8 ms·

This is pretty pie-in-the-sky stuff. Having studied spinal cord anatomy a bit, it seems to me that "full use" of the donor body is absolutely not an option. Cor

This is pretty pie-in-the-sky stuff. Having studied spinal cord anatomy a bit, it seems to me that "full use" of the donor body is absolutely not an option. Cord cross sections are similar on a gross level but when you get down to specific pathways and such, there's huge variation. And you can't just rely on natural mending processes and neural plasticity to make up the difference. I'm not saying we'll never have something like this, but the "cut the cord and put it on top of the other cord" method described here seems massively, massively naive, like pre-enlightenment level medicine.

dclowd9901 13y ago
Ability to control different parts of the body (assuming there is a connection) seems like it would be more a "software configuration" issue than a "hardware issue" (if such an analogy is at all appropriate). Are you saying that even if the connection is there, the brain can never learn to utilize it if it doesn't jibe with the way the brain "is"?
- Retric 13y ago
  The brain has zero software it's 100% hardware. Basically each neuron in the spine is independent and really long so a local cut breaks connections several feet from the break because the cells die. You can't fix things because unlike fiber optics or cable each side does not line up even in the original person let alone someone else.
  - lostlogin 13y ago
    It does remap functions as needed however - avoiding damaged areas.
  - enraged_camel 13y ago
    >>The brain has zero software it's 100% hardware. I'm not sure if we can say this with any level of certainty. If anything, the nature vs. nurture dichotomy could translate directly to hardware vs. software. What nature gives you is hardware, and what you learn is software.
    - skaevola 13y ago
      Nope, learning physically changes the brain. For example, learning to juggle will increase certain portions of their brain. [1] It's like running Crysis, and having your video card's capability increase, 1. http://www.plosone.org/article/info:doi/10.1371/journal.pone.0002669 http://www.plosone.org/article/info:doi/10.1371/journal.pone...
      - Zarel 13y ago
        Yes, and hard drives physically change when they're modified, too. I think it's more like installing Crysis, and having more of your hard drive devoted to Crysis than before.
        skaevola 13y ago
        Memories are stored in the hippocampus, the changes took place in the occipito-temporal cortex. I'm not a neuroscientist, but my understanding is that the changes were directly related to processing, not memory.
        Zarel 13y ago
        I'd imagine it's the difference between writing to executable code and writing to data files. It's still just the files inside the hard drives that's changed.
        devindotcom 13y ago
        No one knows where memories are "stored," if stored is the proper term. But it is not exclusively in the hippocampus, that much is certain. The hippocampal region is definitely important in the function of memory but it is not where memories are located, and it is doubtful that they are located in any one structure in particular.
        skaevola 13y ago
        Definitely true, but not really responsive to my point.
  - coldtea 13y ago
    >The brain has zero software it's 100% hardware. Not really. Well, only true in the sense that a PC has zero software, it's 100% hardware, because, after all, a magnetic disk or a SSD is hardware too.
- devindotcom 13y ago
  In the brain, the hardware is the software. (Kind of like an FPGA, if I'm not mistaken?) Neural plasticity, which is essentially the extent to which the software can be modified by reforging connections between neurons, has its limitations, both in magnitude and rate. If you cut off someone's hand and put a foot in its place, chances are you could get a little basic functions, but rewriting the area of the motor cortex corresponding to that hand takes a good long time and will likely never be complete. It's not inconceivable that the brain could successfully send an action potential all the way from the cortex to the tip of the toe in a new body, but the 'rewiring' that would need to take place to make it happen in concert with the million other neurons (and many times that number in connections and networks) necessary for basic control or locomotion is simply not feasible on this scale. Putting a new finger where an old finger was removed is hard enough, and the brain has enough trouble rewiring itself to make that halfway decent. Rewiring for a whole limb or body, to say nothing of all the viscera, I really just don't see happening without some kind of massive assistance on a nano level, stuff that's sci-fi for now.
  - waps 13y ago
    Also keep in mind that your brain does not learn the same things at the same age. When your brain first forms and starts operating (< 18 days after conception) it will start learning very fast relations. It learns about the high frequency components of the human body, presumably things like how the electrical signals for a touch look like, or what the carrier signals are for your eye and the like. This also results in very, very fast sleep-wake cycles. When you "wake up from nothingness" so to speak, the cycle is less than a second. By 2-3 months it's about 5 minutes, and as any parent will know and complain about, at birth it's 2-3 hours. Obviously it eventually synchronizes to the sun, but that takes more than a year. Then as you mature, the myelin sheath starts to grow, which "locks in" the high frequency stuff it's already learned. By the time you're born you've lost the ability to learn about events that takes less than 3-4 ms to complete. By the time you're twenty, it will be at about 50ms. This is why people who start learning a sport at 3-4 years at most effectively have an insurmountable advantage. This has all sorts of effects that you will recognize in a growing human being. Short-term memory starts using progressively longer frequency signals to store itself. Reaction speed for anything new goes down (reflexes, and trained behaviors learned earlier stay in force though). Your ability to reason about things far away massively increases (a 4 year old kid cannot plan more than 20 minutes or so ahead without adult help, which mostly consists of reminding them what they were doing every 10 minutes or so). Furthermore the way your brain compresses signals is by distributing itself. There are small parts of your brain everywhere in your body, and several big blobs in your head. Every muscle has a cluster of neurons on it, and things like the heart, bigger muscles (like stomach muscles, biceps, triceps, ...) have large clusters on them. Those are clusters that do the same learning process as the rest of your brain, they're not preprogrammed. So your brain does not directly control your body, it negotiates what should be done with those local clusters. Because of this your body is able to have very short feedback loops controlling your muscles despite the fact that the decision process itself takes tens of milliseconds (and happens 1-2 meters away from the actual muscle). Now these clusters start out as blank as the rest of your brain, but they grow together, and they learn to communicate together. Different people send signals differently (well, the basic structure of the signal is the same, the semantic meaning, such as which muscle it affects, what timeframe it's talking about, ... is not). This is why if you connect a robot arm to a human, they cannot use it for fine motor control, even after months of practice, it improves to a pretty pathetic level, and just doesn't improve further (certainly not enough to write at normal size with it). If you want to be pedantic, there is more than one level of indirection. The first is the "brain region" -> spinal cord interface, and then every 15 cm or so in your spinal cord is another layer of control, and every point where neurons split up is another control point. Here's a rather basic introduction : http://en.wikipedia.org/wiki/Motor_control#Sensorimotor_feedback http://en.wikipedia.org/wiki/Motor_control#Sensorimotor_feed... All this means that your brain's lower level body control is effectively a ROM by the time you've grown up, and it is very dependant on tiny variations in the length of neurons to various parts of your body. Every single human body has a custom protocol for controlling the muscles that's different from everyone else's (so it's not possible, like in the movies, to mount something on the spinal column and take over motor control). Connecting up a brain to a new body, assuming you can keep it stable until the person wakes up, will immediately lead to a seizure (because the brain will be sending wrong signals to the heart), extremely rapid breathing, violent convulsions, ... until the patient is dead.
- agumonkey 13y ago
  I wonder if the nerve subsystem is generic at all. My bet is that genetic differences, life experiences and brain storage~ will be far too coupled for connecting two different bodies and expecting it too work. But I just remembered that there has been successful hand transplants so I'll just take the door.
- fumar 13y ago
  My sister has a brain tumor. They attempted to surgically remove the tumor, it rests at the base cerebellum, where it meets the spinal cord. In order to do this surgery, they had to cut a piece of her spine and in the process cut some nerve pathways. Post surgery, she still has trouble walking and other general motor skills. The brain is the software and hardware, any changes to it will alter its software.
smosher 13y ago
And you can't just rely on natural mending processes and neural plasticity to make up the difference. I wonder about that. I can see healing and plasticity going a very long way over time, but intuition is telling me there's not enough plasticity in the wiring of critical autonomic functions.
- devindotcom 13y ago
  It goes pretty far, and it is amazing, but the limitations are real and are encountered even on seemingly "simple" transplants like a finger. Critical autonomic functions, actually, may work fine, because they are more self-contained - the heart regulates itself, the gut in many ways as well, and many actions like breathing and basic drives are, to my knowledge, rather "standardized" between humans in the lower part of the brain. That's why we all have similar reactions to touching something hot or sharp, being hungry, out of breath, etc.
- kghose 13y ago
  Did you get down voted for voicing an opinion about a non-political, scientific topic? Only among nerds...
  - sp332 13y ago
    smosher got downvoted because intuition is not helpful here. We can sit around and talk about what we feel might be an answer, but if we don't have any information, it's just random noise.
    - smosher 13y ago
      I have a good bit of information about neurology, and that's exactly what my intuition draws from. I am extremely thankful I don't have the attitude you're endorsing.
petegrif 13y ago
This guy is a neuroscientist so presumably he has given this question some thought and I would imagine he too has 'studied spinal cord anatomy a bit.'
- jessriedel 13y ago
  There are plenty of crazy doctors out there who make nutzo claims not backed up by evidence in their field. One neuroscientist chosen at random is probably reasonable and competent, but a neuroscientist chosen conditional on publishing an astounding claim that isn't shared by any of his colleagues is almost certain to be cray.
snorkel 13y ago
Good point. I imagine the spinal cross connecting step would have to be preceded by some careful electrical probing and labeling of which spinal pathways are connected to which nerve endings.
- devindotcom 13y ago
  Yes, but unfortunately our microelectrodes are nowhere near good enough for this kind of thing. The bleeding edge is the arrays being implanted in retinas and visual cortex for prosthetic vision, and they're like a couple orders of magnitude too bulky and imprecise to be effective.
  - bennyg 13y ago
    As a person who had retinal detachment and ended up being blind in one eye, this is what I'm hoping for within about ten years. A way to get to my depth perception back would be great.

dclowd9901 13y ago

Ability to control different parts of the body (assuming there is a connection) seems like it would be more a "software configuration" issue than a "hardware issue" (if such an analogy is at all appropriate). Are you saying that even if the connection is there, the brain can never learn to utilize it if it doesn't jibe with the way the brain "is"?

Retric 13y ago
The brain has zero software it's 100% hardware. Basically each neuron in the spine is independent and really long so a local cut breaks connections several feet from the break because the cells die. You can't fix things because unlike fiber optics or cable each side does not line up even in the original person let alone someone else.
- lostlogin 13y ago
  It does remap functions as needed however - avoiding damaged areas.
- enraged_camel 13y ago
  >>The brain has zero software it's 100% hardware. I'm not sure if we can say this with any level of certainty. If anything, the nature vs. nurture dichotomy could translate directly to hardware vs. software. What nature gives you is hardware, and what you learn is software.
  - skaevola 13y ago
    Nope, learning physically changes the brain. For example, learning to juggle will increase certain portions of their brain. [1] It's like running Crysis, and having your video card's capability increase, 1. http://www.plosone.org/article/info:doi/10.1371/journal.pone.0002669 http://www.plosone.org/article/info:doi/10.1371/journal.pone...
    - Zarel 13y ago
      Yes, and hard drives physically change when they're modified, too. I think it's more like installing Crysis, and having more of your hard drive devoted to Crysis than before.
      - skaevola 13y ago
        Memories are stored in the hippocampus, the changes took place in the occipito-temporal cortex. I'm not a neuroscientist, but my understanding is that the changes were directly related to processing, not memory.
        Zarel 13y ago
        I'd imagine it's the difference between writing to executable code and writing to data files. It's still just the files inside the hard drives that's changed.
        devindotcom 13y ago
        No one knows where memories are "stored," if stored is the proper term. But it is not exclusively in the hippocampus, that much is certain. The hippocampal region is definitely important in the function of memory but it is not where memories are located, and it is doubtful that they are located in any one structure in particular.
        skaevola 13y ago
        Definitely true, but not really responsive to my point.
- coldtea 13y ago
  >The brain has zero software it's 100% hardware. Not really. Well, only true in the sense that a PC has zero software, it's 100% hardware, because, after all, a magnetic disk or a SSD is hardware too.
devindotcom 13y ago
In the brain, the hardware is the software. (Kind of like an FPGA, if I'm not mistaken?) Neural plasticity, which is essentially the extent to which the software can be modified by reforging connections between neurons, has its limitations, both in magnitude and rate. If you cut off someone's hand and put a foot in its place, chances are you could get a little basic functions, but rewriting the area of the motor cortex corresponding to that hand takes a good long time and will likely never be complete. It's not inconceivable that the brain could successfully send an action potential all the way from the cortex to the tip of the toe in a new body, but the 'rewiring' that would need to take place to make it happen in concert with the million other neurons (and many times that number in connections and networks) necessary for basic control or locomotion is simply not feasible on this scale. Putting a new finger where an old finger was removed is hard enough, and the brain has enough trouble rewiring itself to make that halfway decent. Rewiring for a whole limb or body, to say nothing of all the viscera, I really just don't see happening without some kind of massive assistance on a nano level, stuff that's sci-fi for now.
- waps 13y ago
  Also keep in mind that your brain does not learn the same things at the same age. When your brain first forms and starts operating (< 18 days after conception) it will start learning very fast relations. It learns about the high frequency components of the human body, presumably things like how the electrical signals for a touch look like, or what the carrier signals are for your eye and the like. This also results in very, very fast sleep-wake cycles. When you "wake up from nothingness" so to speak, the cycle is less than a second. By 2-3 months it's about 5 minutes, and as any parent will know and complain about, at birth it's 2-3 hours. Obviously it eventually synchronizes to the sun, but that takes more than a year. Then as you mature, the myelin sheath starts to grow, which "locks in" the high frequency stuff it's already learned. By the time you're born you've lost the ability to learn about events that takes less than 3-4 ms to complete. By the time you're twenty, it will be at about 50ms. This is why people who start learning a sport at 3-4 years at most effectively have an insurmountable advantage. This has all sorts of effects that you will recognize in a growing human being. Short-term memory starts using progressively longer frequency signals to store itself. Reaction speed for anything new goes down (reflexes, and trained behaviors learned earlier stay in force though). Your ability to reason about things far away massively increases (a 4 year old kid cannot plan more than 20 minutes or so ahead without adult help, which mostly consists of reminding them what they were doing every 10 minutes or so). Furthermore the way your brain compresses signals is by distributing itself. There are small parts of your brain everywhere in your body, and several big blobs in your head. Every muscle has a cluster of neurons on it, and things like the heart, bigger muscles (like stomach muscles, biceps, triceps, ...) have large clusters on them. Those are clusters that do the same learning process as the rest of your brain, they're not preprogrammed. So your brain does not directly control your body, it negotiates what should be done with those local clusters. Because of this your body is able to have very short feedback loops controlling your muscles despite the fact that the decision process itself takes tens of milliseconds (and happens 1-2 meters away from the actual muscle). Now these clusters start out as blank as the rest of your brain, but they grow together, and they learn to communicate together. Different people send signals differently (well, the basic structure of the signal is the same, the semantic meaning, such as which muscle it affects, what timeframe it's talking about, ... is not). This is why if you connect a robot arm to a human, they cannot use it for fine motor control, even after months of practice, it improves to a pretty pathetic level, and just doesn't improve further (certainly not enough to write at normal size with it). If you want to be pedantic, there is more than one level of indirection. The first is the "brain region" -> spinal cord interface, and then every 15 cm or so in your spinal cord is another layer of control, and every point where neurons split up is another control point. Here's a rather basic introduction : http://en.wikipedia.org/wiki/Motor_control#Sensorimotor_feedback http://en.wikipedia.org/wiki/Motor_control#Sensorimotor_feed... All this means that your brain's lower level body control is effectively a ROM by the time you've grown up, and it is very dependant on tiny variations in the length of neurons to various parts of your body. Every single human body has a custom protocol for controlling the muscles that's different from everyone else's (so it's not possible, like in the movies, to mount something on the spinal column and take over motor control). Connecting up a brain to a new body, assuming you can keep it stable until the person wakes up, will immediately lead to a seizure (because the brain will be sending wrong signals to the heart), extremely rapid breathing, violent convulsions, ... until the patient is dead.
agumonkey 13y ago
I wonder if the nerve subsystem is generic at all. My bet is that genetic differences, life experiences and brain storage~ will be far too coupled for connecting two different bodies and expecting it too work. But I just remembered that there has been successful hand transplants so I'll just take the door.
fumar 13y ago
My sister has a brain tumor. They attempted to surgically remove the tumor, it rests at the base cerebellum, where it meets the spinal cord. In order to do this surgery, they had to cut a piece of her spine and in the process cut some nerve pathways. Post surgery, she still has trouble walking and other general motor skills. The brain is the software and hardware, any changes to it will alter its software.

smosher 13y ago

And you can't just rely on natural mending processes and neural plasticity to make up the difference. I wonder about that. I can see healing and plasticity going a very long way over time, but intuition is telling me there's not enough plasticity in the wiring of critical autonomic functions.

devindotcom 13y ago
It goes pretty far, and it is amazing, but the limitations are real and are encountered even on seemingly "simple" transplants like a finger. Critical autonomic functions, actually, may work fine, because they are more self-contained - the heart regulates itself, the gut in many ways as well, and many actions like breathing and basic drives are, to my knowledge, rather "standardized" between humans in the lower part of the brain. That's why we all have similar reactions to touching something hot or sharp, being hungry, out of breath, etc.
kghose 13y ago
Did you get down voted for voicing an opinion about a non-political, scientific topic? Only among nerds...
- sp332 13y ago
  smosher got downvoted because intuition is not helpful here. We can sit around and talk about what we feel might be an answer, but if we don't have any information, it's just random noise.
  - smosher 13y ago
    I have a good bit of information about neurology, and that's exactly what my intuition draws from. I am extremely thankful I don't have the attitude you're endorsing.

petegrif 13y ago

This guy is a neuroscientist so presumably he has given this question some thought and I would imagine he too has 'studied spinal cord anatomy a bit.'

jessriedel 13y ago
There are plenty of crazy doctors out there who make nutzo claims not backed up by evidence in their field. One neuroscientist chosen at random is probably reasonable and competent, but a neuroscientist chosen conditional on publishing an astounding claim that isn't shared by any of his colleagues is almost certain to be cray.

snorkel 13y ago

Good point. I imagine the spinal cross connecting step would have to be preceded by some careful electrical probing and labeling of which spinal pathways are connected to which nerve endings.

devindotcom 13y ago
Yes, but unfortunately our microelectrodes are nowhere near good enough for this kind of thing. The bleeding edge is the arrays being implanted in retinas and visual cortex for prosthetic vision, and they're like a couple orders of magnitude too bulky and imprecise to be effective.
- bennyg 13y ago
  As a person who had retinal detachment and ended up being blind in one eye, this is what I'm hoping for within about ten years. A way to get to my depth perception back would be great.