The Trouble With Head Transplants

By Andrew Jackson, Newcastle University | February 2, 2016 1:06 pm
head

(Credit: Taveesak Pansang/Shutterstock)

In a 1978 essay, titled Where Am I?, the philosopher Daniel Dennett suggested that the brain was the only organ of which it’s better to be a transplant donor than recipient. Now Italian neurosurgeon Sergio Canavero wants to turn philosophical thought experiments into reality by transplanting the head of Valery Spiridonov, who suffers from a debilitating muscle wasting disease, onto the healthy body of a dead donor.

Beside posing questions about personal identity, there are more prosaic challenges that must first be overcome. The brain would have to be kept alive during surgery by cooling it to 10-15°C, and the immune system would need to be powerfully suppressed to prevent transplant rejection. But the greatest hurdle may be how to restore connections to the spinal cord. Without this connection the brain would have no control of its new body.

In 1970, Robert White at Case Western Reserve University performed a head transplant using monkeys. Without spinal connections the animal was paralyzed from the neck down for the brief time it could be kept alive.

Canavero believes the time is right to revisit this controversial procedure, due to recent advances in surgical techniques and scientific understanding. He hopes that his “GEMINI” protocol – combining polyethylene glycol to fuse nerves with electrical stimulation of spinal circuits – will allow his patient to move and even walk following the procedure.

Breakthrough or Spin?

Canavero has been criticized for publicizing his ideas in the media before releasing peer-reviewed research papers. Only time will tell whether promised experimental results are forthcoming. But, on the basis of current neuroscientific understanding, does the proposal stack up?

Unlike many tissues in our body, the nerves of the spinal cord don’t spontaneously repair themselves after damage. And despite regular media reports hailing new breakthroughs, currently there is no effective cure for the millions of people paralyzed by spinal cord injuries each year.

Polyethylene glycol is among a growing list of treatments (including drugs, stem cells and gene therapies) showing promise in pre-clinical studies, but the path to real-world applications is notoriously tricky.

Experiments in animals such as rats and mice are essential to developing new therapies, but important differences must be borne in mind when extrapolating to human treatment. Given sufficient retraining, rodents – even with completely severed spinal cords – can learn to walk again, because much of their circuitry for locomotion is located below the injury.

In contrast, the brains of primates such as monkeys and humans are more directly involved in guiding movements. As a result, the recovery experienced by people with complete spinal injuries is much more limited.

For those that live with spinal cord injuries, there are some reasons for cautious optimism. A US trial of epidural stimulation is reporting impressive results using a small pacemaker-like device to send electrical signals into the spinal cord. Participants in the trial have been able to move their legs and even support their own weight while standing.

The mechanisms underlying these improvements are not well understood, but stimulation seems to reawaken the spinal cord and may allow it to respond to residual connections from the brain that have survived injury. More speculatively, it may in future be possible to control stimulation directly from electrical signals recorded from the brain using brain-computer interface technology.

Although epidural stimulation is a promising line of research, it is being trialled in a select group of patients and is still far from a magic cure. So, if we can’t yet mend an injured spinal cord, what hope do we have for joining the brain to an entirely new body?

The Capacity for Rewiring Is Not Limitless

While most spinal injuries are caused by traumas that bruise or tear the nerves, a transplant surgeon could sever the cord cleanly with a scalpel blade. But weighed against this small advantage is the staggering complexity of joining two separate neural circuits that have neither developed nor functioned together before.

Even if the spinal cord could be reconnected, would the patient ever learn to control the new body? The brain has a remarkable capacity for rewiring itself, especially as we develop during childhood. But the “plasticity” of the adult brain has limitations.

Many amputees experience vivid and often agonizingly painful “phantom” sensations from where a lost limb used to be, even years after amputation. This suggests that our mental representation of ourselves – our body schema – may not easily adjust to changes in our own bodies, let alone get used to someone else’s entirely.

Perhaps transplant tests with monkeys may in future provide convincing support for applying this surgery in patients, although such experiments would certainly not be allowed by the strict regulations that govern animal research in the UK. Nor should they be at present, given the severity of the procedure and slim chance of success.

The media love stories about maverick scientists fighting the establishment. But science most often progresses in careful, incremental steps that are published and scrutinized in peer-reviewed journals. The philosophers can speculate whether it is better to be the donor or recipient of a brain transplant. But as a neuroscientist, until we have the technology to reconnect the spinal cord, neither is an appealing prospect in reality.

(This article was originally published on The Conversation. Read the original article.)

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  • Har Sukhdeep Singh

    My questions are;
    Is there a serious death of human beings that we want to make all ‘Is’ live longer than their bodies?
    Isn’t fresh life is far better than aged?
    If life has been sustained on earth for centuries then it should be allowed to follow time tested system than forcing it to go through new ideas at huge expenses for no good reason except allowing someone getting high of his/her achievement?
    Har Sukhdeep Singh

    • Emkay

      huh? what? really? you’re kidding!

    • Jason Allen

      With age comes wisdom.
      If the truly brilliant can continue to live on far past their normal life expectancy, it could greatly benefit mankind.
      It wouldn’t have any impact on young people making their own contributions to the world.

      • Har Sukhdeep Singh

        Nature, our limits to so called knowledge n wisdom, has never bothered about the both and let a system/process self sustaining and evolving, move in time on itself. what men n women of knowledge/wisdom are doing may be the part of the same to evolve into inorganic evolution but that is a far cry. mankind can live better and let other life live in better conditions if undesirable ‘progress’ can be reined well. we do not need progress; we need freedom from the huge negativities like greed,wars,crimes, abuse of resources, uncalled for commerce etc.
        you can say I m wise n intelligent and also playing in the hands of Nature as much as the others who gave ideas in lost centuries to get into the rat race of energy consumption and creation of waste.
        I believe all other life forms must create a revolution against the nonsense mankind does in the name of progress. pl do comment again on my views.

        • toomanycrayons

          “toomanycrayons>Har Sukhdeep Singh 2 days ago

          [Pending]”

          Anybody home @The Crux? Maybe the head transplant(s) didn’t take?

        • toomanycrayons

          I wonder…if breaking it up will make any difference:

          ‘”If life has been sustained on earth for centuries then it should be

          allowed to follow time tested system than forcing it to go through new

          ideas at huge expenses for no good reason except allowing someone

          getting high of his/her achievement?”-Har Sukhdeep Singh

          Since when did life/Nature not include us? Does “life” like anything? Does life even matter? It seems rather presumptuous, as well, for your un-transplanted head to be pontificating on its own relative merits
          while 1.3 billion year old gravity waves rumble through us. Clearly we
          are only briefly observers, and seldom the issue, no matter how many we re-present through our urgent [urges] and [fluid] conceits.’

        • toomanycrayons

          The Crux doesn’t seem to like links, so the middle bit may never show up. Here’s the end. Not much reason to bother anymore, really. Good Luck with this site.

          “toomanycrayons Har Sukhdeep Singh • 4 minutes ago
          Hold on, this is waiting to be approved by The Crux.” Really?

          “Nature,

          our limits to so called knowledge n wisdom, has never bothered about

          the both and let a system/process self sustaining and evolving, move in

          time on itself. what men n women of knowledge/wisdom are doing may be

          the part of the same to evolve into inorganic evolution but that is a

          far cry….”-Har Sukhdeep Singh

          You keep invoking the prospect of a

          detach viewer while commenting on your/our lack of detachment from the

          process you call,”Nature.” Inorganic evolution: Is that like talking

          for the sake of talking? What might be the evolutionary benefits of

          organics becoming inorganic, and how exactly would the selection process

          work; what happens to your observing self then? You type therefore you

          exist, for now? (w/apologies to René.) You are simply imaging a “You”

          perspective which transcends the inevitable. Shall your “consciousness”

          spandrel set you free? Never stop typing…and, find out.

        • toomanycrayons

          Well, the jury still seems to be out. Maybe the problem is the link. Here’s the quote w/o the link, I’ll add that separately:

          “Long

          ago, deep in space, two massive black holes—the ultrastrong

          gravitational fields left behind by gigantic stars that collapsed to

          infinitesimal points—slowly drew together. The stellar ghosts spiraled

          ever closer, until, about 1.3 billion years ago, they whirled about each

          other at half the speed of light and finally merged. The collision sent

          a shudder through the universe: ripples in the fabric of space and time

          called gravitational waves. Five months ago, they washed past Earth.

          And, for the first time, physicists detected the waves, fulfilling a

          4-decade quest and opening new eyes on the heavens.”

  • Overburdened_Planet

    The philosophers can speculate whether it is better to be the donor or recipient of a brain transplant.

    Seems like neither would be the case.

    Phantom pain, suppressed immune system, no guarantee of mobility.

  • Lee Krystek

    Didn’t McCoy do this for Spock in the 3rd Season of ST TOS after aliens stole his brain? Of course it was easier as he only had to restore it to Spock’s body. No rejection problems!

  • Pro

    THE trouble? Is everyone in agreement that the soul is in the body and the body receives the head not the head that receives the body?

  • Pro

    THE trouble? Is everyone in agreement that the soul is in the body and the body receives the head not the head that receives the body? It doesn’t matter? Really? The head has to know it’s letting go of soul and the practitioner has to have his attention on the soul of the body.

  • Pro

    come on you god and atheist freaks… if the soul wasnt in the body then we’d be able to keep heads alive. Besides that I’m working on soul birthdays in previous astrological signs.

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