2007-09-22

The Slow Road Down 2

Well, that was a bit premature of me. I haven't had time to continue the line of thinking from my previous post.

But I can at least point out the obvious.

As you can see from the graph in the previous post, the final appearance is not so very different from the initial appearance. Even after 48 hours, the neural membranes, while indistinct, still seem to be intact. The nucleus and nucleolus may be damaged, but they are still visible. Nissl bodies (rough endoplasmic reticulum) may be being dismantled. Vacuoles emerge, perhaps the cell's attempt to quarantine emerging debris. The axons, while damaged, are still very identifiable.

The cell is in grave crisis. It would not spontaneously revive even with the resumption of circulaton and respiration after a few minutes, as we know from experience. But perhaps new therapies may be developed which could help either slow the damage to the cell or put it in a better position to repair itself, if for some reason circulation and respiration were to resume.

But if we accept the theory that identity-critical information is stored in synaptic circuitry, then the intracellular crisis is in some sense not key. In theory, if the objective were merely to preserve identity-critical information for the future, it might be adequate that the general external structure of the cell and its synaptic connections be preserved. Synapses may be flexibly "stored" in membranes or cytoskeleton, so that even significant distortions of the cell by generalized edema would not erase the "memory" of the memory, so to speak.

It would be useful to know how long-term memories and personality correlates are stored in the brain; for example, how long-term memories are 'consolidated' physically. If we knew the answer to this question we would be in a much better position to know what we were trying to preserve, and thus, we would be in a much better position to know how to preserve it.

If the 48-hour post-mortem brain in the figure in the previous post were to be preserved, would people in the indefinitely-distant future be able to identify the synaptic circuitry from what remained, copy/transfer this information to another medium, and then restore the patient (in this case, a dog) to life? Or, would people in a probably more distant future be able to use this same information to actually repair the heavily damaged cells, perhaps using nanoscale machines? If the unique, identity-critical information is retrievable, then, in theory, the non-unique structure (healthy, normal neurons) could be restored by however much effort.

2 comments:

V.R.Manoj said...

Hi Greg,
The answer is not as simple as simply repairing the cell using nanoscale machines. You see, when a cell is dead, it just does not stay the way it does. A cell could lyse (die) because of differences in osmotic pressure. This means that the information contained within the cell, genetic and otherwise, would quickly get denatured. So, it may not be entirely possible to restore the cell as depicted in fantastic animations. However, if a living person were to store his genetic information in a cell bank, alongwith a recording of his biorhythms, then it is quite possible to hypothesize that a future generation advanced in technology would be able to revive such a person.

Regards,
V.R.Manoj.
http://cyborgfantasy.blogspot.com

Arcturus Gregory said...

Hi Manoj,

The important thing about knowing when cells lyse is to know how long one has to try to preserve the cells as they are.

I think osmotic pressure indeed is one of the initial reasons neurons lyse in people whose circulation and respiration stop indefinitely. As you say, the spillage is not a good thing and although a forensic scientist of the future might be able to reconstruct where the neuron was by identifying the debris, this is not a good situation.

However, it's not clear that identity-critical information is stored in genes or anything else inside the cell, if the individual "mind" is stored mainly in synaptic connections.

But it would probably be a good idea for other reasons to store genetic material, and it is not too expensive to freeze these small samples. Especially if one is attached to one's physical appearance. But if one is ready to become a cyborg... :)

Greg