LMSS SPHINCTER vol.80 iss.2 Winter Issue - Page 14


S plitting B rain &



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 !!
Article by :
Harry Bickerstaffe
2nd year medical student
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 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
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 patient 2 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 .
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 .
Back to cutting your brain in half !
The diagram above 3 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
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 .
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 in the slides , the patient was asked what she saw , she said “ nothing ”, but then started to laugh . When asked what was funny she told the researcher she didn ’ t know , saying that maybe it was something to do with the machine . 4
What would happen to your sense of “ self ” the moment your brain is split ?
The apparent liberation of the right brain can be seen when split brain patients draw two different figures at the same time , a task 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 .
The most startling realisation is that we have every reason to believe the right hemisphere is conscious . In fact it is easier to establish the consciousness of the isolated right hemisphere than most toddlers . In even more dramatic operations patients have had their left hemisphere removed , leaving only their right — we rightly think of them as conscious . Patients with only a right hemisphere can live fruitful lives . 6 How then could the presence of a separate left hemisphere rob the other side of its consciousness ?
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 .
Sphincter magazine | volume 80 issue 2 | Winter 2016 edition
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