
Why Your Brain Seems Mostly Dormant - dnetesn
http://nautil.us/issue/27/dark-matter/heres-why-your-brain-seems-mostly-dormant-rd
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sudo_bang_bang
"The human brain, which accounts for less than 2 percent of the body’s mass,
uses 20 percent of its calorie budget, or three bananas worth of energy a day.
That’s remarkably low, given that spikes require a lot of energy."

What is amazing about this fact is that this is only 20 watts of power. The
brain computes at 10 quadrillion calculations per second. While the largest
supercomputer (China’s Tianhe-2) is at 34 quadrillion and has "beat" the human
brain, it comparatively runs at 24 megawatts of power [1]

[1] [http://waitbutwhy.com/2015/01/artificial-intelligence-
revolu...](http://waitbutwhy.com/2015/01/artificial-intelligence-
revolution-1.html)

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Jun8
Yes! This was the biggest flaw in _The Matrix_ (which I otherwise love): it
had machines using human bodies as power sources whereas they could have used
_human brains_ for computational power leading to huge power efficiency.

Think about somehow hooking up a brain to a computer which can interpret the
neural code. Then you have the best known general purpose AI machine running
on 20W. Now combine hundreds, thousands of them. Not human brains, of course,
but say monkey brains. DARPA already conducted some experiments in this area
([http://www.kurzweilai.net/darpa-links-brain-waves-sensors-
an...](http://www.kurzweilai.net/darpa-links-brain-waves-sensors-and-
algorithms-to-detect-targets))

~~~
krapp
>it had machines using human bodies as power sources whereas they could have
used human brains for computational power leading to huge power efficiency.

That was apparently the original intent, that the Matrix used human brains as
a neural net. But the script was changed to "humans = batteries" because of
fears audiences wouldn't be able to comprehend it[0].

[0][https://scifi.stackexchange.com/questions/19817/was-
executiv...](https://scifi.stackexchange.com/questions/19817/was-executive-
meddling-the-cause-of-humans-as-batteries-in-the-matrix)

~~~
jonnathanson
The brains- _as_ -the-Matrix conceit would have been much more powerful. Damn.
Lots of symbolic value, and a statement on human culture, human nature, and
complacency vs. untapped potential.

I'm going to go ahead and pretend that's what actually happens. :)

~~~
krapp
It is _possible_ that when Morpheus described the 'true purpose' of the
Matrix, he didn't actually know what he was talking about. I think that's the
excuse most people use. It was a best guess based on piecemeal information
(and possibly deliberate misinformation by the machines.)

Not actually canon but it'll do.

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nickledave
What this article leaves out is that sparse coding is most common in neocortex
(the wrinkly outside part of your brain). In structures underneath there are a
lot of brain cells that fire away all the time: the thalamus, the basal
ganglia, the dopamine cells in the midbrain that fire like pacemakers. I've
recorded from the cerebellum in deeply anesthetized animals; there is still a
lot of spiking going on in there. Presumably the same thing is true for
humans. So sparse coding is nifty--and people have made some cool algorithms
with it, cf. Cris Rozell's work--but it doesn't mean you're not using your
whole brain

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snake117
> Today we know that a large population of _cortical_ neurons are “silent.”

> This energy budget puts limits on how much of the _cortex_ can be engaged at
> once

I passed over it during my first read through as well. But at certain parts
the author did state explicitly that these were cortical neurons.

~~~
nickledave
She totally does say they're cortical neurons. But it seems the point of the
article is that most of the brain is dormant. I'm not sure that most of the
brain is dormant.

~~~
jonknee
Except that's not how it reads:

> The quiet neurons might be doing more than refining perceptions. Though they
> spike infrequently, we know from intracellular recordings that they still
> receive inputs from other neurons, which causes their membrane voltages to
> fluctuate. The sum of these fluctuations and spikes constitute what’s
> commonly known as brain waves. Over the past 15 years scientists have begun
> to amass evidence that these brain waves play an active role in information
> processing, shunting some neural inputs while enhancing others, for example,
> or altering the timing of spikes. This suggests that spikes are not the sole
> information-carrying signal in the brain, and that, in turn, the “inactive”
> neurons are doing much more than it seems.

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reilly3000
If neurons are polymorphic functions, not keepers of state, it would stand to
reason that certain functions at the root of a dependency tree would get more
use than some obscure branches. Is it overreaching to suggest that object
orientation has been detrimental to our understanding of cognitive processes?

I can think of so many memories of images of brains drawn into regions.
Usually for comedic effect. But the symbol is powerful. Different 'parts' of
the brain know or do things related to a specific domain. To imagine the brain
does crazy things like biological macros is harder to draw in 2D, but likely
much more accurate to the real world than having a portion of my brain
dedicated to XYZ...

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jmsdnns
According to this article, the brain has implemented epoll(4). Wake up the
neuron when you want to use it. The upper bound is tied to how many active
firings are happening concurrently.

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webnrrd2k
This is just speculation, but I'd think it would be important for the brain to
have a way to manage it's memories... you wouldn't want memories just randomly
appearing, all the time There has to be some way to orchestrate memories, and
I wouldn't be surprised if the more active neurons are involved in that
orchestration. In other words, couldn't those exceedingly active neurons be
contributing to _suppressing_ memories?

~~~
nickledave
It would be interesting if active neurons were suppressing memories but I
don't know of any evidence in support of that idea.

Most of the articles cited by the author don't deal with neurons that are
directly involved in memory. The articles described the activity of neurons in
primary sensory areas: the neurons in cortex that receive direct input from
the periphery, or at least are the closest to neurons in the periphery in
terms of number of connections between them. One exception is the article she
cites about the hippocampus, but this area is required only for _forming_
memories--once the memories have formed, they live somewhere else, but
probably not in the primary sensory areas. Okay, maybe memories are a
distributed network that includes neurons in primary sensory areas...but it
would be weird to also have the main sensory area also be the place where
memories live.

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noselfrighteous
It might make a lot of sense actually. It could serve to speed up instinctive
responses to stimuli which have been encountered before, i.e. whipping your
finger away from a hot surface.

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unepipe
I think I understand what you're getting at, but the example you gave is not a
learned act, it's a reflex action. It bypasses your brain entirely, you
generally recognize the pain after you reflexively withdraw your hand.

source:
[https://en.wikipedia.org/wiki/Withdrawal_reflex](https://en.wikipedia.org/wiki/Withdrawal_reflex)

~~~
etiam
Reflexes can be, and are frequently, modulated by parts of the nervous system
more inclined to learning.

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avz
Software neural networks are a poor approximation of biological ones, but it
may still be interesting to compare spike frequency distribution to see how
general this observation is.

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yodaspi
To those in the know - do these "spikes" vary in voltage or is a spike always
the same like in a computer?

