X-Message-Number: 3038 Newsgroups: sci.cryonics Subject: Re: An irreverent introduction to Cryonics Message-ID: <> From: (Joe Strout) Date: 28 Aug 94 11:55:49 -0500 References: <> In article <>, (Brent Fox) writes: > Have you seen an estimation of what the total information storage > capacity of the human brain is? In Carl Sagan's _Cosmos_, he stated > that the brain has on the order of 10^14 neural connections in the cerebral > cortex. Assuming each connection would be equivalent to 1 bit, > taking this further would yield a capacity of 12.382Tb. > ... (calculations omitted, but thanks for including) > I would be interested in hearing your thoughts on this. Your arithmetic looks good, but I'd say that 1 bit/connection is a gross underestimate. Consider that there are many different types of connections, which differ in their natural (unstimulated) firing rate, effect on the postsynaptic (next) cell, in their directed or diffuse effects, etc. If there are, say, 256 functional classes of synapses, then that's 8 bits already. Then there's connection strength -- i.e., how much influence the connection has on the postsynaptic neuron. That's an analog value, so the question would be: into how many discrete steps do you want to break the continually varying values? It's the same question that the music industry faced when inventing CD players: sound pressure is a continuous variable, approximated by 32-bit values (if I remember correctly). So we're up to 40 bits or so. Then comes the real problem: it is extremely relevant what these connections connect. It's not a uniform pattern; it's circuitry, and so you have to take into account some way of specifying where the synapse "comes from" and "goes to". That is likely to increase your bits per connection by an order of magnitude or two. Of course, this is mostly loosey-goosey speculation at this point, but I hope to be doing research soon to help determine exactly how much information needs to be stored to represent the functional properties of real neural networks. Keep an eye on the neurosci groups for more details as they arise. -- |o| ///// Joe Strout |o| |o| | @ @ Neuroscience |o| |o| C _) U. C. San Diego |o| |o| \ o La Jolla, CA |o| Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=3038