LMSS SPHINCTER vol.80 iss.2 Winter Issue - Page 8

8 S plitting C Article by: Harry Bickerstaffe 2nd year medical student B rain & The onsciousness 9 Editor’s Note: Harry knocks it out of the park again, with an enthralling article, on the interesting concept of consciousness, relating to evidence and cases of corpus collosotomy, and how this affects a person. Amazing stuff Harry, thank you!! The split brain phenomenon drives us to wonder whether an area that has no effect on “my” consciousness is in fact an area that houses a different consciousness Splitting the Brain & Consciousness Sphincter 80:2 December 2016 You are going to the doctor to have your brain cut in half. You probably have epilepsy, very bad epilepsy because you’re saying goodbye to the 200 million axons of your corpus callosum as a last resort. The easiest experiments with split brain patients exploit the fact that visual fields are interpreted by the opposite brain hemisphere — remember that nearly all body muscles are controlled by the opposite side of the brain (things get confusing very quickly if we forget that). Showing an image to the right eye means only the left hemisphere will see it, in a split brain patient. Reference 3. Cleverly the word appears for less time than it takes for saccadic eye movement, ensuring only one hemisphere will see the word. In this experiment images are used, words have also been used as understanding individual words is not confined to one hemisphere. by right hemisphere) will pick up the hammer. To make this trickier the objects are hidden behind a screen. The patient chooses the right object from amongst 20 others. When asked what object they are holding behind the screen the patient’s talkative left hemisphere cannot say. When the object is brought out from behind the screen and the patient is again asked why she chose this object out of 20 possibilities the answer is confabulated, or simply not known. This is peculiar. Back to cutting your brain in half! The diagram above3 shows a classic experiment: the written explanation is a bit wordy, but worth it. A split brain patient again sees words flash infront of her. Each word is only seen by one side of the brain. Every word is an object. When the left eye, i.e. the right hemisphere, sees the word “hammer” and the patient is asked what she sees, she says “nothing”, as the left hemisphere (responsible for speech) really does see nothing. However, when asked to pick up the object that they didn’t see the word for, the left hand (controlled Back to cutting your brain in half. There are no pain receptors in the brain and hemispherectomies have been performed without loss of consciousness, so we can cut you when you’re awake, too. What would happen to your sense of “self” the moment your brain is split? Does your subjectivity collapse into a single hemisphere, or do you disappear and become replaced by two new consciousnesses? You cannot be on both sides of the great divide. to each eye only went to one hemisphere), it was discovered that only simple learning acquired through one eye could transfer to the other hemisphere. Given the vast amount of data in each hemisphere of human brains, it seems likely that a normal brain will be functionally split in some ways. Two hundred million nerve fibres seem insufficient to integrate the simultaneous activity of some 20 billion neurons in the cerebral cortex, each of which makes thousands of connections. It is perhaps tempting to think that “you” will always fall into the left hemisphere, that you will be the one that converses with your loved ones, and the researchers. Yet who will shake their hand with your left hand, recognise their facial expressions and tone of voice? The straightforward answer is that consciousness is divisible. Just as two different brains do not share consciousness, the consciousness of a single brain does not need to be shared when the connections are cut. And if there were to be a way of linking two brains with an artificial corpus callosum, we should expect that what had been two distinct persons would be unified in the only sense that consciousness is ever unified, as a single point of view, and unified in the only sense that minds are ever unified, by virtue of common contents and functional abilities.7 The idea that you may not be the only consciousness point of view reading this text is flabbergasting. I cannot even feign knowing enough to guide us on a journey down the rabbit hole that is the theories of consciousness. Nevertheless, I want to highlight a few unusual points. “The simple truth is that your mind can be split with a surgeon’s knife.” Now some astonishing and subtle things are going to happen - as your brain and mind are split. Firstly, your epilepsy will hopefully have improved. Apart from that, you appear to have remarkable ‘social ordinariness’ — how disappointing for the researchers hoping to probe you.1 However, when then asking one young split brain patient2 what he wanted to be when he grew up: his left brain - where language control lies for most people - verbally responded “a draftsman” whereas his right brain used his left hand to write out “racing driver”. Maybe not so normal after all. WRITE FOR SPHINCTER NOW!!!! ISSUE 3, COMING OUT FEBRUARY 2017 impossible for normal people. In the acute phase after surgery the patients’ left and right hands can be seen engaging in a tug of war over an object or even sabotaging each other’ s work! The left hemisphere (with which you would converse) can explain their operation and their condition, yet the left hemisphere remains naive as to the experiences of the right hemisphere. Years after surgery the left hemisphere may still express frustration when the right hemisphere responds to researcher’s instructions.5 To ask the left hemisphere what it is like not to know what the right hemisphere is thinking is rather like asking a normal person what it is like not to know what another person is thinking. In a different experiment a split brain patient watched a series of picture slides, only seen in the left visual field, so the right hemisphere. At one point a nude photo appeared The most startling What would in the slides, realisation is that we have the patient was happen to your every reason to believe asked what she the right hemisphere is sense of “self” conscious. In fact it is saw, she said the moment your easier to establish the “nothing”, but then started to consciousness of the brain is split? laugh. When isolated right hemisphere asked what than most toddlers. In was funny she even more dramatic told the researcher she didn’t operations patients have had their know, saying that maybe it left hemisphere removed, leaving was something to do with the only their right — we rightly think machine.4 of them as conscious. Patients with only a right hemisphere can The apparent liberation of the live fruitful lives.6 How then could right brain can be seen when split the presence of a separate left brain patients draw two different hemisphere rob the other side of figures at the same time, a task its consciousness? Sphincter magazine | volume 80 issue 2 | Winter 2016 edition Back to cutting your brain in half. There are no pain receptors in the brain and hemispherectomies have been performed without loss of consciousness, so we can cut you when you’re awake, too. What would happen to your sense of “self” the moment your brain is split? Does your subjectivity collapse into a single hemisphere, or do you disappear and become replaced by two new consciousnesses? You cannot be on both sides of the great divide. You let me cut your brain in half, so now you can electrocute mine a bit. You expose my cortex and stimulate various parts with a microelectrode to see what effects each part has on my consciousness. What could either of us make of an area that, when stimulated has no effect on “my” consciousness? I may say nothing happened. The split brain phenomenon drives us to wonder whether an area that has no effect on “my” consciousness is in fact an area that houses a different consciousness (possibly among many different consciousnesses in my brain)— like the right hemisphere being unknown to the articulate left, in split brain patients. Here lies a perhaps insurmountable challenge in studying consciousness. As long as we must correlate first person changes with changes in the brain we may fail to take into account the aspects of consciousness which are not functionally articulate, yet may be conscious. The uncanny point about consciousness can be made far more eloquently by neuroscientist and philosopher, Sam Harris, “there is nothing about the brain, studied at any scale, that even suggests that it might harbor consciousness — apart from the fact the we experience consciousness directly and have correlated many of its contents, or lack thereof, with processes in our brains.”7 As for unconscious thinking, I have completely ignored it in this article — in an effort to reduce the number of embarrassing mistakes. However, studying the boundary between conscious and unconscious thinking has been Thank you to: The simple truth is that your mind can be split with a surgeon’s knife. What if my brain is not cut in half? Roger Sperry won the 1981 Nobel Prize for his work with split brain patients on brain function asymmetry, which was briefly alluded to above. However some of his work in the 1950s demonstrated that our brains may already be split to some degree. After cutting the optic chiasma in cats (so that inputs For Stocking: Pick Yours up for FREE now!!!! getting increasingly precise and a good place to look may be Daniel Kahneman’s Nobel Prize winning theories of two systems in making decisions.8 Another eery area is the disorder of “blind sight”, where you think you are completely blind — yet when asked to guess what is in front of you, you can give a near perfect description.9 The one fact we can (try to) rejoice in is that even ridiculous-sounding procedures can lead to remarkable discoveries. Notes: 1. Bayne, T. 2008. “The Unity of Consciousness and the Split-Brain Syndrome”, The Journal of Philosophy, 105(6), 277-300. 2. This patient was slightly strange as he expressed language ability in both hemispheres. 3. Wolman, D. 2012. “The Split Brain: A Tale of Two Halves”, Nature 483, 260–263. Diagram adapted, using https://neuwritesd. org/2015/08/27/two-brains-in-onehead-the-story-of-the-split-brainphenomenon/ to depict a slightly stranger experiment. 4. Page 704-710 of F. M. Bear’s “Neuroscience: Exploring the Brain”, International Edition, 4th edition 5. Gazzaniga, M. S., Bogen, J. E., & Sperry, R. W. (1962). “some functional effects of sectioning the cerebral commissures in man”, Proceedings of the National Academy of Sciences of the United States of America, 48(10), 1765–1769. 6. Hemispherectomy patients’ intelligence often goes up, likely since their other hemisphere is causing less seizure problems. In a similar example, Locked-In Syndrome can render a person devoid of the complex behaviours we correlate with consciousness. Jean-Dominique Bauby had Locked-In Syndrome and could only communicate via blinking his left eyelid, but no one would doubt his consciousness — especially when reading his haunting recount of his experiences in his new body and in hospital (“The Diving Bell and The Butterfly”, 1997). 7. Chapter 2: The Mystery of Consciousness of Sam Harris’s “Waking Up”, 2014 8. Daniel Kahneman’s “Thinking, Fast and Slow”, 2012 9. Weiskrantz, L. (2009), ‘Is blindsight just degraded normal vision?’, Experimental Brain Research 192(3), 413--416. Sphincter magazine | volume 80 issue 2 | Winter 2016 edition