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Comment by RcouF1uZ4gsC | Hacker News Reader

Neurosurgeons have been using hypothermia (cooling down the body) and circulatory arrest (stopping the heart) to treat complicated brain aneurysms since the 1980's. Some of the outcomes have been very good.

http://ether.stanford.edu/library/neuroanesthesia/SNACC%20Re...

When a person is in that state, they have no signs of life - no heartbeat and no blood to the brain, yet a significant portion of the time, they do well.

From the article, it looks like they have done this for up to 50 minutes. " The median duration of complete arrest in our series was 11 minutes; the range was 7 to 53 minutes. This is consistent with reports from other neurological surgeons who have employed extracorporeal circulation for intracranial vascular surgery "

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I wonder how different the experience of waking up from induced hypothermia is from, say, a coma. From my understanding, in a coma there is sometimes brain activity, up to the point that some people end up with Locked-in syndrome(LIS).

An example is Martin Pistorius, who has vivid memories of his time in his pseudocoma. That means his sense of self was intact throughout that experience. That colors what it feels like to "escape" from the coma. In dreams, we usually have a sense of self, i.e. we "come back" to reality.

There are also people who experience the subjective Near-death experience (NDE) which sometimes involves bodily detachment, etc. but presumably this NDE feels like it's occurring to that person's self. When under anaesthesia, waking up from it is more like waking up from a really deep nap, and from my experience, is easy to integrate.

Now, when waking up from induced hypothermia, does the brain slowly kick on different modules? Does the brain snap back to the last thought the person was having? To use a programming analogy, does the brain save state in a physical way? Or is it like restarting a computer fresh?

This is such a cool technique. Thank you for sharing info on it.

"An example is Martin Pistorius, who has vivid memories of his time in his pseudocoma. That means his sense of self was intact throughout that experience."

Or they could just be false memories.

6 years of false memories? (edit: corrected the duration of his LIS)

I remember the movie about LIS.. I couldn't bear to watch it. 6 years of it is beyond insane.

If 6 years had passed with limited sensory input, and you were pretty sure you remembered all of it, how would you know if that's true?

How much detail do we really remember of our own last 6 years of fully awake, conscious existence not spent in such a state?

I feel like once you get to such a length of time you can't trust your own memory of it. Obviously he could know enough to say "I was conscious during some point of that time window" but measuring it would be hard.

The hard problem is when electrical activity stops in the brain, which can continue for a time even without blood flow.

Why is this a problem (or am I dumb)?

Our current understanding seems to be that the electrical activity of the brain is what maintains the mind-consciousness system. (From a physical/materialist pov)

I assume OP wants to know why we can't provide electrical activity manually.

This seems to be one of the ancillary benefits of Neuralink, although I could be wrong, I'm not super familiar with their entire road-map.

So in other words it's like RAM, just the power off and all is lost.

Life must be sustained, once it is lost, it seems that there is a bell that cannot be un-rung.

However, our understanding of how much energy it takes to sustain life at a minimum seems to keep decreasing, like higher efficiency RAM in low-power mode.

Nah, there have been cases with short temporary flat EEG that came back to life, which is why the guidelines specify the duration for declaring someone dead in this way. Those people suffered no memory or identity loss, so electric activity is not related. Connectome structure and tuned bioelectrical responses based on cell cytoplasm gradients, receptor structure and number tuned by a bunch of either RNA or proteins the most likely candidate. So the better analogy is it's like flash memory, left unpowered but running for too long the neurons will change.

Restarting the brain from that flatlined state is therefore possible, we just don't know how to do that properly. Most importantly, it won't do any good if the brain is damaged and is rarely useful.

At that point your brain is “off”. Having a non functioning heart doesn’t seem that noteworthy in this context given that we do straight up heart transplants.

My guess at a computer analogy: Start program -> Delete program -> Crash process -> Resurrection of process impossible.

The program being the bootstrapping mechanism that is present in a baby's brain. The process being consciousness.

Even if the bootstrapping mechanism was still present in the brain, we might not know how to call it and even if we did we would lose everything that was in memory at the time of the crash.

Reverse core dumps are possible, so I'm not sure this analogy is perfectly appropriate.

Analogies aren’t meant to be 100% perfect. They are meant to provide a framework to understand a problem.

I always say: Analogies are like raccoons.

a core dump of the brain is pretty damn big... so that’s not really saying much; just that maybe we don’t have a man data to restore from

It makes you wonder if our brains work as RAM or as a more long-term storage when "rebooted".

IIRC some girl survived extremely long brain arrest after drowning in an ice lake. She cryo-preserved herself unwillingly.

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