“Brain size alone can’t explain human cognition”
October 30, 2024 7:12 AM   Subscribe

What's so special about the human brain? A popular science article from Nature with fancy statistical graphics about the distinguishing features of the human brain.
posted by Alex404 (11 comments total) 23 users marked this as a favorite
 
the thing i find is most interesting about the 'higher cognitive functions' associated with humans' enlarged prefrontal cortex is that they're mostly a lazy hack of evolutionarily ancient motor control processes.

PFC loops through basal ganglia, a cluster of nuclei whose pattern of connectivity is mostly preserved over hundreds of millions of years across vertebrate species. BG is associated with motor control - parkinson's disease and huntington's disease affect distinct nodes in the BG network, with increased motor dysfunction as the diseases progress.

if you're a lamprey, which hasn't changed much in half a billion years, motor control is all you need to live your best life. They don't have much of a 'prefrontal cortex' to speak of. It's basically motor cortex sending signals to BG which then gates motor output. simple.

PFC is enlarged in higher primates - and some of the more cunning monkeys - but the connectivity through BG follows the same pattern as motor cortex. the big difference is that instead of directly gating motor output, the cortico-ganglia loops in PFC are gating the delivery of signals from motor cortex to BG, which then gates motor output. in humans, you have 3-4 iterations of this in PFC - a premotor area that gates primary motor cortex, caudal PFC which gates premotor, and rostral PFC gating caudal PFC. at each level the information that's being gated gets more complex, but the algorithm is essentially the same.

there's some additional detail and caveats about how it all plays out, but the basic idea is that you can bootstrap some fairly sophisticated cognitive behaviors using this kind of hierarchical organization - humans aren't really doing anything different than monkeys, they're just doing more of the same thing.

this also explains the protracted neural development observed in humans - in order to train up one hierarchical layer in this scheme, the preceding layer needs to be generating reliable data. You can't learn extremely abstract associations until the concrete stimulus-response circuits are established. if there were some mutation that enlarged human PFC even more than it is now, it's possible the behavioral effects wouldn't even be noticeable until essentially middle age, i.e., there's not evolutionary point to it.
posted by logicpunk at 8:05 AM on October 30 [21 favorites]


(Grandmother hypothesis tho?)
posted by clew at 11:05 AM on October 30 [1 favorite]


They seem to make a mistake in the EQ graph, expanding in two dimensions to represent an increase that is one dimensional making the area look much larger than the quotient.
posted by dances_with_sneetches at 11:36 AM on October 30


ダイヤモンドの城より
ひとの心はミステリー

Daiyamondo-no-shiro-yori
hito-no-kokoro-wa MISUTERI–


More than a castle made of diamond,
a person's heart is a mystery

yt
posted by torokunai at 1:10 PM on October 30


Super interesting. The graphics that compare brain/neuronal development across species relative to life span are remarkable.
posted by bluesky43 at 4:51 PM on October 30


This was fascinating to see and read. I feel like we're still on the very beginning foothills of understanding how brains, particularly human brains, do the things they do. If we allow ourselves to survive long enough, we may actually figure it out.
posted by Mental Wimp at 5:26 PM on October 30 [1 favorite]


“I used to think that the human brain was the most fascinating part of the body. Then I realized, look what’s telling me that.”—Emo Philips.
posted by Horace Rumpole at 7:08 PM on October 30 [2 favorites]


Fuckin’ mice. Idiots
posted by Dokterrock at 11:11 PM on October 30


What if, just hear me out, there’s just an absolute ton of animals out there who have higher functioning brains just like ours, but they just act like they don’t because they see how messy we are, and they just *know* that if we figured out they could understand us, we’d just never leave them alone.

The vole has no desire to listen to us describing the weird dream we had last night when our old shop teacher came to Thanksgiving. The badger doesn’t want to listen to us when we’re drunk and debating about whether or not we should text our ex. The humpback whale, specifically, is tired of our navel gazing.
posted by Ghidorah at 12:41 AM on October 31 [2 favorites]


What if, just hear me out, there’s just an absolute ton of animals out there who have higher functioning brains just like ours, but they just act like they don’t because they see how messy we are, and they just *know* that if we figured out they could understand us, we’d just never leave them alone.

There's not one dang vole that doesn't relish gossip? Yeah, right. Maybe most of them are curmudgeonly and self-species interested, but not one?

That's the equivalent to the theory that some advanced alien species is going to elevate bald men with no fashion sense to top explorer status.
posted by The_Vegetables at 9:35 AM on October 31


it sure looks pretty but man! never did i have to do so much scrolling simply to read an article — and reader view only gets half of it. web designers : give an old man with arthritic hands a break!
posted by toycamera at 1:34 AM on November 1


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