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

John Clark johnkclark at gmail.com
Sun Jan 19 12:42:34 UTC 2020

On Sat, Jan 18, 2020 at 9:31 PM Stuart LaForge via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

> 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.
> * > Landauer's law is responsible in that it is defined as the lowest
> possible energy it would take to erase a bit in a 100% efficient  computer.
> *

Yes Landauer's law will tell you the least amount of energy needed to erase
one bit of information, but if you want to use more energy than that it's
OK with Landauer, and the human brain uses trillions of times more energy
than that lower limit.

*> It is like a thermodynamic limit*

It gives a lower limit but not a upper one, you are free to use as much
energy as you want to erase one bit of information. And the brain uses a
LOT more.

> *> and it costs  biological brains more to erase bits because they are
> kludgy  naturally-evolved processors that uses selective movement of ions
> across membranes*

Yes, and that kludgy nature is the very reason Landauer's law doesn't play
an important role in the brain. Nothing in biology is anywhere near to
running up against Landauer's limit, it's far far too small, Biologists can
safely ignore it.

> *> rather than a simple current of electrons to perform calculations.*

That's much less kludgy but even todays microprocessor designers can safely
ignore Landauer's law and can continue to do so for another decade or two
because factors that have nothing to do with Landauer produce much more
heat. When they've conquered those factors then they can worry about

*> Seems like it should be a testable hypothesis.*

It is. You gave the formula for the minimum amount of energy needed to
erase one bit of information in your last post, just plug in the numbers
for body temperature and the formula will give you a ridiculously small
number, a number that remains ridiculously small even if you multiply it by
86 billion (the number of neurons in the human brain) and then multiply it
again by 15,000 (the maximum number of dendrites any neuron has been
observed to have). Biologists would do well to spend their time studying
things other than Landauer, it just isn't important for there subject.

John K Clark
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