"To reduce the severity of his seizures, Joe had the bridge between his left and right cerebral hemisphers (the corpus callosum) severed. As a result, his left and right brains no longer communicate through that pathway. Here's what happens as a result:"
While done in only the most severe cases of chronic seizures, the reasoning behind the split brain procedure is pretty solid. Seizures are caused by brain activity synchronizing over both hemispheres at extremely high levels. For a split brain patient, seizures will continue with little to no symptoms because when one happens on the left or right hemisphere, it will stay contained there. Patients have the fortune of living relatively normal lives after the procedure and only show abnormal behavior when they come up against a task where both sides can't be used at once. In fact, with this procedure it might be possible for a patient's left hemisphere to play a game of chess against the right and have an actual winner (spoiler alert: the left would probably win). Bad jokes aside, this condition gives insight into normal allocation of tasks to individual hemispheres. An example of this was shown in the Key-Ring Experiment.
"The left side of the brain contains all of the language centers. Therefore, whatever is in the left visual field (above: “RING”) can be spoken aloud. The right side of the brain is more abstract- relating to more “artistic” things- like spatial reasoning. Therefore, whatever can be seen in the right visual field (above: “KEY”) can be drawn or picked out, but it cannot be verbalized. This becomes extra cool when you ask the patient, “Why did you pick up the key?” In asking verbally, you are talking to the left side of their brain, which did not see the word KEY (They will say they only saw the word RING). Instead, they will come up with some logical reason (For instance, they might say something like “Oh, I was thinking about when I get to go home- I’ll need to grab my keys.” or “I liked the texture of the key.” or “I saw RING, and thought of my key ring.”). The reason depends on the person, but the mind can come up with a reasonable explanation (albeit inaccurate) for any behavior. Split brain research helped us to realize that this sort of reasoning happens in the left hemisphere. " --http://neurolove.tumblr.com
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