The “language” part of the brain, centered in the left hemisphere of the brain, was discovered in the 19th century. It wasn’t until the 1960s, however, that scientist Roger Sperry and his colleagues found that by disconnecting the corpus callosum, millions of nerve fibers bundled together that connects the two halves of the brain and allows for them to communicate with each other, they were able to see exactly how each hemisphere of the brain worked. This discovery is known as “split brain”.

Cutting the connections between the left and right hemisphere of the brain was, at that time, the only cure for patients with severe epilepsy. Too many nerve cells were firing at the same time, creating a “storm” in the brain of the epileptic. Severing the nerve connections calmed the storm, but didn’t interfere with the person’s ability to live a normal life. Each hemisphere was still able to learn and function, but they just weren’t able to communicate with each other, so one side didn’t know what the other side learned.  Now cutting the complete set of nerves is not necessary to eliminate the epileptic’s seizures, only a few connections are severed.

In the split-brain patient Sperry and his colleagues were able to observe how each area of the brain worked independently, and how each side specializes in different tasks. The left side of the brain takes care of the analytical and verbal tasks. It speaks much better than the right side. The right half takes care of space perception tasks and music. It is the side of your brain you use when you are making or reading a map, or giving directions on how to get to your office from home. The right hemisphere can only put together basic words and phrases, but adds emotional context to your speech. Without the help from the right hemisphere, you would be able to read the word “dog” for instance, but you wouldn’t be able to visualize what a dog was.

Patients with split brain gave researchers a real insight into how each part of the brain operates. For example: one of their patients, Paul S., was more developed in language skills before the operation. This helped researchers to interview both sides of the brain after the operation. When asking the right side what Paul wanted to be, he said an automobile racer. When asking the left side he said he wanted to be a draftsman.

Another patient exhibited strange behavior with his hands – his right hand tried to pull up his pants while the left hand tried to pull them down. Another patient argued with his wife, one side attacking her with his left hand and the right hand defending her.

Sperry conducted an experiment where he flashed a word so the right hemisphere of the brain would interpret the information. The patient wrote down the correct word with his left hand, but when asked what he wrote done the patient did not know. Since the brain was split the information that was given to the right half could not relay the message to the left side.

It seems these and other experiments on patients with split-brain definitely indicates that both sides of the brain are independent of each other, but one side definitely has an area it specializes in and is more dominant than the other side. The interesting question is, why is the brain wired this way? Experiments like the split-brain allow scientist to get a better understanding of brain functions, but they are still baffled. What they do know is that we need both sides of our brain to function normally, even if they are not connected.

Roger Sperry won the Noble Prize in Physiology or Medicine in 1981 for his split-brain experiment.

This information is very interesting. It’s always fun to explore the different areas of the brain and how they work. It helps me get a better understanding of how memory is processed, and aids in the development of new techniques that will help people for memory improvement.





Split-Brain Behavior, by Marsha Vasiliadis :

Nobel – The Split Brain Experiments: