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When You Split the Brain, Do You Split the Person? (aeon.co)
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.
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.
Earlier experiments used a partition to separate the left and right visual fields. One experiment I recall reading about was done like this: On one side of the partition they would place an implement, such as a fork. They would then have the subject pick up the implement in one hand and ask them to identify it, and do various things with it. The results were markedly different depending on which side of the partition, and therefore which eye and which hand, were engaged.
Here is some general information on the early experiments.
I've fallen off your lawn, and I can't get up.
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.
CGP Grey did a nice, insightful piece on this in a 5 minute youtube piece discussing just this thing. I like his videos in general ...
Anybody over 6'1" would be called 'Big Jim", anybody under 5'7" would be called "little Jimmy"
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.
'The Economy' is a giant Ponzi scheme whose most pitiable suckers are the youngest among us and the yet-unborn.
The corpus callosum isn't the only connection between the left and right half of the brain.
The architecture of the human brain is a bit like an onion; at the core is the basal ganlia -- also popularly known as the "reptilian brain". Outside/above that is the limbic system, called the "paleomammalian complex" in the triune brain theory. Above that is the neocortex, the part we tend to indentify ourselves with because it does all the cool stuff that more primitive organisms can't, like language.
The corpus callosum sits roughly in the middle of the limbic system -- the middle of the middle if you will. Just above it is the cingulate gyrus, responsible for processing emotions, learning, linking behavior to goals. The cingulate gyrus is the anatomicaly lowest part of the brain that doesn't have its own connections between hemispheres. I find that fascinating and suggestive. Immediately below the corpus callosum is the septum pellucidum, which is a thin, midline structure. Every part of the brain below the septum pellucidum is richly connected across sides.
This situation is like a company run by partners. The partners don't talk to each other, but they share subordinates, including a secretary who keeps them up to date on what each other is doing. The secretary quits, and the company is at least temporarily less coordinated, but the other subordinates still talk to each other and over time may take up some of the communication burden.
One of the big difference in brain science today from when I studied it thirty years ago is that we know the brain is much more plastic than we ever imagined. There have been well-documented cases of people with brain injuries doing things they taught me was impossible back then, like people who lost an entire brain hemisphere regaining some motor control on the affected side. The only way this would be physically possible is for the remaining hemisphere to radically remodel itself.
Anyhow cross visual field object awareness is a good candidate for function restoration, because the nerves from the eyes enter the brain well below the level of the corpus callosum; there are no direct connections from the optic nerves to the cortex. How that awareness comes about/is restored is an open question. It could be that the cortexes develop other way of communicating, or it could be that the hemisphere you're talking to develops awareness of stuff that would normally be processed by the other side.
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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.”
"Reality is that which, when you stop believing in it, doesn't go away." - Philip K. Dick
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.
For all intensive purposes, "whom" is no longer a word. That begs the question, "who cares"?