N.G., a housewife from California. She had been suffering from severe epilepsy for years. Her seizures were uncontrollable, affecting her daily life. Medications didn’t work, and she was running out of options. Then, doctors suggested a rare surgery—commissurotomy. This meant cutting the corpus callosum, a bundle of nerves connecting the left and right sides of the brain. It was a big decision, but she took the risk.

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The surgery was a success! Her seizures reduced significantly. She could go about her life without worrying about sudden attacks. But something strange happened—something that gave scientists a fascinating insight into how the brain works.

One day, N.G. was part of an experiment. She sat in front of a screen with a small dot in the middle. The researchers showed a picture of a cup to the right side of the screen. She saw it and said, “It’s a cup.” Simple, right?
Then, they showed a picture of a spoon to the left side of the screen. But this time, when they asked her what she saw, she said, “Nothing.” It was as if the spoon had disappeared!

The researchers had an idea. They asked her to reach under a table with her left hand and pick out what she had just seen. Without hesitation, she grabbed a spoon. Yet, when asked what she was holding, she replied, “A pencil.”

WHY WAS THIS HAPPENING?

Here’s the key: Our brain has two halves, called hemispheres. The left side controls speech, while the right side is great at recognizing things but can’t talk. Normally, both sides communicate through the corpus callosum. But since hers was cut, they couldn’t share information.

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So, when the picture of the cup appeared on the right side, the left hemisphere (which controls speech) could say “cup.” But when the spoon was shown on the left side, only the right hemisphere saw it. And since the right hemisphere couldn’t talk, she thought she hadn’t seen anything! However, the right hemisphere still controlled her left hand, which is why she could pick up the spoon—but she didn’t know why she was holding it!
This experiment, along with many others, helped scientists understand that the two sides of the brain work in different ways. The left side is responsible for language, logic, and analytical thinking, while the right side handles creativity, emotions, and spatial awareness.

The Case of N.G. and the Split Brain -----

SOURCE:
Pinel, J. P. J., & Barnes, S. J. (2017). Biopsychology (10th ed.). Pearson.