The Curious Case of Split-brain Patients

Author: Castin ,

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  • Castin
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    In severe cases of epilepsy, doctors have sometimes performed a surgery called a callosotomy. It severs the corpus callosum, the nerve bundle in the brain that allows the left hemisphere to communicate with the right. The idea was that if a seizure then occurred, it could not spread throughout the whole brain. The surgery has been quite effective in most cases.

    But what are the consequences of walking around with a split brain? A neuroscientist, who later won the Nobel Prize for his work, set out to investigate that question. The results of his case studies taught us a lot about hemispheric specialization, but also led him and other neuroscientists to arrive at a pretty audacious hypothesis: that the left and right hemispheres of a split-brain patient are independently conscious.

    ... indeed a conscious system in its own right, perceiving, thinking, remembering, reasoning, willing, and emoting, all at a characteristically human level, and ... both the left and the right hemisphere may be conscious simultaneously in different, even in mutually conflicting, mental experiences that run along in parallel
    — Roger Wolcott Sperry, 1974
    So the question: Are they separately conscious? Is that a reasonable theory to draw from Sperry's findings and the full case history?

    This will inevitably come down to what the definition of "consciousness" is. And there is no agreed upon definition of consciousness. Therein lies the difficulty. It's a question that isn't even sure what it's asking. A recent study declared split-brain patients have "divided perception but undivided consciousness". Yet where does perception end and consciousness begin? And how is the brain able to create a unified consciousness after it has been completely severed in two?

  • keithprosser
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    --> @Castin
    I wonder if a split-brain patient is half-way between a normal individual and conjoined twins.   it seems very much that each half of a brain can operate almost (but not quite) as well as an entire brain. 

    I don't think what happens in split-brain patient is any stranger or more mysterious than what happens in normal brains- but that is only because what happen in normal brains is so strange to begin with!
  • 3RU7AL
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    --> @Castin
    Some experiments show how each side of your brain specializes in certain types of information processing.

  • mustardness
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    Women have more bilateral brain action when asked series of questions in lab experiements.

    This is just one aspect of why woman is more complex than man.

    A more cosmic question is why bilateral?  Wouldnt four, 6 or 8 be more better, effective etc


  • keithprosser
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    --> @Castin
    Thinking on, I don't see split brains are more philosophically challenging than conjoined twins....  it's two brains in one body,although one supposes there is more unconscious communication in split brain situation...


  • Castin
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    As someone once asked:

    If a split-brain patient, disturbed that their right brain keeps acting with a will of its own, requests that their right brain be surgically removed, should that be considered therapeutic intervention or murder?
  • keithprosser
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    --> @Castin
    i think there would only be a probem if the right brain had enough independent self-hood to protest!   I'd use the conjoined twin model to get a handle on the issue.