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A Few Case Studies

How do we know what different parts of the brain are responsible for? Here are just a few case studies from among thousands that have enabled us to match brain regions to functions.

1. Prefrontal Cortex

Mary was an intelligent, driven college student focusing on long-term goals of medical school and starting a family with her fiancé. Unexpectedly she started drinking, experimenting with drugs, seeing other men and skipping class. An MRI later revealed a tumor in her prefrontal cortex.

What is the prefrontal cortex responsible for?

There’s a sub-area of the prefrontal cortex called the orbitofrontal cortex, just behind the eyes (“orbitae” is Latin for eye socket!). A patient named Elliot had a small tumor removed in that area. Afterwards he was just fine, except for the fact that he would now spend hours choosing which radio station to listen to, which pen to use, where to park in a parking lot, etc.

What is this particular area of the prefrontal cortex responsible for?

2. Broca’s Area

Peter had a stroke that damaged cells in Broca’s area, which is only on the left side of the brain. Peter can understand what is said to him, but when he tries to speak he finds it nearly impossible to say words and put them together to form sentences. Here is Peter describing how he came to the hospital for dental surgery: “Yes... ah... Monday... er... Dad and Peter…and Dad.... er... hospital... and ah... Wednesday... Wednesday, nine o'clock... and oh... Thursday... ten o'clock, ah doctors... two... an' doctors... and er... teeth... yah.” Peter also cannot come up with the names of everyday objects when asked to identify them.

What specifically is Broca’s area responsible for?

3. Wernicke’s Area

Anne had a stroke that damaged cells in Wernicke’s area, which is only on the left side of the brain. After the stroke, Anne could speak with ease...but the problem was that she often chose the wrong words for things and her speech came out as a string of garbled words. When asked to give directions to her house she began by saying, “Every river turn street in the horse red boat.” Anne eventually recovered, and when she did she reported that after her stroke she could hear people speak but could not make sense of what they were saying.

What specifically is Wernicke’s area responsible for?

4. Cerebellum

Amir had lost the ability to ride his bike. He also reported unsteadiness when walking, difficulty in tying his shoes, and even trouble clapping on beat to music. An MRI later revealed damage to his cerebellum.

What is the cerebellum responsible for?

5. Amygdala

After her stroke, Shelley’s family noticed that she was no longer startled by loud sudden noises. She was unlikely to flinch when watching horror movies. She was also unable to notice expressions of fright in other people’s faces. A brain scan detected damage to her amygdala. Some studies of serial killers suggest that their amygdalas have a very low level of function.

What does the amygdala do?

6. Thalamus

Some stroke patients who had damage to their thalamus reported the following unusual occurrence: Sounds sometimes caused a tingling sensation in their skin.There is some evidence that if the thalamus is “over-wired” or maybe is not “pruned” fully that people may develop synesthesia – the blending of the senses. For example, people my feel that smells have a certain color or that numbers evoke a certain color, or even a certain taste. Musical notes might have a certain color, or smell, or taste. In fact, as much as five percent of the population might have a form of synesthesia.

What does the thalamus do?

***7. Corpus callosum

Many years ago, Marco was diagnosed with severe epilepsy (too much electrical activity in the brain, resulting in seizures - unwanted muscle contractions). He underwent a surgical procedure that involved severing his corpus callosum. Shortly after the operation, if Marco was handed, say, a pencil in his RIGHT hand and asked what it was he could say it was a pencil. But if the pencil was put it in his LEFT hand, he could not say what it was. He knew what the object was for, but he just couldn’t come up with its name.

A few weeks after surgery, Marco regained the ability to name objects no matter which hand they were placed in.

What do you think is the function of the corpus callosum?

What does Marco’s recovery from his post-surgical problem tell you about the brain?