X-Message-Number: 5029 From: (Thomas Donaldson) Subject: Re: CryoNet #5016 - #5017 Date: Fri, 20 Oct 1995 23:55:20 -0700 (PDT) Greetings: I would agree that Mike can be VERY pessimistic. Moreover, I did specifically point out that Mike is weak on math and might easily have misinterpreted something as turbulence when it was not. HOWEVER ***IN THIS PARTICULAR CASE*** I will hold my ground. Bob, are you seriously claiming to compare Mike to those who believe in ESP? It's important that we all listen to one another, expecially when apparently negative results occur. I was not arguing for Mike's INTERPRETATION of what he saw, but for his STATEMENT of what he saw. And I think it would be very foolish of us to simply shrug that off. That given, I will make some further comments. First, if you reread the Hossman and Sato paper, their cat brain had been actually removed from the cat and turned into an experimental preparation. The cats did not live for much longer after the experiment. That does NOT affect the validity and importance of their results, however. Second, in terms of Mike's interpretationsI would (and should have at the time) point out something important ... and you will see this theme in the next PERIASTRON (which is coming VERY late due to the fact that my computer went down and had to be fixed ... but it is still coming). First, almost all of the brain deterioration that happens after ischemia and other such damaging events does not happen at once. There is a lapse of time. Neuroscientists, for instance, have observed that seizure activity happening AFTER blood flow is restored, or attempts are made to do so, can be very damaging. For us such facts are very hopeful: they mean that if frozen then there may well turn out to be time to fix these problems. The destruction happens later, not immediately on ischemia. Even if someone's brain will become severely damaged by various events IF we tried to bring them back NOW, it does not follow that such damage will be permanently irreparable. Moreover, even our brains need not be completely intact for our memory to survive. (I elaborate on this in the next PERIASTRON). Our hippocampus, by all current evidence, acts as a staging area for memory. Without it, we can't form new declarative memories BUT it plays no role in the actual storage of our memories. This means that our hippocampus could (theoretically) be completely destroyed without compromising our memories for SUSPENSION. It is two very different things to preserve a brain or a person well enough to recover them without injury NOW, and to do that well enough that there is a good prospect that they can be recovered in the future. As I mentioned in my last message, even with destruction of some memory, a revived suspendee would not suffer from any clinical condition doctors have yet seen. His/her problem would not be an inability to learn new memories, nor would this patient show any sign of brain damage at all. The reason why this person could not remember some things would not be because their brain was no longer working: it would be because the memories were no longer there to be recalled. In any case, I was NOT supporting Mike's interpretation of what he saw. But I do think, given who Mike is, that it would be foolish of us not to listen to him. And statements implicitly comparing his OBSERVATIONS to claims to have seen ESP etc etc serve no good scientific purpose. Finally, as for the original observations which touched all this off (possible destruction of dendritic spines) we haven't yet seen the end of that issue. First, it may well be an artifact of the Golgi method. Second, it's not clear what the vanishing of dendritic spines really means for memory... even though formation of dendritic spines IS ONE of the brain events which happens with long term storage. (The others are formation of new dendrites, expansion in area of existing synapses, and formation of entire new synapses). Personally (and this is only a personal opinion, by no means a scientific fact) I am dubious whether or not dendritic spines play an essential role in our memory, though the other factors I mention most certainly do. They are one way in which to increase the effect of the postsynapse present at their end. We may well need them ... just as we need our hippocampus. Best and long long life, Thomas Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=5029