A patient whose EEG reading shows a lack of brain activity is declared to be “brain dead.” In the medical community, “brain death” is considered to be equivalent to “death.” However, many consider this definition of death to be problematic. Even when a patient exhibits a lack of brain activity, her or she may still have functioning organs. The circulatory and respiratory systems, for instance, have been observed to be active in people who are brain dead. Is it really appropriate to define death as the cessation of brain function? Or, should the medical definition of death be modified from its current form?


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    Mar 8 2012: There is something to the fact that, to maintain a living state, the brain requires a pattern of oscillatory activity with the power distributed in certain frequency bands according to the type of activity that the brain is engaging in. (See Rhythms of the Brain by G. Buzsáki.) However, even after a massive epileptic seizure, which typically indicates a widespread state of electrical noise, the brain is usually able to recover these baseline rhythms.

    In PVS, the brain has very little normal electrical activity, but still, the activity is non-zero -- and the brain appears able to wake itself in some cases. There are stories of people waking up from PVS after several years. It's also curious that you can keep a person's body alive for a long time after their brain is declared "dead" as long as you keep blood flowing and oxygen and nutrients at the right levels. Personally I think that implies the organism couldn't really be declared dead to start with. I don't think it's possible to accurately declare an organism dead until rigor mortis sets in and its microbiome begins to consume it -- in my opinion, decay and the succumbing to entropy is the only true sign of death -- and these forces are set in motion very quickly once an organism "actually dies".

    Note that recent research has shown that administering an intravenous dose of Ritalin to a comatose mouse can cause the mouse to wake up almost instantly. They have yet to start human trials, but this may hold real hope for "rebooting the brain". http://web.mit.edu/newsoffice/2011/ritalin-reverse-anesthesia-0922.html

    How long should we keep a PVS patient alive for though? Is it worth 20 years of stress on the family and untold cost of life support? I don't know, but I would say that we need a better understanding of the types of baseline electrical situations from which the brain is able to reboot before we can authoritatively say we know that a patient is actually "brain dead", i.e. beyond the chance of recovery.
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      Mar 8 2012: I agree with Luke somewhat. We have cases where we can flash freeze organisms like nematodes and small fish. At that point they are completely brain dead; no activity is possible with frozen neurons. But we can resuscitate them, warm them up, and they well continue living. The only real way we can declare an organism dead is if the brain is exceptionally degraded or gone from the rest of the organism.
    • Mar 8 2012: Luke, I agree that a lot more research is needed into the relationship between brain activity and the possibility of rescuing a brain-dead patient. An issue that I find especially problematic is organ donation. Once a patient who has consented to organ donation is declared brain dead, his or her organs can legally be harvested. But, what if something could have been done to save the brain dead patient? At the same time, though, I realize that organ donation is an extremely valuable medical tool. Organ harvesting cannot be discontinued as it saves countless lives every single day.
    • Mar 8 2012: In an ideal situation, we would be able to cryo freeze PVS patients for later revival. As a matter of efficacy in typically overburdened hospital systems, letting PVS patients live without life support (spelling their inevitable end) is the most humane course of action for all stakeholders.

      But people like to hold out hope for miraculous revivals. I suppose that's their perogative... but it shouldn't be unduly influenced by a culture that too readily transmits a hope that is far out of line with the reality of the situation (that is, that vast majority of PVS patients never do recover; simply cannot recover).
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        Mar 8 2012: George: actually, waking up a patient from cryo is at least as hard as waking them up from PVS -- you have to deal with not just rebooting the electrical activity in the brain, but rebooting everything else too. It's likely we would need some extra genes spliced into our genomes before this would even work -- I suspect, for example, that during thawing, most of our intracellular RNA would be degraded. Honestly, I don't think freezing a human now and waiting for some future day when we have the tech to properly thaw them out is actually a smart thing to do -- they have to be frozen in the right way in the first place.
        • Mar 8 2012: Thanks for the information Luke.

          I was more thinking from the angle - if we're going to give people hope disproportionate to the effectiveness of the course of action... then we may as well do so in a way that reduces the resource and opportunity cost (not that cryo-freezing/storage for an indefinite period of time is cheap by any means).

          Plus... while I appreciate that it'd be harder to revive a cryogenically frozen person than a PVS patient with comparable technology... the point is that the former is expecting the use of far advanced technology to aid revivification (if possible).

          I mean... have we been able to solidly conclude that the damage caused to a cryo-frozen patient is extreme enough to create information entropy such that any possible future recovery technique is not feasible?

          i.e. If we eventually have the technology to digitize and stitch together the molecular structure of the person, reform them as new, or just operate them virtually... that despite this technology, the damage is so extensive that there isn't enough information (or that it's been too badly disorganized) to even do something like that?
      • Mar 8 2012: To add to what Luke said, I recently read an article ("The economic problems with cryogenically freezing your body," http://io9.com/5889638/the-economic-problems-with-cryogenically-freezing-your-body) that also paints a not-so-desirable picture of cryo. According to this article, there is a high chance that the frozen human will not survive to the day when he or she may be revived. There are quite a few things that can go wrong. If the preservation company decides that not enough money has been set aside for cryo by the client, the client may be thawed prematurely, thus losing any chance of being revived in the future. Also, accidental thawing may occur at any point during the preservation process (during transportation from one facility to another, for instance).
        • Mar 8 2012: I wouldn't engage in cryo-freezing as anything but a last resort measure.

          But if it's a toss-up between occupying hospital/medical space needed by other patients that have a greater chance of recovery and been frozen in order to retain hope... I think the latter is the better option.

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