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What happens when you remove the hippocampus? - Sam Kean


27,974 Questions Answered

TEDEd Animation

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When Henry Molaison (now widely known as H.M.) cracked his skull in an accident, he began blacking out and having seizures. In an attempt to cure him, daredevil surgeon Dr. William Skoville removed H.M.'s hippocampus. Luckily, the seizures did go away — but so did his long-term memory! Sam Kean walks us through this astonishing medical case, detailing everything H.M. taught us about the brain and memory.

Additional Resources for you to Explore

You can read more on this fascinating case in educator Sam Kean's book: The Tale of the Dueling Neurosurgeons: The History of the Human Brain as Revealed by True Stories of Trauma, Madness, and Recovery.

Henry Molaison was a person who played a key role in helping the world learn essential information about the brain. His sacrifice did and still does not go unnoticed by many people in the neurological community. Listen to an interview of Dr. Milner and Henry Molaison from NPR that details Henry’s story. Now that you have heard Henry in person, do you have any insights about his life?

A major effort was put forth to preserve Henry’s brain after his death. Why is this the case? What could we learn from his brain that we didn’t already know? Why has this had such a massive impact on the neurological community? Listen to an audio segment on Science Friday to learn more!

Here is a scan of H.M.'s brain.

Did preserving H.M.’s brain allow a “look” inside a human brain that we didn’t have before?What would it be like to look inside a human brain? Watch this TED Ed lesson: What If We Could Look Inside Human Brains? to learn more. Take a visual tour of the brain with an explanation of the parts of the brain and their functions here.

How good is your memory? Watch this amazing TED video: Joshua Foer:Feats of Memory Anyone Can Do. Learn some tricks to improve your memory and be amazed at what you can do with your own brain! Exercise it!

Do you wear a helmet when you ski or snowboard, or go biking? Your brain is arguably the most essential organ of your body. How do you protect it? Recent news reports have discussed the effects of concussions on the brain and traumatic brain injuries. Scientists have encouraged the use and development of better helmets for all types of sporting events. Watch this video: Helmets are Cool and learn how wearing or not wearing a helmet can change your life forever.

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About TED-Ed Animations

TED-Ed Animations feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed Animation? Nominate yourself here »

Meet The Creators

  • Educator Sam Kean
  • Director Anton Bogaty
  • Narrator Addison Anderson

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