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Stories of Cancer Research. Driving Discovery. Of course, these are generalizations and in normal people, the two hemispheres work together, are connected, and share information through the corpus callosum. Much of what we know about the right and left hemispheres comes from studies in people who have had the corpus callosum split - this surgical operation isolates most of the right hemisphere from the left hemisphere. This type of surgery is performed in patients suffering from epilepsy.
The corpus callosum is cut to prevent the spread of the "epileptic seizure" from one hemisphere to the other. Roger Sperry who won the Nobel prize in and Michael Gazzaniga are two neuroscientists who studied patients who had surgery to cut the corpus callosum. These studies are called "Split-Brain Experiments". After surgery, these people appeared quite "normal" - they could walk, read, talk, play sports and do all the everyday things they did before surgery.
Only after careful experiments that isolated information from reaching one hemisphere, could the real effects of the surgery be determined. Sperry used a tachistoscope to present visual information to one hemisphere or the other.
The tachistoscope requires people to focus on a point in the center of their visual field. Because each half of the visual field projects to the opposite site of the brain crossing in the optic chiasm , it is possible to project a picture to either the right hemisphere OR the left hemisphere.
So, say a "typical" language in the LEFT hemisphere split-brain patient is sitting down, looking straight ahead and is focusing on a dot in the middle of a screen. Then a picture of a spoon is flashed to the right of the dot. When the person is asked what the picture was, the person has no problem identifying the spoon and says "Spoon. Now if the person is asked what the picture was, the person will say that nothing was seen!!
But, when this same person is asked to pick out an object using only the LEFT hand, this person will correctly pick out the spoon. For example, most people are either right- or left-handed , as opposed to ambidextrous.
Scientists used to believe that the asymmetrical nature of the brain was unique to humans, but this assumption started to change in the s, when several studies showed that such asymmetries were also found in other animals, such as chaffinches a type of small bird , and rats and chickens, according to the review.
And more recent research has shown that such asymmetries in the brain and behavior can be found even in invertebrates such as worms, slugs and honeybees, the researchers wrote. Still, much more research needs to be done to fully understand the intricacies of brain asymmetry, the researchers said. The data suggest that when both hemispheres have some competence at a difficult task, there is a benefit to interhemispheric interaction.
The role of the CC in the dynamic distribution of attention may be particularly relevant to this advantage. Throughout the article reference is made to individual differences and developmental changes associated with interhemispheric interaction.
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