Smarter Brains Run on Sparsely Connected Neurons
sciencedaily.com
sciencedaily.com
https://en.wikipedia.org/wiki/Programmable_Array_Logic#/medi...
If you leave all the connections in place, it's useless.
:)
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.
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?
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.
Wild horses are far smarter than domestic ones, for example.
Your comment fits with my citation of a cavity-IQ correlation, here.
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.)
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.
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 cavitiesI'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.
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.
E.g. - homo-sapiens are considered smarter than homo-erectus and neanderthals despite having smaller brains .. evolution of the hypothalamus, etc.
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.
I mean what is science if not deduction based on observation?