X-Message-Number: 13315 From: Thomas Donaldson <> Subject: more about what we know and don't know Date: Sun, 27 Feb 100 22:58:35 +1100 (EST) Hi everyone, once more: While I actually sympathize with Ettinger's comments about how often experts have turned out to be quite wrong, I myself would say that the strongest argument for keeping those now in suspension rather than giving up on them comes from our lack of understanding of how brains work. Yes, compared to the situation 15 years ago we know a lot more. But we still don't know everything we'd want. Yes, the formation of memory has been traced up to the formation of new synapses between neurons (the authors of the paper that did this state that they can prove that these synapses connect dendrites and axons which already have connections, but their methods do not tell whether or not NEW connections between dendrites and axons which were not connected before might also arise. (Such connections, depending strongly on just how our brains work, would be most needed when we learn or think something new). Furthermore, given that synapses seem to change spontaneously with time, this pushes the problem of memory onto another stage, but does not completely solve it. Yes, it tells us to look at the interconnections between neurons on a fine scale to work out just what someone may hold in their memory. But how then do we retain memories which stretch back into our childhood? I am actually confident that we will get answers to that problem in the relatively near future: much money and effort is going into the study of the details of how memory works, in both animals and humans (and by all that we now know, the processes are quite close). A second issue also needs tying in with memory. It has turned out that in at least one primate, the formation of new neurons occurs not just between the dentate gyrus and the rest of the hippocampus (a place where the formation of new neurons has been noticed for several years now, in several different animals) but in other brain regions, too. No one can now say just what roles these new neurons may take, but it's also hard to ignore the fact that virtually all primates (except the most primitive ones) tend to be brighter than most other animals. Perhaps those new neurons create the connections for totally new memories? No one knows. For comparison, it seems that the olfactory regions in rats' brains also form new neurons. Hmmm. Best and long long life for all, Thomas Donaldson Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=13315