Ask HN: Do newborns have a standardized brain structure? | Hacker News Reader

Ask HN: Do newborns have a standardized brain structure?

11 pointsspeedylight19 comments

To be more exact I was just wondering that when a child is born does their brain have distinct differences in its neural network structures when compared to other newborns—assuming they grow up to be neurotypical people, so not accounting for any genetic predisposition to developing mental illness.

What I really want to know though is when the brain starts responding to its environment and begins evolving as a result of the input it receives from various senses, does it do so from basis that’s shared with all other newborns or is every person truly unique at birth.

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The infant brain has been developing based on feedback from the body for months in-utero. They brain is getting sensory inputs from the fetus's movement as well as external sounds, so it's definitely not a pure function of its genes.

Maternal stress, which the fetus can sense through hormones that cross the placental barrier, is also known to affect development before birth.

From 2 days ago

"Taste of kale makes unborn babies grimace, finds research"

https://www.theguardian.com/science/2022/sep/22/taste-of-kal...

Every person differs in many ways from every other person. Newborns don’t share “standardized” facial features, fingerprints, circulatory systems, etc. Brains certainly differ greatly across individuals.

Babies respond to “inputs” in the womb. The environmental factors that affect brain development (not “evolution”) include maternal hormones, nutrition, drugs and alcohol, even sounds.

Thank you for pointing out environmental factors, it completely crossed my mind while I was writing this

Depends on what level of granularity you're asking about. Does every (neurotypical) newborn have a brain with left and right hemispheres? Yes, of course. Does every (neurotypical) newborn have exactly identical neural wiring right down to the last synapse? Almost certainly not.

The extent to which the wiring is identical, and how much of our intelligence and ability to learn comes "hard wired" is one of the Big Open Questions in neuroscience / cognitive science.

I agree. More details in case they are enlighten: Some areas are localized in the same part of the brain of every person [1] https://en.wikipedia.org/wiki/Human_brain#Structure Some areas are very specialized and in the same spot in "everyone", one of the famous one is the Broca's area that is related to speech https://en.wikipedia.org/wiki/Broca%27s_area

[1] I think there are a few exceptions. <IIRC> If some area is broken sometimes another part may replace the functionality with a lower accuracy. And for example if you are blind, then the visual area may help to interpret the Braille code in your fingerprints. </IIRC>

soapbox The area/function mapping is -far- from nearly universal. Not only can the areas be flipped left/right but they are almost guaranteed to be several cm in some other direction. The maps as we know them are just the ven diagram overlaps for dozens (rarely hundreds) of subjects.

This is one of the great unknowns that keeps me up at night pondering about how it all works.

It's one of those topics that becomes more mindblowing the more you know about it, or related topics such as AI/ML research.

Random examples:

How does sexual attraction get encoded in the brain? Think about how complex and subtle the selection criteria has to be to reliably[1] pick out "same species", but not "same sex of the same species". The distinguishing attributes are subtle, such as slight changes of the fat distribution of the face, and a couple of body ratios[2]. But to identify body ratios, you need to be able to identify bodies, ratios, and have that entire mapping from the visual cortex all the way through to the arousal centre of your brain be learned in a way that is consistent with something encoded in your genetics that was laid down in your neurons before birth, at a time when you had not yet seen anything, let alone male or female humans!

The other one that blows my mind is how terrestrial animals are afraid of heights. This has been studied at length, and despite this the exact mechanism is not perfectly understood. Even babies are afraid of crawling over a ledge. But think about it: what is a ledge? It's not just "an edge", it has to have a certain spatial orientation to be dangerous and scary! This instinct is baked into every brain, but its trigger is a complex combination of head angle, gaze angle, depth perception, and 3D geometry! Even animals that don't have stereoscopic vision are able to identify a dropoff and be afraid of it.

To me the most amazing is how all quadruped grazing animals are able to walk or even run from birth. That's a staggering level of neural training pre-baked before birth! Vision, proprioception, muscle control, everything pre-trained to the point of some animals able to outrun a cheetah on rough terrain mere days after plopping out of their mother! Go ask Boston Dynamics how hard a problem this is to solve...

[1] Actually, the failure modes are educational! Bestiality and furry tendencies indicate that this neural encoding is based on a shared set of traits with all mammals, but with species-specific aspects. Clearly the filters are good, but not perfect.

[2] Apparently just some specific curves suffice: https://www.etsy.com/au/listing/673314609/sexy-lovers-art-pr...

>Do newborns have a standardized brain structure?

No.

Genetic diversity due to isolation of cultures in their environments over the eons has made this impossible.

Still - do twins have the same/similar brain structure?

I would think those are the newborns who start out as close as you can get.

Indeed - and yet I'd think it's not close at all. I bet there is going to be the same level of variation as compared to relative differences between unrelated humans.

I would say it depends on what you call close.

The differences between unrelated newborns would be both genetic & environmental, compared to the identical genetics and nearly identical environments of the twins.

From which point all would begin to diverge further.

Nature vs nurture, an age old topic of conjecture.

The obvious (and prevailing) perspective is both.

Intellectual and psychological traits have some genetic predisposition, yet we should never discount the general adaptability of all minds.

Want science proofs? Consider how twins who grow up apart are strikingly similar, and consider how these examples might diverge from your own (random) characteristics.

It’s funny you mention twins because while I was writing this post I also wanted to pose the question that if a pair of identical twins were raised the exact same way (exact enough that it’s more of a far fetched hypothetical than any sort of realistic scenario) would they then be the exact same person given that they shared not only the same life experiences and therefore memories, but also the stimuli they shared while in the womb from factors like changes in hormone levels, stress, nutrition, smoking/alcohol/drugs use, etc which all affect development as pointed out by the other comments.

It’s an interesting question to think about but I think any answer is going to have a considerable degree of speculation since we don’t fully understand how the brain works and why it’s the way it is.

Exact doesn’t exist. What is meaningful is that twins raised far apart by random parents have striking similarities.

Googling “twins raised apart” provides a handful of stories.

One of the more interesting is the story of the Korean twins having a “huge IQ difference”, the lower experienced less stability in her upbringing. Otherwise their personalities were the same. This is interesting as twins raised together often have different personalities, probably drawn from their (possibly subconscious) intentions not to be too similar.

Agree with everything you say. That said, just to add some context, and for anybody who might not be aware... even "identical" twins aren't actually strictly identical. That probably goes without saying for the most part, but the amount of differences that can be found in monozygotic (identical) twins turns out be somewhat surprising. See:

https://www.mcgill.ca/oss/article/general-science/identical-...

Unique. It shows in learning, memorizing, skills, toy preferences... The wiring of the default neuron network and inner workings are (at leas partly) inherited.

> ... when the brain starts responding to its environment and begins evolving as a result of the input it receives from various senses

In the womb.

Why do you ask?

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