Cognitive Daily

Here’s a fascinating video featuring split-brain researcher Michael Gazzaniga. The patient had his corpus callosum severed as a treatment for severe epilepsy. The treatment terminated nearly all communication between his brain’s right and left hemispheres.

Since language is primarily processed in the left hemisphere, the patient can’t name items on the left side of his field of vision (remember, the brain is “flipped” relative to the body parts it senses and controls). But he can draw pictures of them, and then he can look at the pictures and name them. (via Issues in the Philosophy of Cognitive Science and Mind)


  1. #1 Tommy
    October 4, 2007

    The split didn’t cause a split personality, I don’t know if that is logical or not.

    Does that mean our conscious is in both hemispheres?
    or that it communicates via another way?
    Or that 1 hemisphere is a slave of the other?

  2. #2 Anthony
    October 4, 2007

    Here is an even better video. Same man, Gazzaniga is in it, and it is hosted by Alan Alda. It is a segment from Scientific American Frontiers. The segment is titled, The Man with Two Brains (3rd from the top). I show this to my General Psychology class when we talk about the brain. They typically find it to be “pretty cool” and also confusing, until we discuss it.

  3. #3 Sven DiMilo
    October 4, 2007

    Thanks for posting this. i remember being fascinated by split-brain studies when I took psychology courses years ago, but seeing this was even more impressive than reading about it.

  4. #4 Tanasije Gjorgoski
    October 5, 2007

    Is just ability for speech located in the left hemisphere, or is it the general language capacity?
    I guess it can’t be general language capacity, as the right hemisphere in the video supposedly understands that what is needed to do is to draw what was seen?
    Has anyone tried to communicate separately with the right hemisphere?

  5. #5 Dave Munger
    October 7, 2007

    Split personality is completely different from split brain. Your right hemisphere doesn’t have a different personality from your left hemisphere.

    Here’s a pretty good summary of the effects of the corpus callosum surgery:

  6. #6 uk-baxter
    October 7, 2007

    reminds me of the guy getting shocked at the bigginning of ghost busters 1 by Dr. Peter that movie rocked

  7. #7 dr.
    October 7, 2007

    freudian slip?

  8. #8 galataranator
    October 7, 2007

    comment deleted — let’s keep it PG-13 and non-misogynistic, please.

  9. #9 lobster
    October 7, 2007

    As we can see, these expensive quacks, riding on their high horses, are again playing the god-trick, otherwise known as “learning as we plough along”, to arrive at nothing much. Like needlessly excising the tonsils, spleen, appendix, breasts and many more experiments to enhance their income whilst augmenting their stature, these put-on-a-serious-face jokers are nothing but ignorant butchers. Even worse are the so-called psychologists/psychiatrists and their shock and excise-when-in-doubt therapy which have literally driven many sane people fully insane and all because these state-of-the-art egotists deny their lack of realisation of simple absolutes. And what are the absolutes? You won’t want to know. Not when you’ve got the hope and faith that the pharmacological industry and those surgical magicians to look forward to. The body heals itself when we are a truly balanced personality, but not when we blame every little excuse for our ills. It all starts with the individual who is courageous enough to reject his guilt and anger, reject his own hypocrisy and start doing the right thing. Now. What? Reaching out for the cola and popcorn already or yelling for your team to win or cursing at ignorant idots who do not understand democracy, etc, etc. It’s ALL inside for when we do not have peace & satisfaction [or joy-in-progress] within, we have nothing without. Nothing but pain & problems because to react is asking to share others’ problems. And that will not be denied for the river do not care whether you know how to swim or not as you recklessly dives in to save some hapless drowning victim. To the physicians: heal thyselves first …. Because money & perceived stature is not everything, whether we like it, know it, or not.

  10. #10 anonna
    October 7, 2007

    lobster, you sound a bit angry. You might want to see someone about that.

  11. #11 izzy
    October 7, 2007

    Maybe lobster-girl/boy is SCIENTOLOGIST. I also think psych is overrated but that comment smacks of an agenda. Thanks I really hate flamers with their hidden premises.

  12. #12 coreyinprogress
    October 8, 2007

    This procedure is outdated, but was necessary to confine grand mal seizures to a single hemishere (thus not debilitating the entire brain) At the time severing the corpus collosum was the best way to do this. No real scientist is slicing and dicing just for fun.

    Anyway, i would have liked to have seen some of the effects besides the aphasia.

  13. #13 Viscount
    October 8, 2007

    lobster – I can see why you’d think this is a horrible thing to do, but you didn’t see what the epilepsy like prior to the surgery – it would have been absolutely debilitating. It took several decades, IIRC, for anyone to even notice behavioural or phenomenological differences in split brain patients, and they certainly report massive improvements in quality of life after surgery – frequency of seizures is reduced by something like 80-90%. After Sperry’s work that showed that there were some impairments, any patients who were candidates for callosotomy would certainly have been made aware of the side effects before consenting to the procedure.

  14. #14 Alex
    October 8, 2007

    The human brain-the final frontier.

  15. #15 Litamus
    October 8, 2007

    The doctor seems to be happy to finaly find a good material for his research on brain and mind.
    No body care about the man, especially if we notice that his illness was caused by a “sucessfull” surgical act!

  16. #16 stewart
    October 8, 2007

    I’ve seen a few ‘split-brain’ patients. Barring complications (always an issue) they’ve done pretty well. Remember, the ‘not being able to name things on the left’ is only for very brief presentations, otherwise they’ll just shift their eyes and name them. The most obvious finding in otherwise healthy folks is not being able to name objects placed in the left hand with eyes closed, but being able to use them accurately.
    Complications include strokes, and then you can end up with alien hand or apraxic syndromes, which can be quite challenging. However, for someone who’s had to wear a helmet for 5 years because of ongoing seizures, the drop in seizure frequency and necessary medications can help them get even a little life when none was possible before.

  17. #17 stewart
    October 8, 2007

    Dave, you may also want to think about those people who were born without the corpus callosum – agenisis of the corpus callosum is rare, but it’s not usually picked up except by accident, as it leaves few behavioral markers.

  18. #18 Dave Munger
    October 8, 2007

    the ‘not being able to name things on the left’ is only for very brief presentations, otherwise they’ll just shift their eyes and name them.

    Good point. Note that Gazzaniga has the patient focus on a dot in the center of the screen to avoid just this adaptation. Also, when he draws the picture, he has to shift his eyes so he sees it the right side of his field of vision.

  19. #19 Jake
    October 8, 2007

    I admit I am only a tourist in this field, having only taken Psych I in college, but does the effect of severing the corpus collosum impact “left brain/right brain” designation (lefties are right brained and righties are left brained) aside from aphasia, which is common in stroke patients- and what would it mean if you tested 50/50 right/left brained with an intact corpus collosum? And… are those psychological tests that identify right/left “brained-ness” even accurate diagnostic tools?

  20. #20 Despard
    October 8, 2007


    It’s not quite as simple as that. The left hemisphere always controls the right side of the body and vice versa. Language is almost always left-lateralised, and I’m not sure if handedness is always in the same hemisphere as language. So I’m not sure how much sense it makes to call people ‘left-brained’ or ‘right-brained’ in this way.

    I know that one way of finding out what each hemisphere does is to inject anaesthetic into one hemisphere at a time and then test the patient to see which impairments you find with each one. So in that case, it’s an accurate diagnostic tool but a bit of a drastic one!

  21. #21 Mom of an acc kid
    September 29, 2009

    I am a mother of a child with agenisis of the corpus callosum. I know quite a bit about her diagnosis and would be happy to answer questions you may have. And it does leave a lot of behaverial markers! Some are learning delays, Hyperactivity, Regression and autistic like tendancys. She is struggling with communication on a daily basis.

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