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Changingminds writes in Right and Left Brain:

The brain cortex (the crinkly 'walnut' bit) is divided into two clear hemispheres, connected by the corpus callosum, which provides an 'information highway' between them.

The halves are neither mirror images nor contain completely exclusive functions. However there are significant similarities. Each half receive sensory information though, curiously, from the opposite side of the body. Thus the right eye goes to the left brain and vice versa.

Is it true that all the information from the right eye goes to the left brain and vice versa?

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    What I understood: The left side of the visual range of both eyes goes to the right side of the brain. And in reverse. – GEdgar May 19 '16 at 15:02
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    This might be a better fit on Biology. It seems like a clear case of established science, and people over there should be in a good position to answer it. – Reinstate Monica iamnotmaynard May 19 '16 at 15:42
  • @iamnotmaynard : For basic science, biology is a website that's about providing the right answer. On the other hand Skeptics is a website that's about providing the evidence for why a certain answer is right. – Christian May 19 '16 at 15:54
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No, the right half of the field of vision goes to the left brain, and vice versa. A quick search showed up a book by a Harvard professor with this quote:

A massive stroke in the left side of the brain leads to paralysis and lack of sensation in the right face, arm, and leg and to loss of speech. What is less commonly known is that such a stroke generally leads also to blindness in the right half of the visual world—the right visual field— involving both eyes. To test for such blindness, the neurologist has the patient stand in front of him, close one eye, and look at his (the neurologist's) nose with the other eye. He then explores the patient's visual fields by waving his hand or holding a Q-tip here and there and, in the case of a left-sided stroke, can show that the patient does not see anything to the right of where he is looking.

So the effect is quite easy to demonstrate scientifically (an awful lot of our knowledge of the brain comes, somewhat grimly, from studying what happens when you damage bits of it).

The reason they are reversed is actually one of optics, not neurology: light rays passing through a pinhole cross over, and project an image that is reversed both top-to-bottom and left-to-right. So it is actually the left half of each retina which transmits to the left half of the brain, and the nerve fibres which cross (at the "optic chiasm") are the ones closest to the nose.

  • This source is a little dated. Recent research shows that there is some duplication on each side. – called2voyage May 20 '16 at 16:46
  • What always confused me was that it seemed that earlier tests on patients with severed corpus callosums "proved" the "one-eye-one-hemisphere". Always suggested to me that it might be more "all in their head" than originally thought. – Sean Duggan May 20 '16 at 17:09
  • @called2voyage I did wonder if that might be the case, but as a non-expert figured that it was probably "close enough" - Wikipedia seems to agree, although in somewhat impenetrable language. Feel free to add another answer if there's a better description that more closely matches modern scientific findings. – IMSoP May 24 '16 at 15:43

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