X-Message-Number: 3863 From: (Joseph J. Strout) Subject: SCI.CRYONICS Re: Uploading Date: Fri, 17 Feb 1995 09:15:30 -0800 (PST) > From: John K Clark <> > Joseph J. Strout Wrote: > >the most basic signals in a neuron spread electrotonically, > >i.e. at the speed of light. > > Electromagnetic interactions occur at the speed of light in > neurons just as they do in all matter, even rocks, but their not > signals unless they convey information. And they do! I should have been more explicit about the signals I was talking about. Synapses (chemical or electric) cause a change in the voltage of the membrane of the postsynaptic cell -- *locally* -- and this voltage change spreads electrotonically over the cell. This is how synaptic inputs are integrated over space (i.e., from their various sites around the neuron), resulting in some combined voltage at the axon hillock, many microns away, which (mostly) determines whether or not an action potential is fired. These electrical signals are crucial to the function of the cell, and act at lightspeed over fairly large (on a cellular scale) distances. Moreover, they are critically dependent on the geometry of the cell (e.g., branch points, dendritic spines, etc.), which is why uploading appears to require determining cellular morphology to very high resolution... Anyway, to speed up the entire system, as you suggest, you will have to either have signals which travel faster than light, reduce the scale of the system proportionately, or come up with some shortcuts which you can compute faster than electrical potentials can integrate. The first is clearly implausible, and the latter two would probably produce only mild increases in speed. 5 or 10 times faster I might believe, but billions? It seems unlikely. Joe Strout Neuroscience, UCSD Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=3863