[ExI] Scientists Discovered ?Mini-Computers? in Human Neurons?and That?s Great News for AI

John Clark johnkclark at gmail.com
Sat Jan 18 22:48:57 UTC 2020

On Sat, Jan 18, 2020 at 3:18 PM Stuart LaForge via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

> * > Yes, the discovery that dendrites have their own calcium-mediated
> action potentials that can form biological XOR logic gates is very  cool
> and amazing.*

I agree, it's a significant discovery.

> * > It also solves a minor mystery in physiology: the human brain is
> typically only about 2% the mass of the body, yet accounts for
> approximately 20% of its energy requirements. So while you are at  rest,
> your brain burns about a fifth of the total calories you are  burning
> despite having only 2% of your cells. If dendrites are XOR or  another
> irreversible logic gate, then dendrites like such gates in  general, erase
> information. This is because you have 2-bits going into  the XOR gate but
> only 1-bit coming out. By Landauer's law,  E>=k*T*ln(2), this must cost
> energy and increase the entropy of your  environment. Since each neuron can
> have something like 5 dendrites and  there are some 10^11 neurons, then
> that's a lot of bits being erased  and a lot of heat and entropy being
> generated, and calories burned,  just by thinking.*

Landauer's law can't be responsible for the high energy usage of the brain,
dendrites are not nearly small enough or fast enough for it to be
important. At body temperature Landauer says you could erase 10^11 bits a
second and use only 2.8* 10^-10 watts of energy.  And remember signals in
the brain only travel at a few hundred meters a second. Even our best
microprocessors are much too large and much too slow for Landauer's law to
be important, although in about 20 years that could change and we'll have
to start thinking about reversible computing.

John K Clark
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