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Science Technology

When You Split the Brain, Do You Split the Person? (aeon.co) 124

An anonymous reader shares an article: The brain is perhaps the most complex machine in the Universe. It consists of two cerebral hemispheres, each with many different modules. Fortunately, all these separate parts are not autonomous agents. They are highly interconnected, all working in harmony to create one unique being: you. But what would happen if we destroyed this harmony? What if some modules start operating independently from the rest? Interestingly, this is not just a thought experiment; for some people, it is reality. In so-called 'split-brain' patients, the corpus callosum -- the highway for communication between the left and the right cerebral hemispheres -- is surgically severed to halt otherwise intractable epilepsy. [...] What, then, happens to the person? If the parts are no longer synchronised, does the brain still produce one person? The neuroscientists Roger Sperry and Michael Gazzaniga set out to investigate this issue in the 1960s and '70s, and found astonishing data suggesting that when you split the brain, you split the person as well. Sperry won the Nobel prize in medicine for his split-brain work in 1981. [...] Case closed? Not to me. [...] To try to get to the bottom of things, my team at the University of Amsterdam re-visited this fundamental issue by testing two split-brain patients, evaluating whether they could respond accurately to objects in the left visual field (perceived by the right brain) while also responding verbally or with the right hand (controlled by the left brain). Astonishingly, in these two patients, we found something completely different than Sperry and Gazzaniga before us. Both patients showed full awareness of presence and location of stimuli throughout the entire visual field -- right and left, both.
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When You Split the Brain, Do You Split the Person?

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  • by JohnFen ( 1641097 ) on Tuesday October 03, 2017 @09:43AM (#55301061)

    The brain is perhaps the most complex machine in the Universe

    That reminds me of an Emo Philips joke: I used to think the brain was the most amazing thing in the universe. Then I remembered what was telling me that.

  • by Anonymous Coward

    If you like this kind of stuff, read Phantoms in the Brain: Probing the Mysteries of the Human Mind by V. S. Ramachandran. Good book.

  • If a person has Dissociative Identity Disorder (Multiple Personality Disorder) we still see him as one person. Cutting a brain in half does not make a difference.
    There have been people where they lost half their brain. They do not become half a person. They are just the same person with, in some cases, a complete different mentality.

    So: leave it in the body, two people. Put it in two bodies: one person.

    If they are born with two brains and one body, it will be seen as two persons.
    These are pretty clear situa

    • Re: (Score:1, Insightful)

      by Anonymous Coward

      If a person has Dissociative Identity Disorder (Multiple Personality Disorder) we still see him as one person.

      But is that the smartest, most enlightening thing to do? Does looking at them instead of him tell you more information, the same, or less?

      Geez, I sometimes model people differently even without malfunctions quite like that happening. When my wife's on her period, there's a few days when she's unusually paranoid, hostile, desperately itching to turn any slightest adversity (e.g. that douchebag cut m

      • When my wife's on her period, there's a few days when she's unusually paranoid, hostile, desperately itching to turn any slightest adversity (e.g. that douchebag cut me off in traffic, or we ran out of half-and-half for the morning coffee, or someone at work didn't even try to figure out their problem) into a full-on fight, and she's generally evil.

        That's the time of the month, you spend more time with the side girlfriend who isn't on the rag.....

        You just gotta match them to make sure neither has period

    • If a person has Dissociative Identity Disorder (Multiple Personality Disorder) we still see him as one person..

      That's because DID is just one person with a fully connected but traumatized brain

      Cutting a brain in half does not make a difference.

      It absolutely does when you are severing the communications between those two halves, but leaving both perfectly functional.

      There have been people where they lost half their brain. They do not become half a person. They are just the same person with, in some cases, a complete different mentality.

      They have a different mentality because literally half of it has been severed - they really are a half/different person

    • by Jack9 ( 11421 )

      > we still see him as one person

      From a neurological perspective, this is a simplistic view. One personality, seems more appropriate.

      "A person is not a single entity of a single mind: a human is built of several parts, all of which compete to steer the ship of state." - David Eagleman
      Jordan Peterson has also said as much (I don't have the exact quote). I'm sure there's more than a handful of papers, to find, on the subject of personality composition.

      > Cutting a brain in half does not make a difference.

  • ...you kill the person. All other questions in this thought experiment are irrelevant and probably useless.
    • by JoshuaZ ( 1134087 ) on Tuesday October 03, 2017 @10:22AM (#55301371) Homepage
      This isn't a thought experiment though. We have actual split-brain patients and we can see how they react. I'm not sure why you think that this kills the patient either, since for most purposes, such patients act very similarly to how they did before the procedure.
    • by Anonymous Coward
      Nevertheless, the original question can be answered. When you split the brain, you do not necessarily split the person, but if you use a very sharp blade like that of a katana, chances are high that you will also split the person. You need to use a dull blade or saw and split the brain slowly in order to avoid splitting the person.
    • by gweihir ( 88907 )

      Your absolute judgement has no scientific basis in observable facts. Are you a religious fanatic?

  • I don't know much about the brain but I do know if you split peas you make soup.

  • by sinij ( 911942 ) on Tuesday October 03, 2017 @10:03AM (#55301227)
    Brain is more like multi-core CPU with dedicated special-purpose cores. When you split, as research shows us, you still can communicate with "talking persona" and "non-talking persona". So yes, effectively there are two "people", but they always been there. They just no longer coordinate well.
  • That the brain is approximately like jello in texture. That being said it also has some plasticity - it probably re-grew the connection to some level. It happens.
  • by ITRambo ( 1467509 ) on Tuesday October 03, 2017 @10:18AM (#55301345)
    While not as rapid nor efficient, the body's nervous system still connects the two halves of a split brain. It's a slower rural road type of path, that is not as efficient as the expressway connection that was cut. But, it exists and explains why the two halves still communicate, albeit less efficiently.
    • Exactly, the two sides are still communicating, though not as well. Think about it this way - if they weren't communicating it would be impossible for a person to do common activities like walking, since the each half controls a leg and without coordinating the legs couldn't move cooperatively and the person would just fall down. Likewise, driving would be a nightmare, and the list goes on.
    • by gweihir ( 88907 )

      Actually, it is a possible explanation only. More research is needed before an actual explanation can be found.

  • You are two ... (Score:5, Informative)

    by BenBoy ( 615230 ) on Tuesday October 03, 2017 @10:23AM (#55301385)
    CGP Grey did a nice, insightful piece on this in a 5 minute youtube piece [youtube.com] discussing just this thing. I like his videos in general ...
  • No wonder tech people are so neurotic -trying to think themselves into existence.

    A self, an individual, is an existing subject. A thought about something does not mean it exists.

    E.g. I can think about unicorns all day, but that doesn't mean unicorns exist.
  • by jenningsthecat ( 1525947 ) on Tuesday October 03, 2017 @11:00AM (#55301677)

    I lived across the street from a young girl - I'll call her 'Sandra' - who had grown into her mid-to-late teens when I moved away. She had been born without a corpus callosum, and her parents were warned that she would never be anything approaching normal, and might not even live.

    Apparently her parents did something right, or she herself possessed some kind of will or magic that got her beyond the difficulty. Other people who had kids born with the same lack would ask Sandra's parents for advice and support. Sandra was always a bit quirky, and when she was younger I always had the sense that she wasn't quite normal, even before I knew her history. But she was sweet and funny, she made pretty much normal progress in school, and she grew into a lovely young woman who didn't wasn't out of place among her peers in any significant way.

    So I'm not surprised at these new findings. The human brain seems to be very good at routing around damage in ways that we don't yet understand.

    • by Gr8Apes ( 679165 )
      I recall reading about some math genius that was born with hydro-encephaly and had something like less than 4% of his brain matter along an external ring along his skull. Genius level IQ. Granted, he's an exception, but it certainly puts into perspective how much we don't know about the brain.
    • Imagine being this guy, born without much brain at all, and yet not knowing it until much later in life:
      http://www.rifters.com/crawl/?... [rifters.com]

      The human brain is very good at doing the things a brain does, sometimes even when all of the parts we think are necessary are not there in the proper proportions or even there at all.

  • I remember seeing studies about this stuff when I was a kid.. Still creeps me out.

    • by Quirkz ( 1206400 )

      I think I saw recently that some of the Ghost Limb issues can be addressed by the ways the nerves were severed. I can't recall the source now, so I could be wrong, but I seem to recall that the effect could be cured by trimming or modifying the damaged nerve endings, and they would stop reporting phantom limbs.

      • I think I saw recently that some of the Ghost Limb issues can be addressed by the ways the nerves were severed. I can't recall the source now, so I could be wrong, but I seem to recall that the effect could be cured by trimming or modifying the damaged nerve endings, and they would stop reporting phantom limbs.

        Not Ghost Limb. Ghost Hand... They're different issues. Ghost Hans is also known as Alien Hand Syndrome. Its' where a limb, usually your hand and arm seemingly are acting of their own will and not of your conscious control. It's usually a condition that people who have had certain trauma or hemi sphere separation experience due to the splitting of the parts of the mind from being as connected as they were.

      • What happens with phantom limbs is twofold:

        First, the nervous system uses both positive ("there's something happening") and negative ("there's nothing happening") signals. If you amputate a limb, the brain stops receiving both types of signals, and the absence of negative signals is interpreted as sensations from the limb.

        Second, the boundaries between the parts of the brain controlling different parts of the body isn't sharp. If you cut off somebody's hand, signals from other areas such as the "arm" part

  • by karlandtanya ( 601084 ) on Tuesday October 03, 2017 @11:53AM (#55302083)

    FTH (and FTA):
    "Fortunately, all these separate parts are not autonomous agents. They are highly interconnected, all working in harmony to create one unique being: you."

    Almost none of that is true: You aren't unique. You aren't particularly highly interconnected. You aren't in self-harmony. You aren't a single "being". In fact, there are more bacterial cells in "you" human cells in "you"...and many peer-reviewed papers confirm that those bacteria do contribute to determining "your" behavior. And those autonomous agents inside of you? They are pretty darned autonomous.

    My freshman psych professor explained it to us this way: "There are a whole lot of different behaviors we can observe. Different parts of the organism have different jobs. One of those jobs is to make up stories. We call that one consciousness. The illusion that each healthy uninjured human body has one integrated consciousness is a complete fantasy. Injuries and other pathologies expose this fact in interesting ways, but fragmented and incomplete consciousness is the normal way of being for all of us."

    A good way to see the separation is to compare desire vs behavior. If there was one fully integrated and aware "consciousness", then desire and behavior would always be consistent. They're not. Not even close.
    Consider things we do even though we'd prefer not to: Habits, compulsions, and addictions. Tobacco smoking could be any of those. It's not hard to find a smoker who will tell you "I want to stop smoking".
    Or neurological phenomena, for example "the yips" (google it, it's a golf thing).
    On a more positive note, consider practiced skills--like touch-typing, playing musical instruments, batting a baseball, rollerblading, etc. You can't consciously decide "I will skillfully perform this act" and *poof* it's done.
    There's something in you that does (or does not) those things. But it's not the thing that's speaking to the person next to you.

    Lovecraft put it quite nicely:
    “The most merciful thing in the world, I think, is the inability of the human mind to correlate all its contents. We live on a placid island of ignorance in the midst of black seas of infinity, and it was not meant that we should voyage far.”

    • by Whibla ( 210729 )

      The illusion that each healthy uninjured human body has one integrated consciousness is a complete fantasy. Injuries and other pathologies expose this fact in interesting ways, but fragmented and incomplete consciousness is the normal way of being for all of us."

      A good way to see the separation is to compare desire vs behavior.

      This might be simply an artifact of the way my brain works but I'll put it out here and you can try it for yourselves...

      Perhaps a simpler way of seeing this separation is to do the following: Lie on one side for a few minutes, and let your mind find a train of thought. Follow that train for a little while. Now, roll over and lie on your other side. After you're comfortably settled ask yourself: Are your thoughts still on the same track?

      For me the answer is invariably "no". I suspect it has to do with blood

      • Where's the damn "like" button?

        Seriously though, I have no mod points, otherwise you would get some. Hacking your own meat is what I like to refer to at my "working definition of free will."

        Acknowledge you are not in control of most of the things you do. Your physical stuff has predilections and propensities that are, in most ways, hidden from your conscious thought. In fact, most of the "thinking" done in your head is non-verbal. You can't directly address those parts of your brain, but they sure can d

    • good thing your freshman psych professor knows everything or he could possibly have been wrong, and then you would be wrong as well.

      I always find it funny that we think we can understand the brain with the brain, how can something understand that which it is itself using to understand?

      all current progress has only gotten us to guessing, and we'll keep on guessing for a long time, i don't know if we can ever truly "know" how we work.

    • "But it's not the thing that's speaking to the person next to you."

      Well, maybe.

      I read a small number of books to my kids, with funny voices and everything, so many times that I could stop thinking about the process at all. My eye's scanned the words on the page, my voice made the noises, but I was off thinking about something else. The rest of my brain had pretty much automated the process.

      Sometimes my internal thought process would direct my eyes across the room to look at something, and I'd wonder why

  • by TheNarrator ( 200498 ) on Tuesday October 03, 2017 @12:29PM (#55302371)

    The guy with a tiny brain [newscientist.com] shows that we don't know a lot about the mind/body connection. That this guy was able to function as a normal human being is really astonishing.

    • "That this guy was able to function as a normal human being is really astonishing." It is amazing that Mr. Trump can tweet and chew gum at the same time.
    • Without getting all religious, there is some evidence to suggest that you (the entity that is self-aware) are not the brain.

      Generally speaking, doctors and medical scientists are firmly in the you=brain camp. One exception is cardiologists or ER physicians who've done a lot of defibrillation on heart attack victims. Do enough of them and you will get people who go through a near-death experience. Get enough people with NDE and sooner or later you will get a patient who describes seeing the operating room f

    • by zifn4b ( 1040588 )

      The guy with a tiny brain [newscientist.com] shows that we don't know a lot about the mind/body connection. That this guy was able to function as a normal human being is really astonishing.

      Wow... where is your evidence of this thing you refer to as "mind"? Please show peer reviewed cognitive science research the substantiates your claim. To my knowledge, there is no evidence of a "ghost in the machine". See: Daniel Dennett and Sam Harris for example.

  • by Khashishi ( 775369 ) on Tuesday October 03, 2017 @01:08PM (#55302707) Journal

    Most interesting questions are not defined precisely enough to have exact answers. The answer is fuzzy. In this example, the word "person" doesn't have a precise meaning, but just some vague context-sensitive meaning which we mostly agree on based on our shared upbringing. In some cases, some authority will make a more precise but arbitrary definition for the purposes of law. For example, legally blind. Legal person. So, if you split the brain, do you split the person? It depends on if some authoritative body declares it to be so.

  • Our brains are as large as they are so we can lie, cheat and persuade other humans and so we can throw things. If I want throw a rock and hit something it requires a degree of precision and coordination between my muscles that normally can't be done with nerve cells. The way our nerves work creates to much jitter. To solve this, we have orders of magnitude more nerves controlling our muscles than other mammals, so that the average transmission speed of signals in our nerves much more constant and predict
  • The corpus callosum is not the only connection between the halves of the cerebral cortex. There are all of the lower brain structures. And most modern callosotomies are incomplete. So no surprise that a modern researcher would get different results than the past.
  • This press release [wikipedia.org] from January the year. Same university. Not to say that it isn't interesting research, it is, but it is not news.

  • As far as I can say Cerebellum is never split ( https://en.wikipedia.org/wiki/... [wikipedia.org] ). When a brain is "split" they cut the Corpus callosum ( https://en.wikipedia.org/wiki/... [wikipedia.org]). The cerebellum may offer enought connections between the two emispheres
  • by istartedi ( 132515 ) on Tuesday October 03, 2017 @03:18PM (#55303643) Journal

    They split one brain structure, not the whole neurological system. I don't think they even split the whole brain, so it could be that lower level brain structures are picking up the slack. At the very least we know they didn't split the spine since that'd kill you. It's conceivable that these lower levels of the brain and peripheral nerves are an integral part of being a person. I've heard that the heart actually turns out to have more to do with personality than modern medicine once thought. It's not just a stupid pump. Users of artificial hearts report that it lacks that certain something. Receivers of transplanted organs sometimes acquire traits from the donor, such as food preferences. You wouldn't think such traits could be conferred via those organs. Your sense of self may be more "distributed" than some of us think.

  • After splitting the brain the person is dead.

"Only the hypocrite is really rotten to the core." -- Hannah Arendt.

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