X-Message-Number: 26775 Date: Sun, 7 Aug 2005 09:38:56 -0400 From: Thomas Donaldson <> Subject: new neurons and new methods Hello Appraisco! It's very likely true that most neurons remain for a long time. However it's not clear at all from your article that the measurements made by Dr Frisen of brain cell neurons will take account of the formation of new neurons as a minority of neurons. Moreover, our visual cortex is likely to be a brain area which really does take a more permanent form when we're young. Elizabeth Gould did not propose that our neurons underwent a total turnover, either; just that some new neurons occur in all of our cerebral cortex even when we're adults. It's particularly regretable that Frisen did not look at generation of new neurons in our hippocampus, where virtually everyone agrees that this happens. Apparently for monkeys, unlike rats or mice, new neurons migrate from the areas in the supraventricular surface (a skinlike surface surrounding a connected area in our brain filled with ventricular fluid) to many different areas in our brain. In rats and mice they almost entirely migrate to the brain areas dealing with smell. It's also very unlikely that we get a new neuron(s) for every new memory. At that level we'd probably see growth of new synapses connecting different neurons, rather than whole new neurons. Still, even new neurons will eventually be needed if memories to be stored increase as we continue to live. It would be nice if you had given a full, explicit reference in your message. I will do my best to find the original scientific article by Frisen et al in CELL. As for new neurons, it's by now quite clear that we form new neurons. The technique used by Frisen suggests that we'll be soon able to find out just where new neurons go and how many there may be. Best wishes and long long life to all, Thomas Donaldson Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=26775