X-Message-Number: 10421 Date: Sun, 13 Sep 1998 08:57:49 -0400 From: Thomas Donaldson <> Subject: CryoNet #10415 - #10418 Hi everyone! I want to thank Jeff Davis very much for his references. It's not clear that our memory STORAGE uses these methods, but I've taken his references and will get and read them. The major point about "scrambled salamander brains" is important and simple. Current ideas about how our memory works suggest that it is encoded in the connections between neurons, quite possibly by the growth or splitting of synapses. This is a fine idea, and probably contains a kernel of truth. However neurons also turn out to be very active, and in those few cases in which identified neurons could be followed for several weeks in living animals, the experimenters found that even the synaptic connections changed constantly. I will have to leave the matter at this level, for no other reason than that its relation to long term memory is now quite unknown. Such observations suggest but certainly do not prove that there is more to long term memory (I mean memory that lasts for years) than simply the nerve cell connections. And that for our own purposes it would be very important indeed to find out just what that "more" may be. Within an individual neuron there might be, for instance, some chemical which increases the general level of connectivity of it with another (this may be an activity which works between them, not one that happens in both in some isolated way). When our brain forms in embryo, different neurons actually grow towards their targets. These targets apparently are not at first defined precisely, but the neurons aim to connect with others of some particular type and location. It may prove useful to learn much more about such growth, with the idea that it just might give clues to how connectivity might persist while the synapses which implement it at any given time change constantly. It's a major problem with this idea that following individual neurons in living animals is not at all easy. It could even be that the observations that found this constant change did not generalize to other brain areas at all. There is more to this, still, when we consider cryonics. If the actual connectivities (I mean the actual synapses and their location) are not primary here, then that could mean that even if we revived a brain, and restored its connectivity, we could discover that it changed and disappeared after only a short time. Why? Because whatever influences maintained it prior to suspension were not restored, only the connectivity was restored. If I were to try to follow connectivity changes in the cerebral cortex, say of a monkey, for several weeks, I would devise an experimental preparation such that the apparatus for looking at a restricted area of the monkey's cortex was surgically implanted early in its life and organized so that it would not come off. Ideally this might even be done before its brain connectivity had developed fully. The idea would be to make a "window" through which we could watch the changes. Making such a window, especially one that would not be outgrown, doesn't sound easy, but still perhaps could be done. The experiments which followed changes in neural connectivity did not look directly at the cerebral cortex. One possibility might be to use a slow-growing animal (say one of the apes) and periodically replace the window apparatus with a larger one. It's helpful here that our brain doesn't grow as much as our body, though it does grow. This would probably work, but take lots of failed tries before it was successful. But it would tell us something important. One major complaint about the use of salamanders is that such animals have far more abilities to recover from brain damage (actually regrowing connections) than mammals. However the current sense on this issue is that our ability at brain repair still exists, though it is frustrated by various other influences in our brains. By removing these frustrating factors we might restore an ability at brain self-repair. And repair and maintenance come awfully close to one another. In any case, thanks again for the references. Best and long long life, Thomas Donaldson Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=10421