Conjoined twins with shared brains can pass sensory information to one another

Conjoined twins Tatiana and Krista Hogan share part of their brain, and, seemingly, can pass sensory impressions and thoughts between each other:

Adding to the conundrum, of course, are their linked brains, and the mysterious hints of what passes between them. The family regularly sees evidence of it. The way their heads are joined, they have markedly different fields of view. One child will look at a toy or a cup. The other can reach across and grab it, even though her own eyes couldn't possibly see its location. "They share thoughts, too," says Louise. "Nobody will be saying anything," adds Simms, "and Tati will just pipe up and say, 'Stop that!' And she'll smack her sister." While their verbal development is delayed, it continues to get better. Their sentences are two or three words at most so far, and their enunciation is at first difficult to understand. Both the family, and researchers, anxiously await the children's explanation for what they are experiencing.

A piece of their mind (via Kottke)

History of conjoined twins

I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.

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MrsBug

I wonder what happens when one is reading a book and the other is watching TV?
Stjohn

Awesome. If they’re separated, are they still entangled, sensoria linked like Christopher Hinz’s Paratwa?
Anonymous

Remember that scene in FREAKS where one conjoined twin is necking with her boyfriend while the other one is reading a book, and after a while the reader puts down her book and just shudders a bit in contact ecstasy? I guess that might be like that.
Anonymous

That. Is. So. Cool.
eviladrian

Is there any chance that they might be cuing each other with head movements or leaning towards things when one grabs an object that the other one sees?
fnc

Holy cow. If they really are individuals but can share thoughts (probably without much control, though they might learn that in time), would that count as working model of telepathy?

Imagine that, human beings who may have to learn how to keep someone else’s thoughts out of their consciousness. The world is more fascinating to me today than it was yesterday.
anansi133

A hive-mind of two.
Chrs

Evidence for the development, in the future, of effective brain-machine or brain-machine-brain interface.
- turn_self_off
  
  Reminds me of the description of telepath sex in babylon 5, where they would end up more or less as one being in mind.
  
  Hell, it gives all kinds of interesting/creepy fetish options. Transhumanity will be a weird place, thats for sure…
piminnowcheez

I was going to call bullshit on the whole thought-sharing business until I went to the article and read that there are connections between their thalami. That’s so unlikely that it’s hard to believe; usually the main problem with craniopagus is shared brain *vasculature* rather than shared brain tissue. But looking at all the coverage of the story I could find, it does seem like there’s some crossing white matter between the two.

I really wish I could see an MRI of their brains. I tried like crazy to find a case report on these girls but apparently their doctor didn’t write one (which is weird, because it would be an easy pub for him) and so the only descriptions of the neural tissue are coming from dumbed-down writeups in the general press.

I’m pretty astonished that they weren’t separated. Some of the press coverage I read suggested that the doctors thought they couldn’t be because of the shared brain tissue, but it’s hard for me to imagine what connections they could share that would be life-threatening to cut, and if you’re going to hack around in the brain, it’s MUCH better for long-term outcome to do it as early as possible when the developing brain is at its peak plastic potential.

Assuming they aren’t separated, it will be interesting to hear them describe their experience when they’re older, although, I sure as hell wouldn’t want to be them. That’s going to be a difficult life, albeit a unique one.
- Chrs
  
  Going into the thalamus is incredibly, incredibly complicated. You really can’t poke around in there much without basically severing the cortex from the body.
  
  Still, since people can get along with literally a missing hemisphere if it was early enough… in this case, I suspect “do no harm” took precedence.
  - piminnowcheez
    
    That’s why I wanted to see a picture of the scan – it’s not clear that they’d have to go *into* the thalamus, depending on the nature of the connection. It’s incredibly hard for me to imagine how they’d actually share thalamic tissue — they wouldn’t have such independently formed heads — but there might be an access point more superficially where the connecting fibers could be cut. But only their doctors know, I guess.
    
    I’m not sure that no harm was done… apparently the mother was given the option to terminate and declined. I don’t think I’d have made the same decision, but of course, it’s her right.
    - Major Variola (ret)
      
      @Mr Cheez
      I agree that the MRI would be very interesting and is key. A thalamic connection would be particularly weird –that’s attentional midbrain stuff.
      
      I wonder what their responses will be when they realize other people don’t have certain ‘internal dialogues’ that she does. “Don’t you normals feel lonely? Cut off?”
      
      An interesting question is what if the girls grow up and want their
      brain connections (but not body, which is probably not possible) cut.
      
      Very Phillip K. Dickian
      - Michael Smith
        
        Given the geometrical constraints I think an MRI is unlikely to be done.
      - Anonymous
        
        They have MRI machines that can accomodate the morbidly obese.
      - Ugly Canuck
        
        That was my thought precisely.
SpaceGhost

I’ve often wondered if you could (without killing them) divide a persons mind into 2 seperate parts what would the individuals experiance? People are so used to feeling like just themselves could one person become 2? Which half would you inhibit or would it be both? I think that all minds are touched by a single spirit and the reason we don’t feel it is only because of the seperation of space between us, nerves unable to connect to each other. This is kind of the reverse – 2 minds becoming one, though likely there remain 2 personalities so individuality remains. I hope they survive (many siamese don’t fare well), there’s a lot that could be learned from them.
- piminnowcheez
  
  What you describe is something like what the “split-brain” patients whose commissures (crossing fibers between the two hemispheres) were cut to treat intractable epilepsy (this procedure is no longer done). Sometimes the right and left sides would work at cross-purposes; the right hand unbuttoning a shirt while the left was trying to button it for instance. Unfortunately, only the left hemisphere gets to speak, so a description of these patients’ subjective experience was a bit one-sided.
lvdata

A hive-mind of two? It seems more like a well developed split personality. If they grew up being treated as ONE person they may not have had two personalities. I would suspect that you could see the same effect if you treated the left and right sides of a normal kid as 2 separate people, although that would be called child abuse. No way to ethically do those kind of experiments….
Major Variola (ret)

They need shirts that say, “I’m not photoshopped”
Anonymous

Just like The Octopus in The City of Lost Children!