Canadian conjoined twins share brain connection—and experience

November 10, 2017 • 1:15 pm

These 11-year-old conjoined twins, Krista and Tatiana Hogan, are joined at the head, and, not only that, share part of their brains. As The Walrus reports (in a somewhat hyperventilating article), they each have a brain, but there’s a neural bridge between the thalamus of each brain (the part of the brain that relays sensory signals and is important in consciousness). This apparently makes them share each other’s sensations, so that what one sees or tastes is at least partly shared with the other. When one body is tickled, the other twin laughs. There’s even a shared mental connection—some sharing of thoughts, and we can’t conceive of what that’s like. Nobody else in the world, nor any pair of twins, has this kind of cerebral connection.

They weren’t expected to survive, and even if they did they were expected to be in a vegetative state. They’ve defied those expectations, but aren’t in fantastic health: one has heart problems because she pumps blood to her twin’s brain, and they also have epilepsy and slowed intellectual development. Still, they’re doing pretty well given the situation.

Here’s a 45-minute CBC documentary made when the twins were seven: an absolutely fascinating look at a neurological anomaly, but also at the resilience of two girls in the face of an inoperable condition. They’ll be head to head for life. (If one of them dies, the other will follow shortly). It’s also a one-off opportunity to study the transfer of experience, but of course if you were the parent, or the girls, would you want them probed and examined by a bunch of scientists?

As The Walrus says, this raises questions about what “self” means, but that’s a bit of an exaggeration. The real question is “how is one’s sense of being a ‘self’ modified when your brain is connected to another brain?”

This is a great documentary, and if you have a spare 45 minutes, I recommend that you watch it. Seriously. Some might think they’d be grossed out by this, but give it a try. I was heartened and fascinated, and there’s a fair bit of science in there, too.

h/t: Allison

18 thoughts on “Canadian conjoined twins share brain connection—and experience

  1. Just saw this last night. It’s truly an incredible story. Although their lives are unbelievably difficult, I can’t help but think of them as superheroes in a way too. They experience so much that no one else on the planet will ever be able to.

  2. This would seem to put to rest the claims of mysterians that one person can’t know that another person is not a zombie.

  3. (Typo alert:”one has heart problems because she pumps heart to her twin’s brain”)

    Amazing story (about sharing sensations and thoughts.) I’ve sometimes wondered about this case:

    The bonus head is said to have been able to blink and smile–I wonder if the head had been left attached (and if both lived–the “main” child later died of an infection) would it have been able to be a conscious, thinking person (and how weird would that have been?) I don’t think that I considered the possibility of sharing thoughts, though.

    1. Oh, my. I look at that extra head and see it as more like another human than a “parasite,” though of course it really wasn’t.

      And yet…

  4. I’m way too weak and emphatic, I cannot watch it. I would read about it, but watching the documentary is too sad for me.

    I looked for a bit at the actual girls only. Does anybody *feels* strange in the head just at the thought of two/one shared brain(s)?
    Maybe that’S what @jerrycoyne meants when he says “grossed out”.

  5. So cute. The twin who can’t stand the taste of ketchup is a kindred spirit. I don’t use the word “spirit” but that would be me. This wasn’t hard to watch mainly because I have seen two conjoined twins with two legs but two heads (heads not shared) and also a documentary about a girl without a face. I’m particularly interested in this and the role of the thalamus in self and “consciousness”. When the boy at the science museum rests his head on the one as they are on the merry-go-round thing- so, so adorable. All heart.

  6. It’s tragic. And no, I won’t watch because quite frankly it does freak me out.

    I have enormous sympathy for them and repulsion at the same time. Quite aside from the weirdness, the way in which they’re joined is a massive disability – they can never walk or do any other activity normally. The human skeleton wasn’t built to be contorted all the time, I would imagine that alone would lead to all sorts of aches and pains and difficulty with every activity that normally only paraplegics suffer.

    No kudos to whoever brought them into the world, though.


  7. Thanks for posting this. So fascinating how their brains are cross connected. Brain plasticity seems to have no bounds.
    The practicalities of their lives is fascinating but scary. How do they put on the slip on shirts? Watching them run makes us all worried for their necks!

  8. The documentary is very touching and shows a noble sense of attachment in the whole family and community. It’s heartwarming to see this play out. The mom shows deep devotion to the kids who appear to be very happy.
    Still, they were given the option of an abortion when the condition was detected. I would have opted for that. I have to weigh the pros and cons over the children’s lifetimes and I worry that the investment in time and energy to support them would be too much of a burden. I can imagine the situation could get difficult as the kids age.

  9. I don’t think it’s exaggerated to raise questions about what “self” means. There’s obviously a continuum between two heads and one, even if these twins are only a tiny way along that continuum.

  10. Extraordinary. Gives new meaning to solipsism and questions of identity, consciousnes, and the role of individual in society. I really enjoyed the neurological aspects and how doctors were exploring those behavioral connections. My kids both watched it and were riveted.

  11. Gosh no. Anyone put off by this strikes me as shallow in a distinctly unflattering, even distasteful, way. Not only is the unusual nature of their conjoined bodies fascinating, but their lives in many respects are a lot better than most “normal” people’s I’ve met. And who can deny that they’ve risen to the challenge?

    The sheer enthusiasm, robustness, and love on display is wonderful and special. The scientific value of their unique minds is a happy bonus. Not to forget how modern medical science has performed well in keeping them both healthy.

    I feel privileged for having seen this video. It’s that good.

    1. Personal favourite moment: the slide. There’s the fascinating insight that, as soon as one feels an emotion, the other feels it too. Then I love how they both progress from nervousness and fear to experimenting to actually enjoying the big slide. They’re so cute and charming!

    2. I worry about what happens when puberty strikes. What will they do if they experience normal sexual urges (by which I mean, strong desires; I do not mean cis-only). Right now they are not nearly as self-aware as they will be when they’re older.

      It is true, of course, that the original “Siamese Twins” eventually both had wives…

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