Mind Naturalism

Are split-brain people really two half-persons? No, and that deepens the “mystery of consciousness”

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From cognitive psychologist and physicist Yaïr Pinto at Aeon:

We’ve got to admit that split-brain patients feel and behave normally. If a split-brain patient walks into the room, you would not notice anything unusual. And they themselves claim to be completely unchanged, other than being rid of terrible epileptic seizures. If the person was really split, this wouldn’t be true.

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. When stimuli appeared in the left visual field, they virtually never said (or indicated with the right hand) that they saw nothing. Rather, they would accurately indicate that something had appeared, and where.

And there’s more. While the previous model provided strong evidence for materialism (split the brain, split the person), the current understanding seems to only deepen the mystery of consciousness.More.

Actually, it doesn’t deepen the mystery of consciousness so much as it gives us a sense of its depth, a depth well beyond elegant essays introducing the latest speculation.

See also: Human self-awareness without cerebral cortex

and

Post-modern science: The illusion of consciousness sees through itself

5 Replies to “Are split-brain people really two half-persons? No, and that deepens the “mystery of consciousness”

  1. 1
    polistra says:

    Sounds like a difference of degree, not an absolute difference.

    Pinto et al did more asking and probing than Sperry et al, and got a better map of the true boundaries.

    Probably something like ‘lazy eye’, where the brain gets accustomed to ignoring the unfocused or blurred bad eye but can immediately use it when necessary. In this case the easier connection of conscious left and conscious right through the corpus callosum is gone, but somewhat longer paths through decussations in the brainstem are still there.

  2. 2
    Origenes says:

    Important article. Thanks news!
    Take home message is that Sperry and Gazzaniga were wrong — there are no two half-brain patients.

    Yaïr Pinto: We’ve got to admit that split-brain patients feel and behave normally …

    “Got to admit”? Whence the reluctance? Shouldn’t a scientist be neutral on these matters?

  3. 3
    J-Mac says:

    Consciousness is no mystery in case of the split-brain or the great majority of the brain missing, like in case Dr. Egnor described in his article at EN:

    ” I have scores of patients who are missing large areas of their brains, yet who have quite good minds. I have a patient born with two-thirds of her brain absent. She’s a normal junior high kid who loves to play soccer. Another patient, missing a similar amount of brain tissue, is an accomplished musician with a master’s degree in English.

    https://uncommondescent.com/mind/are-split-brain-people-really-two-half-persons-no-and-that-deepens-the-mystery-of-consciousness/

    Why not a mystery? Well, if we consider that consciousness is quantum and parts of neurons called microtubules communicate via quantum entanglement, in theory even a small part of the brain can generate conscious experience… though other brain functions could be affected…

  4. 4
    EricMH says:

    If there is still a physical communication path between the halves, why do split brain patients present a problem for materialism?

    I would understand if the remaining path is inadequate for the sort of communication necessary between the halves, in which case the normalcy of split brain patients would be evidence for some sort of immaterial unity.

    Is this the underlying issue, that the existing path does not seem adequate for communication between the halves?

  5. 5
    Axel says:

    Atheism, as the primordial assumption for the scientific paradigm, keeps proving to be hilariously out of date.

    It puts me in mind of the ‘bon mot’, not all together unallied, of St John Vianney, to the effect that the male sexual urge did not cease until ten minutes after rigor mortis has set in.

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