Smarter Brains Run on Sparsely Connected Neurons

https://www.sciencedaily.com/releases/2018/05/180517102236.htm

by ardent_uno • 8 years ago

34 19 8 years ago

yosito• 8 years ago

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?

ridgeguy• 8 years ago

Not an expert (but a background in neurophysiology).

Synaptic pruning (deleting synapses) is an important part of neural development. Here's a ref [1] with a couple of paragraphs (see "Synaptogenesis" and "Synapse Pruning").

Synaptic pruning seems widespread in mammalian neurodevelopment. I wouldn't be surprised to find it's involved in some ultrastructural neural aspects of intelligence.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3722610/

ggggtez2• 8 years ago

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.

Nomentatus5• 8 years ago

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.

ItsMe000001• 8 years ago

Original press release: http://news.rub.de/english/press-releases/2018-05-17-neurosc...

Published article: 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.

kazinator• 8 years ago

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...

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

Nomentatus5• 8 years ago

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

cs702• 8 years ago

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

rando4442• 8 years ago

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.

ggggtez2• 8 years ago

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.

Nomentatus5• 8 years ago

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.)

perl4ever2• 8 years ago

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.

Nomentatus5• 8 years ago

Great article re that:

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...

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.

stevesimmons• 8 years ago

Correlation isn't causation!

WW2 recruits in 1940s would have been teenagers in the 1930s, a time when eating habits and especially consumption of sugary snacks, was very different from today.

Maybe:

  Not poor => Better educated => Higher IQ scores
  Not poor => Family can afford sugary snacks => More cavities

Nomentatus5• 8 years ago

High correlations with immense statistical significance don't imply any one path of causation, but they do imply causation is involved. That doesn't mean A causes B, it may mean D causes A and B, etc. But mere coincidence isn't plausible when your statistical base number in the millions and the effect is large (as this was.) We agree that correlation and causation aren't the same word or concept - I never said anything different, nor would.

I'm proposing a possible explanation (as you have also done!), not claiming proof; you seem to be confusing a claim of evidence (which may indeed be false or misleading, but remains evidence) with a claim of proof. These are different things, esp in Science post-Popper, although conflating the two is very popular, even by scientists, today! I haven't said other explanations are impossible. That's always so. But you might want to argue for your view by finding other supporting evidence.

For example, pro your view, a much better argument on your side is that there was no possibility in those days of controlling for fetal alcohol syndrome - it hadn't been discovered yet. In fact Vernon's studies of Aboriginal IQs also preceded that discovery and FAS turned out to explain most of the lower IQs effect he measured amongst Native populations.

I've added an unecessary "!" here just 'cause you did.

sunstone• 8 years ago

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

Smarter Brains Run on Sparsely Connected Neurons

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