X-Message-Number: 22259 Date: Sun, 27 Jul 2003 10:03:32 -0400 From: Thomas Donaldson <> Subject: CryoNet #21722 - #21727 For Francois, thought I should apologize for the lateness of this reply: You had a scenario for turning a human being into a computer. It fails not just for possible philosophical reasons, but because it seems to have an underlying assumption that at least our neurons work like computers. First, signals are sent through structures (and lines) called axons, and received through other distinct structures called dendrites. The connection between them is a synapse. Second, memory in our brain (I refer to true long term memory, not the changes at a synapse which occur at an early stage of learning and allow the longer stages to come into force) involves the growth of new connections between neurons. Even as single bits it does not exist in any single neuron, but in its connections to many others. Third, at least 2 brain areas and some scientists think ALL brain areas produce NEW neurons, which form new connections and all the rest. The dentate gyrus, in our hippocampus, lies deep inside our brain; the other unquestioned area which makes new neurons is the lining of our ventricles (areas within our brain which are filled with a fluid very like spinal fluid). Fourth, neural signals are not single bits. It turns out that the most efficient way of sending signals between neurons consists of repeated blips at a fixed rate. This is the most efficient because (remember?) many neurons have thousands of connections and many of them may all be working at once; some way to distinguish one message from another is needed. Given that the number of neurons to which one neuron might someday connect is very large, it won't work to have wires between all of them at once, and rather than grow connections activate already existing ones. Your nanomachine which introduces new neurons would also have to be constantly active to deal with growth of new neurons... and their multiple future connections. In terms of imitating brain activity, that nanomachine would need to be built as a PART of the brain rather than something that comes in from outside and then goes away, leaving a human with a computer brain. At this point it becomes unclear whether a system which grows new connections and new neurons in response to its own reactions (inner and outer) might not look a lot like the biological system it was designed to replace. Best wishes and long long life to all, Thomas Donaldson Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=22259