It is worth noting that in the 50s, neuroscientists were still not ...
(Middle Column annotation)
Nowadays, procedures that involve cutti...
I had understood that sensory input was given to the each hemispher...
In this experiment cats were trained to navigate a maze while weari...
Sperry would go on to win the 1981 Nobel Prize in Physiology or Med...
In [this video](https://youtu.be/lfGwsAdS9Dc?t=143) you can see a s...
If you are interested in learning more about the experiments Roger ...
Interesting, why wouldn't the patient just ask, "Was anything shown...
More [recent studies](https://www.ncbi.nlm.nih.gov/pubmed/9572734) ...
As confirmed by recent studies, the left hemisphere’s dominance for...
*Laurence Kim Peek* was an American savant that was born with agene...
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© 1967 SCIENTIFIC AMERICAN, INC
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© 1967 SCIENTIFIC AMERICAN, INC
© 1967 SCIENTIFIC AMERICAN, INC
© 1967 SCIENTIFIC AMERICAN, INC
As confirmed by recent studies, the left hemisphere’s dominance for language is complemented by the right hemisphere’s dominance for visuospatial processing. Several studies have shown a right hemisphere superiority for tasks involving [spacial relationships](https://www.sciencedirect.com/science/article/pii/0028393273900390), [apparent motion detection](https://www.ncbi.nlm.nih.gov/pubmed/10683394) and [mirror image discrimination](https://www.ncbi.nlm.nih.gov/pubmed/10509836).
Sperry would go on to win the 1981 Nobel Prize in Physiology or Medicine for his discoveries concerning the functional specialization of the cerebral hemispheres.
In this experiment cats were trained to navigate a maze while wearing an eye patch. As expected, after a while, the “split-brain” cats learned their way around the maze. However, when the eye patch was switched to the other eye, the cat started getting lost in the maze again. The same was not observed in cats that had not had their corpus callosum severed.
In [this video](https://youtu.be/lfGwsAdS9Dc?t=143) you can see a similar experiment being performed with a real patient.
More [recent studies](https://www.ncbi.nlm.nih.gov/pubmed/9572734) have highlighted how much hemisphere abilities can differ from patient to patient. In one example, a split brain patient was able to generate speech from her left hemisphere but not from her right, and, conversely was able to generate written language from her right hemisphere but not her left. For a long time it was thought that spoken and written language relied on similar cognitive mechanisms and would therefore be controlled by the same hemisphere.
I had understood that sensory input was given to the each hemisphere from the opposite side of the body, i.e. the left hemisphere receives information from the right eye and vice-versa (except for the nose as the right nostril is connected to the right hemisphere and vice-versa).
In this case I would expect that the right eye dispatches information to the left brain.
Interesting, why wouldn't the patient just ask, "Was anything shown on the screen?"
*Laurence Kim Peek* was an American savant that was born with agenesis of the corpus callosum (i.e. complete or partial absence of the corpus callosum).
Among other things, Peek was able able to read books extremely fast and was able to remember almost everything he had read. It was reported that he could accurately recall the contents of 12,000 books. Peek read by scanning the left page with his left eye and the right page with his right eye. According to his dad he could read a page of a book in about 10 seconds. If you are interested in learning more about Kim Peek, [here is a documentary about him](https://www.youtube.com/watch?v=DLpCfHH1OVU).
(Middle Column annotation)
Nowadays, procedures that involve cutting the corpus callosum to reduce epileptic seizures are still used in special cases. That said, for the context of this paper, one should remember that procedures like lobotomies were still commonly employed throughout the 1950s.
It is worth noting that in the 50s, neuroscientists were still not completely sure about the role of the *corpus callosum* in the human brain. A lot of scientists at the time suspected that it played a role interhemispheric communication. But nobody was actually sure. There were multiple known instances of functioning human beings that had been born without a corpus callosum (revealed via X-rays). This is actually known as **Agenesis of the corpus callosum** which is a rare congenital disorder but at the same time one of the most common brain malformations observed in human beings.
You are mostly right. In a normal brain, the optical sensory input coming from an eye is delivered, *for the most part* to the hemisphere in the opposite side of the body (left eye to right hemisphere and vice-versa). However, there is also ipsilateral optic nerve communication (left eye to left hemisphere) because there is a optic nerve connection between the left eye and the left hemisphere (and the same is true for the right side).
In this case, in addition to having the connection between the two brain hemispheres severed the cat had its *optic chiasm* (the X-shaped structure formed at the point below the brain where the two optic nerves cross over each other) cut. Because of this, the information from the left eye was only being delivered to the left hemisphere and vice-versa.
*Optic Chiasm*
If you are interested in learning more about the experiments Roger Sperry undertook with monkeys you should start by reading [Split-Brain Approach to Learning Problems](http://people.uncw.edu/puente/sperry/sperrypapers/60s/130-1967.pdf).
Testing Unit described in *SplitBrain Approach to Learning Problems*