Saturday, August 13, 2022

What Is A Split Brain Patient

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Yes Split Brains Are Weird But Not The Way You Think

Split-Brain Patients
Michael Egnor

University of Chicago evolutionary biologist Jerry Coyne concludes from studies of post-operative epilepsy patients whose brains have been split that will, volition and consciousness are the results of purely physical processes in the brain perhaps the notion of consciousness and of will are things that merely report to us after the fact the deterministic actions of our brain, and are not in any way part of a causal chain. He writes:

The interesting bit to me is how this division of the brain seems to divide consciousness or awareness as well as volition. This is based on some stuff we already knew: for example, that visual information from the left eye goes to the right side of the brain and vice versa, and also that the language center resides on the left side of the brain.

So heres one experiment about consciousness. You present the word key to the subjects left eye only. That visual information goes to the right side of the split brain. When you ask the subject what word she saw, she says I saw nothing, because the ability to formulate language is on the other side of the brain, the left side. This apparently means that the consciousness of having seen the word has been split.

Jerry Coyne, The weirdness of split-brain experiments at Why Evolution Is True

Not so fast. Like most commentators on this important research, Coyne misunderstands its implications.

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Clayout For Operation Sterile Technique

Split-brain surgery requires steady hands which is facilitated by working in a seated position at a low table with suitable blocks or shelves on which to rest the wrists . Instruments may be laid out on a higher wooden shelf over the subject. These shelves are covered in sterile drapes which form a tent over the subject to which an assistant may gain access from the side opposite the surgeon for administration of injections, etc.

FIG. 2. Surgical layout for commissurotomy, baboon. Removal of bone cap. High-speed drill, bottle of sterile saline and suction cannulae made from hypodermic needles.

The subject is oriented so that the head is supported either transversely with respect to the surgeon, or with the nose aimed towards him. For accurate control of the direction of deep midline penetration it is important to verify that the sagittal plane of the subject is as near vertical as possible and directly in front of or directly below the surgeon’s eyes.

Michael C. Corballis, in, 2019

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Role Of The Corpus Callosum

The corpus callosum is a structure in the brain along the longitudinal fissure that facilitates much of the communication between the two hemispheres. This structure is composed of white matter: millions of axons that have their dendrites and terminal boutons projecting in both the right and left hemisphere. However, there is evidence that the corpus callosum may also have some inhibitory functions. Post-mortem research on human and monkey brains shows that the corpus callosum is functionally organised. It proves that the right hemisphere is superior for detecting faces. This organisation results in modality-specific regions of the corpus callosum that are responsible for the transfer of different types of information. Research has revealed that the anterior midbody transfers motor information, the posterior midbody transfers somatosensory information, the isthmus transfers auditory information and the splenium transfers visual information. Although much of the interhemispheric transfer occurs at the corpus callosum, there are trace amounts of transfer via subcortical pathways.

When You Split The Brain Do You Split The Person

My Psychology Blog: Sperry and Gazzaniga: The Split Brain Study

When you split the brain, you still end up with only one person. However, this person experiences two streams of visual information, one for each visual field. And that person is unable to integrate the two streams. It is as if he watches an out-of-sync movie, but not with the audio and video out of sync.

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The Behaviour Of Split Brain Patients

Paper Type: Free Essay

Split-brain patient is a denomination used for people who had the corpus callosum severed by surgery to minimise the seizures of a medicine intractable and multifocal epilepsy , commissurotomy is the name of this operation and it is a very rare technique and some patients only had partial split . The corpus callosum is a Latin word means thickened skin, described by Galen in the second century it is the largest white bundle of axons in the human brain that communicates the two hemispheres, the term commissures was introduced by Felix Vicq dAzyr to indicate the fibre pathways as he understood that the corpus callosum was constituted of nerves. The American Walter Dandy who cut the corpus callosum in the 1930 to have better access to brain tumours led to a new start on an investigation of the corpus callosum as the patients did not show any mental, motor or intellectual anomalies. However, most of the split-brain case studies were performed by Joseph Bogen in the 1960s.

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The major discoveries of the split-brain patients were the lateralisation of function, cross-cueing and the concept of the interpreter leading to the theory of a modularized brain.

Viicorpus Callosum And Consciousness

The study of split-brain patients during the past 40 years has helped change our understanding of the nature of consciousness. It has offered a prime example of the modularization of cognitive processes and documented the distinctions between a dominant and nondominant hemisphere. It has raised the question of whether the callosum may have played a unique role in the development of human consciousness. One of the key observations made regarding the Vogel and Bogen series of commissurotomies was that severing the callosum seemed to yield two separate conscious entities with the ability to respond independently. The idea of a dual consciousness was embraced by some scientists such as Pucetti, who hypothesized that the human condition was always made up of dual-consciousnesses that were only revealed after the section of the callosum. Others rejected the status of the right hemisphere as conscious. Daniel Dennett concluded that the right hemisphere had, at best, a rudimentary self.

Eran Zaidel, in, 1998

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Why Do I Have A Split

He found that if hemispheres were not connected, they functioned independently of one another, which he called a split-brain. The split-brain enabled animals to memorize double the information. Later, Sperry tested the same idea in humans with their corpus callosum severed as treatment for epilepsy, a seizure disorder.

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Split-brain patient ‘Joe’ being tested with stimuli presented in different visual fields

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Other Aspects Of Cognition

Split-brain studies have also contributed to the exploration of hemispheric specialization for other aspects of cognition. For instance, a few studies have shown that the left hemisphere is usually more efficient at performing mathematical operations than the right hemisphere, even though both are able to compare numerical representations. There are also evidences that the isolated right hemisphere is superior at making temporal judgments, such as making fine temporal discrimination, which contrast with divided visual field studies of neurologically normal adults suggesting a left-hemisphere advantage. On the other hand, split-brain studies have also helped us understand the contribution of subcortical structures and different portions of the CC. For instance, subcortical structures are able to transfer some information to both isolated hemispheres, such as contextual information and a few aspects of spatial localization.

Charles Watson, … George Paxinos, in, 2010

Disadvantages Of Having A Split Brain

As you might imagine there are more disadvantages than advantages of having a split brain. When the right and left side of the brain are un able to communicate then it can cause an almost split personality and actions performed by either hemisphere can be performed without the other hemisphere being aware of it.

An example of this being shown is in the most famous split brain study of all time Sperry, 1968. In this study each participant, who had had their corpus callosum removed, was shown the same picture in each eye and when shown in the second visual field they had no recollection of having seen it already.

Another interesting thing that was done was they were shown two different images, one in each visual field and when asked to draw the image they had just seen they would draw the image they saw on the left but they would then describe it as the image they saw on the right. This shows that the left side of the brain, which controls the right visual field, contains the information to be able to describe an object when seen visually.

This is the same when dealing with things in a tactile way. Participants were given objects to touch and then say their name or describe them and they could only do this with things in their right hand. They were however able to pick out objects using both hands that they were asked to and they were able to perform this task simultaniously which a normal person would have great difficulty doing.

About Alexander Burgemeester

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Roger Sperrys Split Brain Experiments

In the 1950s and 1960s, Roger Sperry performed experiments on cats, monkeys, and humans to study functional differences between the two hemispheres of the brain in the United States. To do so he studied the corpus callosum, which is a large bundle of neurons that connects the two hemispheres of the brain. Sperry severed the corpus callosum in cats and monkeys to study the function of each side of the brain. He found that if hemispheres were not connected, they functioned independently of one another, which he called a split-brain. The split-brain enabled animals to memorize double the information. Later, Sperry tested the same idea in humans with their corpus callosum severed as treatment for epilepsy, a seizure disorder. He found that the hemispheres in human brains had different functions. The left hemisphere interpreted language but not the right. Sperry shared the Nobel Prize in Physiology or Medicine in 1981for his split-brain research.

In the 1960s when Sperry conducted his split-brain research on humans, multiple scientists were studying brain lateralization, the idea that one hemisphere of the brain is better at performing some functions than the other hemisphere. However, researchers did not know which tasks each side of the brain was responsible for, or if each hemisphere acted independently from the other.

Advantages Of Having A Split Brain

SOLVED:A split

Often this operation is seen as a bad thing and it does have both positive and negative effects but on thing that you can do better after the operation is performing two tasks at once. A study performed by Rogers et al, 2004 found that when you have two halves of a brain then it increases your ability to both look for food and watch for predators at the same time. Purhaps indicating that the connections between our ancestors brain hemispheres were less developed.

In some rare cases when you have a developed language centre on both the left and right side of the brain then you are able to read two pages of a book at the same time and retain both sets of information. This was found in the case of Kim Peek who as well as a lack of corpus callosum also possessed the ability to speed read and memorise books verbatim.

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The Classic View Of The Split Brain Has Been Challenged

    In Nobel Prize research beginning in the 1960s, Roger W. Sperry and colleagues studied the effects of cutting the forebrain commissures in patients as a radical treatment for intractable epilepsy. Splitting the brain, they concluded, divided consciousness itself, and showed the two sides of the brain to have mental capacities that were in some ways complementary. The left brain was said to be linear, verbal, and logical the right brain diffuse, nonverbal, emotional, intuitive and creative.

    This work has had a profound influence on contemporary culture in diverse areas, including art, education, literature, medicine and even business. So-called right-brain thinking has even come to be seen as a corrective to the left-brain bias in the Western education systems. More emphasis on the right brain, it is suggested, should enhance empathy and creativity.

    Recently, though, an article by the Dutch neuropsychologist Yair Pinto and colleagues in the prestigious journal Brain has challenged the view that consciousness is divided into the split brain. Consciousness, they suggest, is in fact integrated into the split brain, but visual perception is divided. But this, in turn, was rebutted by Lukas J. Volz and Michael S. Gazzaniga, who had worked closely with Sperry in the early work.


    Pinto, Y., Neville, D.A., Otten, M., Corballis, P.M., Lamme, V.A.F. … Fabri, M. . Split brain: divided perception but undivided consciousness. Brain . doi:10.1093/brain/aww358.

    Split Brain Patients What Happens When You Have Two Brains

    Despite what you might have thought this does not happen when someone has a splitting headache but is usually the result of a surgery to treat refractory epilepsy. This usually involves cutting through the middle of the brain, known as the corpus callosum, and separating the two halves of the hemispheres effectively leaving the patient with two brains.

    Once this operation has been performed we see some remarkable changes to how you can perceive things and some of the results can show you how much we rely on the connection between the two halves of our brain.

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    What Happens When The Two Minds Are At Odds

    When the two minds of a split brain are at odds, the left hemisphere tries to rationalize what it doesnt understand. The right hemisphere often acts on autopilot. This phenomenon demonstrates that the unconscious mind can control our behavior. What hemisphere do deaf people use to process sign language?.

    What Did Michael Gazzaniga Discover In His Split Brain Research

    Split brain with one half atheist and one half theist

    4.6/5his studiessplitbrainGazzaniga discoveredbrain

    Consequently, what did Roger Sperry and Michael Gazzaniga discover?

    In the early 1960s, Sperry and colleagues, including Michael Gazzaniga, conducted extensive experiments on an epileptic patient who had had his corpus collosum, the “bridge” between the left and right hemispheres of the brain, split so that the connection was severed. Sperry received the Nobel prize in 1981.

    Beside above, what was the experimental method in Gazzaniga Split Brain Experiment?In 1962, after W.J.’s operation, Gazzaniga ran an experiment in which he asked W.J. to press a button whenever he saw an image. Researchers would then flash images of letters, light bursts and other stimuli to his left or right field of view.

    Similarly, it is asked, what is Michael Gazzaniga best known for?

    Dr. Gazzaniga, 71, now a professor of psychology at the University of California, Santa Barbara, is best known for a dazzling series of studies that revealed the brain’s split personality, the division of labor between its left and right hemispheres.

    What is Michael Gazzaniga associated with?

    Michael S. Gazzaniga is a professor of psychology at the University of California, Santa Barbara, where he heads the new SAGE Center for the Study of the Mind. He is one of the leading researchers in cognitive neuroscience, the study of the neural basis of mind.

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    Two Brains In One Head: The Story Of The Split

    Are you left-brained or right-brained? Are you the hard-working, problem-solving, number-loving, office dweller? Or the creative, passionate, playful, day-dreaming artist? These images often made me rather livid as a science-inclined child because obviously I wanted to identify with the half of the brain spewing swirls of bright colors rather than the one depicting darkened cubicles or esoteric math equations. The artists creating these polarizing images were just trying to boost their own egos and frame the rest of us as boring, right? Did becoming a scientist really entail accepting that the core of my being was equation-ridden and tragically colorless?

    Thankfully, no. The idea that a person is right-brained or left-brained is a myth, perhaps only slightly less ridiculous than the widespread belief that humans only use 10% of their brains.

    However, the brain is indeed split into a right and left hemisphere, and the two are connected by a structure called the corpus callosum, a bundle of nerves through which information can be shared. Imagine two incredibly powerful computers connected by a bundle of wires such that each computer has access to the data that the other one is processing. How would you determine which computer was processing what? You guessed it. Cut the cords.

    Check out a real split-brain patient doing a variation of this task!


  • Gazzaniga, MS. The split brain in man.Scientific American . at < >
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