5 ms·

The most obvious hypothesis to me is that the (missing) inside parts of the brain is much less important than the (remaining) outer structures

dahart 11y ago
I have a friend working on the Connectome project (http://cbs.fas.harvard.edu/science/connectome-project http://cbs.fas.harvard.edu/science/connectome-project) who told me last summer that all brain logic happens in the outer millimeter of tissue, everything inside is essentially routing. I'm summarizing his summary, so I'm certain it's more complex than that, but to a first order approximation, I'd guess your guess is correct! And so it wouldn't be particularly surprising that someone with cavities in their brain could be smart. One might expect deficiencies of some sort, but one might be speculating; I probably wouldn't bet on it.
- mistaken 11y ago
  This might even be useful for simulating brains, since the hollow brain model seems to be a lot simpler than a fully connected one.
- amelius 11y ago
  Uhm, but why isn't the routing essential for processing? And why is it there in the first place? In other words, why wouldn't evolution eliminate this costly and unnecessary part of the brain?
  - trhway 11y ago
    it was mentioned that the condition develops gradually from the normal brain. So it seems pretty plausible that in some people the brain successfully rewires in parallel with and in response to the development of the condition so that direct white matter connections get functionally replaced by some kind of mesh-style network in the gray matter layer. While this may suggest that typical amount of white matter may be not strictly necessary, the significantly less than 100% success rate of such rewiring may explain why evolution hasn't gone this way .
    - rayedearthstar 11y ago
      This is quite unconvincing: the evolutionary advantage of, let's say, all animals the size of lemurs, having human level intelligence is such that pressure to find this rewiring would have been unprecedented. I think more data and research is needed here. My feeling is that when a few dozen of such cases are closely studied, interesting patterns will emerge. It is surprising that these cases exhibit high IQ and no immediate signs of dysfunction, but it would be absolutely extraordinary if no patterns of difference vs. typical brain were found at all.
      - ZenPsycho 11y ago
        evolutionary trees are littered with branches that have thus far been unable to overcome local maxima- Our eyes' retinas for instance, have optic nerves that connect on the light sensitive surface, blocking a huge portion of valuable photons, instead of the logical place to connect them- on the REAR of the retina- as squid and octopus retinas have been connected in their completely independent eye evolution. Once something works "good enough" there's not really any selective pressure to eliminate obvious design flaws if they don't particularly impede reproduction or survival.
redwood 11y ago
Or that the vital bits relocate to the spinal column
deleted 11y ago
[deleted]
- api 11y ago
  If all that tissue is not needed, then why did evolution conserve it? It consumes energy, adds size, and increases weight and head size which reduces agility. I really dislike "Chief Wiggum skepticism" that likes to just hand wave away and cheaply dismiss amazing things that might teach us a lot.
  - deleted 11y ago
    [deleted]
  - awalton 11y ago
    > If all that tissue is not needed, then why did evolution conserve it? We don't need two kidneys, two lungs, most of our liver, arms, legs, two eyes, ears, etc. These things just make us better at surviving - more likely to make it out of childhood and to an age where we can reproduce. Turns out, we don't quite need all that matter in our heads either, it just makes it more likely we'd survive some traumatic brain injury. If this guy experienced a TBI with this little brain tissue, there's probably no chance of any meaningful recovery left. Meanwhile we see non-diseased brains recover from injuries that look immediately fatal, like having spikes driven completely through skulls. What we've known is that our bodies are remarkably resilient to many kinds of injuries. This just extends what we know of our resiliency to this class of injury. It's also important to realize that hydrocephalus like this is a "small damage over time" type of injury usually - this patient didn't go to sleep with most of his brain matter intact and wake up with it gone, it was gradually lost over months or even years during his childhood as csf slowly increased in volume, obliterating cells as it went. His brain was just quick enough at rewiring that it didn't kill him outright or leave him permanently seizing or in a vegetative state (as with the other half of patients with hydrocephalus this bad). We should be studying him to learn why his brain was able to keep up with the strain where others aren't.
    - api 11y ago
      Interesting, and I generally agree, but the parent post could easily be interpreted as "there's nothing to see here, we already know everything, so no need to look into it."
deleted 11y ago
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sirsar 11y ago
Well, we know that the outside of the brain uses more energy (by volume) than the inside. Plus, the evolutionary advantage of the wrinkles in the brain seems to be to increase surface area (of the outside, of course). Disclaimer: I'm no neuroscientist but I did take an introductory psych course this one time.
- innocentoldguy 11y ago
  Interesting you say that. My wife always claims I have a brain, but it is free of wrinkles. She's probably right.
- jacquesm 11y ago
  Thermal and wire-length constraints drive optimization toward that particular configuration. For instance if you're going to make a highly connected multiple-cpu computer it helps to keep the wiring as short as possible and the 'hot' parts on the outside (so they can cool). The most striking example of this design is the old CRAY machines. https://en.wikipedia.org/wiki/Cray-1 https://en.wikipedia.org/wiki/Cray-1

dahart 11y ago

I have a friend working on the Connectome project (http://cbs.fas.harvard.edu/science/connectome-project http://cbs.fas.harvard.edu/science/connectome-project) who told me last summer that all brain logic happens in the outer millimeter of tissue, everything inside is essentially routing. I'm summarizing his summary, so I'm certain it's more complex than that, but to a first order approximation, I'd guess your guess is correct! And so it wouldn't be particularly surprising that someone with cavities in their brain could be smart. One might expect deficiencies of some sort, but one might be speculating; I probably wouldn't bet on it.

mistaken 11y ago
This might even be useful for simulating brains, since the hollow brain model seems to be a lot simpler than a fully connected one.
amelius 11y ago
Uhm, but why isn't the routing essential for processing? And why is it there in the first place? In other words, why wouldn't evolution eliminate this costly and unnecessary part of the brain?
- trhway 11y ago
  it was mentioned that the condition develops gradually from the normal brain. So it seems pretty plausible that in some people the brain successfully rewires in parallel with and in response to the development of the condition so that direct white matter connections get functionally replaced by some kind of mesh-style network in the gray matter layer. While this may suggest that typical amount of white matter may be not strictly necessary, the significantly less than 100% success rate of such rewiring may explain why evolution hasn't gone this way .
  - rayedearthstar 11y ago
    This is quite unconvincing: the evolutionary advantage of, let's say, all animals the size of lemurs, having human level intelligence is such that pressure to find this rewiring would have been unprecedented. I think more data and research is needed here. My feeling is that when a few dozen of such cases are closely studied, interesting patterns will emerge. It is surprising that these cases exhibit high IQ and no immediate signs of dysfunction, but it would be absolutely extraordinary if no patterns of difference vs. typical brain were found at all.
    - ZenPsycho 11y ago
      evolutionary trees are littered with branches that have thus far been unable to overcome local maxima- Our eyes' retinas for instance, have optic nerves that connect on the light sensitive surface, blocking a huge portion of valuable photons, instead of the logical place to connect them- on the REAR of the retina- as squid and octopus retinas have been connected in their completely independent eye evolution. Once something works "good enough" there's not really any selective pressure to eliminate obvious design flaws if they don't particularly impede reproduction or survival.

redwood 11y ago

Or that the vital bits relocate to the spinal column

deleted 11y ago

[deleted]

api 11y ago
If all that tissue is not needed, then why did evolution conserve it? It consumes energy, adds size, and increases weight and head size which reduces agility. I really dislike "Chief Wiggum skepticism" that likes to just hand wave away and cheaply dismiss amazing things that might teach us a lot.
- deleted 11y ago
  [deleted]
- awalton 11y ago
  > If all that tissue is not needed, then why did evolution conserve it? We don't need two kidneys, two lungs, most of our liver, arms, legs, two eyes, ears, etc. These things just make us better at surviving - more likely to make it out of childhood and to an age where we can reproduce. Turns out, we don't quite need all that matter in our heads either, it just makes it more likely we'd survive some traumatic brain injury. If this guy experienced a TBI with this little brain tissue, there's probably no chance of any meaningful recovery left. Meanwhile we see non-diseased brains recover from injuries that look immediately fatal, like having spikes driven completely through skulls. What we've known is that our bodies are remarkably resilient to many kinds of injuries. This just extends what we know of our resiliency to this class of injury. It's also important to realize that hydrocephalus like this is a "small damage over time" type of injury usually - this patient didn't go to sleep with most of his brain matter intact and wake up with it gone, it was gradually lost over months or even years during his childhood as csf slowly increased in volume, obliterating cells as it went. His brain was just quick enough at rewiring that it didn't kill him outright or leave him permanently seizing or in a vegetative state (as with the other half of patients with hydrocephalus this bad). We should be studying him to learn why his brain was able to keep up with the strain where others aren't.
  - api 11y ago
    Interesting, and I generally agree, but the parent post could easily be interpreted as "there's nothing to see here, we already know everything, so no need to look into it."

deleted 11y ago

[deleted]

sirsar 11y ago

Well, we know that the outside of the brain uses more energy (by volume) than the inside. Plus, the evolutionary advantage of the wrinkles in the brain seems to be to increase surface area (of the outside, of course). Disclaimer: I'm no neuroscientist but I did take an introductory psych course this one time.

innocentoldguy 11y ago
Interesting you say that. My wife always claims I have a brain, but it is free of wrinkles. She's probably right.
jacquesm 11y ago
Thermal and wire-length constraints drive optimization toward that particular configuration. For instance if you're going to make a highly connected multiple-cpu computer it helps to keep the wiring as short as possible and the 'hot' parts on the outside (so they can cool). The most striking example of this design is the old CRAY machines. https://en.wikipedia.org/wiki/Cray-1 https://en.wikipedia.org/wiki/Cray-1