Craniopagus Twins Share a Brain and See Out of Each Others Eyes

Take for example the case of people who have never seen from birth and are given sight through retinal implants; they can see colours and images and patterns but their brains can make no sense of the input - they sense no depth, shapes, relations between words and images, shadows meaning three dimensionality, etc. etc. that we all take for granted. Those neurones have been put to alternative use already and in some ways you really can't teach an old dog new tricks.

I’d imagine any such system would have a learning curve as each brain figures out the patterns but it seems there isn’t any fundamental difference that makes each person’s thoughts unintelligible.

(Granted, as siblings one could argue their thoughts would naturally tend toward being intelligible but it seems too early to know the answer to that question)

Similarly, we serialize our internal representations into language for - literally - serialization. It's for transmission, but also allows differing internal representations.

Is this accurate?

Also interesting: the one that controls more arms is the outgoing and high-strung one, while the one that controls more legs is the quieter and relaxed one. It seems unlikely that these facts are uncorrelated, though the causal relationship is anything but clear.

Incredibly, in an article full of pictures, they never actually tell you which twin is which and only address them as a unit of 'twins' in descriptions, which seems incredibly rude and depersonalizing to Krista and Tatiana. (Or, alternatively, never mention that the twins prefer to be spoken of as a unit -- which is itself an incredibly interesting fact.)

1. Each brain controls more limbs than usual, but brains are plastic and can learn do that. It seems they have separate "personalities" however and they recognize themselves as different persons. So they don't "control" each other's consciousness although they seem to be able to communicate thoughts (not clear how) can control the limbs of the other, and can see what the other sees (e.g. with closed eyes, they can see what the other girl sees). Whats fascinating is how one of them can manage to override the movement signals coming from the other. Surely further examinations during their life will show how action initiation/inhibition happens in their brain.

3) It seems no, they dont control a limb simultaneously. They seem to be able to cancel the signals from the other person, presumably because their personal signals are much stronger (possibly because they have learned over time to do that ) or they have developed some mechanism to inhibit sensory signals from the opposite brain. This may be happening already at the level of thalamus where they are connected. Since their arms can possibly be controlled by both brains through the thalamic connection, i wonder if they can train themselves to use primarily the opposite person's limb, e.g. hand. It might be possible since the wiring is already there - it seems to only require sensorymotor traning.

2) I suppose you mean they have some kind of learning problems. But not really, people can learn and have normal IQ with much much less brain than what they may be allocating to the opposite body. And it's not even clear that they do that. They essentially share a thalamus but not much else , and even so, they dont seem to have less total thalamic mass than they would have separated . Also , thalamus being a relay rather than a decision taking region, it doesnt seem it would affect their intelligence too much.

- http://ojs.library.ubc.ca/index.php/ubcujp/article/view/2521...

Seeing out of 3 eyes seems like a much stranger sensory system. It's not going to simply extend to a wider field of view because someone else is controlling the focus.

Indeed! The way I see it, identity derives from memory. So to the extent (if any) that they share identical memories they are strictly the same person. Beyond that I would guess there may be some (false) identification with behaviours of the other twin, in a manner redolent of Gazzaniga and Sperry's famous split brain experiment:

https://physics.weber.edu/carroll/honors/split_brain.htm

It shouldn't be hard to show only Tatiana a picture of a number/person/etc, ask her to think about it, and see whether Krista can tell.

Somehow it doesn't add up with the rest (shared motor abilities through the thalamus), and sounds more like the poetic but bogus claims that many twins make about one another.

My point: I don't believe you can extrapolate from "these girls can share thoughts" to "all human thought share the same protocol/mechanism." That said, we all have human brains, and maybe human brains share the same protocol/mechanism for thought.

Our ability to think is extremely adaptable. I doubt we all think alike (apart from the general mechanism and macro structures).

One old experiment was to completely flip someone's vision upside down (with mirrors in goggles). It generally took people a week or two to adapt, but then their brains could once again link their visual input with other sensory input. They clearly didn't have the same internal logic as others (since their brains had to reverse the image), but because they received constant feedback on the results of their logic, their brains made them understand the world the same way everyone else does.

My wife and I were discussing that aspect just this morning as we discuss the young ladies in this article, what with Chang and Eng not letting it slow them down much. Given the age of the girls I find it a bit creepy to contemplate, but I’m curious what other pieces of anatomy are wired to both brains.

Hopefully they work it out, and I suspect they will. I’m confident that the lives of Chang and Eng were not roses and unicorns, but if a couple of Asian guys can make a life for themselves in North Carolina in the 1800s, and conjoined twins to boot, I thinks these girls have a good shot.

As a side note, “Siamese Twins” might be out of favor, but the term originates with Chang and Eng, who were from Thailand, formerly known as Siam.

Do you mean anything in particular for this, or are you appropriating a TV show phrase to mean "unusual"?

(Just pointing out that the 'central finite curve' is something that has meaning to Ricks but isn't really a stand in for 'usual' in any meaningful sense in the context of the TV show -- I'd hate for what's potentially a cool sci-fi idea to turn into a euphemism for "the shell of a high dimensional normal distribution".)

The true mother nature's plan was probably killing the mother and both girls at birth time. I would thank the obstetrician at charge and his/her team instead.

I can also read your thoughts. Are we the same person? The only difference is you need to put them in text, and she does it via electrical impulses.

Their thoughts are not integrated into a single entity, but rather they are able to communicate via a channel you don't posses. As evidence, when they need to share thoughts it takes them extra time, to me that means communication, not single entity.

Another way to put it: They can distinguish their own thoughts from those of their sister.

> am resident in Neurology

Then you should know that even a regular brain is really multiple independent "thinkers" that are wired to give the illusion of a single entity. Disrupt that wiring and the different "minds" will do their own thing, separately from the others (alien hand syndrome for example).

And I know that that sounds like an argument against what I'm saying.

It's basically the question of consciousness: Who is the "I" that is speaking. That alien hand has no consciousness. These conjoined sisters have two, because each can perceive itself as distinct.

Because the system isn't well-defined in this case, which happens less than 1 in a million times, so isn't worth trying to fix explicitly.

The simplest solution is to give them two identities and move on with life having a little oddity -- as a pragmatic solution, it seems like the one that would end in the least litigation, as it confers an advantage not a disadvantage on the person(s) in question and can't possibly disenfranchise anyone.

It's not like you can't already create extra 'selves' (in most senses; eg voting is different) legally at the cost of $200 a pop -- what does it really matter if less than 1 in a million people happens to have two for what is otherwise going to be a very hard and likely short life?

That said -- I agree with you that it's not really well-defined here, because our notion of 'identity' is already highly problematic.

Edit:

This is a strange thought: what is the impact on someone with multiple personalities if you allow each personality to incorporate an LLC, all owned by a parent LLC (obviously, all legally owned by the 'person') -- ie, create an external legal framework that parallels the structure of the internal mental one, that all of the personalities should be able to view?

I'm honestly not sure if that's helpful for providing a lens to see the interaction play out or harmful for legitimizing the split. (And to some degree, all of us possess such multiple personalities -- we're rarely entirely the same person at work as at home or church or... whatever. I'd just argue that 'healthy' adults understand the interaction better.)

All humans have difficulty living. We have to walk and eat and sleep and can't ever stop breathing or we'll die. These girls just have it different. Maybe harder but since they haven't experienced any different, they're probably not too fussed, just as we don't hope to avoid having to breathe all day long.