
Smarter Brains Run on Sparsely Connected Neurons - ardent_uno
https://www.sciencedaily.com/releases/2018/05/180517102236.htm
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kazinator
You've got to burn some fuses so that only the _right_ connections remain, to
have a useful programmable logic array.

[https://en.wikipedia.org/wiki/Programmable_Array_Logic#/medi...](https://en.wikipedia.org/wiki/Programmable_Array_Logic#/media/File:Programmable_Logic_Device.svg)

If you leave all the connections in place, it's useless.

:)

~~~
Nomentatus
True. Yet we do also grow new ones - to set up the next cull, one supposes.

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ItsMe000001
Original press release: [http://news.rub.de/english/press-
releases/2018-05-17-neurosc...](http://news.rub.de/english/press-
releases/2018-05-17-neuroscience-smarter-brains-run-sparsely-connected-
neurons)

Published article:
[https://www.nature.com/articles/s41467-018-04268-8](https://www.nature.com/articles/s41467-018-04268-8)

Abstract:

> _Previous research has demonstrated that individuals with higher
> intelligence are more likely to have larger gray matter volume in brain
> areas predominantly located in parieto-frontal regions. These findings were
> usually interpreted to mean that individuals with more cortical brain volume
> possess more neurons and thus exhibit more computational capacity during
> reasoning. In addition, neuroimaging studies have shown that intelligent
> individuals, despite their larger brains, tend to exhibit lower rates of
> brain activity during reasoning. However, the microstructural architecture
> underlying both observations remains unclear. By combining advanced multi-
> shell diffusion tensor imaging with a culture-fair matrix-reasoning test, we
> found that higher intelligence in healthy individuals is related to lower
> values of dendritic density and arborization. These results suggest that the
> neuronal circuitry associated with higher intelligence is organized in a
> sparse and efficient manner, fostering more directed information processing
> and less cortical activity during reasoning._

For data availability see "Data availability" in the Nature article.

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yosito
You must unlearn what you have learned.

This is a very interesting, counter-intuitive finding. My first reaction was
"Oh! Maybe you can kill some dendrites to make someone smarter". My wishful
thinking side wants to say "This is why there's a correlation between drinking
a lot and being intelligent". I don't really think that's a valid conclusion
to draw from this study, but it was the first thing that popped into my mind.
The main reason, beside common sense, that it's probably not a valid
conclusion is that there's a correlation between intelligence and fewer
dendrites, but that doesn't mean that fewer dendrites causes intelligence. It
could be that intelligent people have fewer dendrites because they don't need
as many as other people.

Can anyone familiar with the science weigh in on what implications this might
have for enhancing people's intelligence?

~~~
ggggtez
My guess is that "smarter" people have trained their brain's neural network to
identify patterns with less "watts". Likely, the total power consumption of a
brain is more or less stable, due to heating/cooling considerations, so less
connections (but more efficient ones) lets them have more compute power.

~~~
Nomentatus
Agreed. I'd say, a big part of what makes smarter people smarter is
encountering more varied problems and environmental conditions that allow more
kinds of pruning in more areas.

Wild horses are far smarter than domestic ones, for example.

Your comment fits with my citation of a cavity-IQ correlation, here.

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Nomentatus
There is a very strong correlation between cavities and IQ, as well -
suggesting that high-IQ peeps are "gas-guzzlers" who prioritize getting more
energy in. Having a network that burns less (because fewer connections) might
be the other half of that equation.

The source is Vernon's old book from decades back, he dismissed a lot of
science using this factoid as a counterexample; to him, this was a proof that
looking for correlations was pointless. I find it more significant. Someone
who didn't want to go to the front in WWII occupied himself by going through
all American recruits' data and looking for correlations in order to look too
busy to be reassigned to combat. The largest correlation they found, as I
remember, with tested IQ was number of cavities (more, better.)

~~~
perl4ever
Maybe there is a particular gut biome that produces both cavities and smarts.
Recently there's been various news stories about how such microbes mediate
Alzheimers, Parkinsons, and maybe other things. And it's been known for a long
time that many psychotropic drugs lead to diabetes and weight gain, so
metabolism and sugar seem like they are related to everything.

~~~
Nomentatus
Great article re that:

[https://www.nature.com/articles/ncomms7342#affil-
auth](https://www.nature.com/articles/ncomms7342#affil-auth)

and choline (see above URL) matters for the brain:

The Case for Choline The nutrient is essential for brain development and much
more, but most Americans get nowhere near enough. By Hara Estroff Marano,
published on January 3, 2017 - last reviewed on March 6, 2017

[https://www.psychologytoday.com/articles/201701/the-case-
cho...](https://www.psychologytoday.com/articles/201701/the-case-
choline?destination=node%2F1099765)

BUT - the modern diet produces more cavities, the ancient diet more choline
(better for brain development.) So more work is needed for this hypothesis
than what I've cited above. The bug that causes cavities from sucrose exposure
(and you're right, there is a specific one) might have an IQ effect too.
Certainly not impossible.

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cs702
As the original article[a] mentions, there is already quite a bit of evidence
in the literature that bigger brains are associated with higher IQ. The key
contribution of this work is that it finds evidence that neuronal circuitry
that is organized in a sparser (i.e., more computationally efficient) manner
is also associated with higher IQ.

In other words, the evidence suggests that intelligence (as measured by IQ) is
a function not only of brain size, but also a function of how _efficiently_
the brain works.

[a]
[https://www.nature.com/articles/s41467-018-04268-8.pdf](https://www.nature.com/articles/s41467-018-04268-8.pdf)

~~~
rando444
While it's nice to have more evidence, isn't this mostly accepted from just
following general anthropology?

E.g. - homo-sapiens are considered smarter than homo-erectus and neanderthals
despite having smaller brains .. evolution of the hypothalamus, etc.

~~~
ggggtez
Sorry that's not how science works. You can't just "look" and "know" the
answer. A mouse has a smaller brain than a human, does that mean the mouse is
smarter? An elephant has a bigger brain, does that mean the elephant is
smarter? No, you need to actually methodically prove something is true, you
can't just guess. We have no living neanderthals or other humanoids to test
our theories against. If you go cross species, there are too many variables to
account for.

~~~
jbattle
There is a rule of thumb that relates the size of the brain to the size of the
body. A bigger needs more brain mass just to operate (more nerve endings?).

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

~~~
perl4ever
I don't think it is intuitively obvious why the brain needs to scale with the
body. An elephant would seem to have roughly the same processing needs as a
mouse. Maybe 25% more for the trunk or something, but not in proportion to its
vastly larger size.

Regarding nerve endings, I think it can be shown that the sense of touch does
not have as high resolution as you might think,* so I'm not sure more surface
area requires more nerves.

*I recall reading somewhere about a simple experiment where someone touches you with one or two pins and you try to determine whether it is one or two. At a certain distance apart you can't tell if you don't look.

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sunstone
Sure, "As simple as possible but not simpler", as once said by a guy with
sparsely connected neurons.

