What happens when you remove the hippocampus? – Sam Kean

What happens when you remove the hippocampus? – Sam Kean


On September 1st, 1953, William Scoville used a hand crank
and a cheap drill saw to bore into a young man’s skull,
cutting away vital pieces of his brain and sucking them out through a metal tube. But this wasn’t a scene from a horror film
or a gruesome police report. Dr. Scoville was one of the most
renowned neurosurgeons of his time, and the young man was Henry Molaison,
the famous patient known as “H.M.”, whose case provided amazing insights
into how our brains work. As a boy, Henry had cracked
his skull in an accident and soon began having seizures, blacking out
and losing control of bodily functions. After enduring years of frequent episodes,
and even dropping out of high school, the desperate young man
had turned to Dr. Scoville, a daredevil known for risky surgeries. Partial lobotomies had been used
for decades to treat mental patients based on the notion that
mental functions were strictly localized to corresponding brain areas. Having successfully used them
to reduce seizures in psychotics, Scoville decided to remove
H.M.’s hippocampus, a part of the limbic system
that was associated with emotion but whose function was unknown. At first glance,
the operation had succeeded. H.M.’s seizures virtually disappeared,
with no change in personality, and his IQ even improved. But there was one problem:
His memory was shot. Besides losing most of his memories
from the previous decade, H.M. was unable to form new ones,
forgetting what day it was, repeating comments,
and even eating multiple meals in a row. When Scoville informed another expert,
Wilder Penfield, of the results, he sent a Ph.D student named Brenda Milner
to study H.M. at his parents’ home, where he now spent his days
doing odd chores, and watching classic movies
for the first time, over and over. What she discovered through
a series of tests and interviews didn’t just contribute greatly
to the study of memory. It redefined what memory even meant. One of Milner’s findings shed light
on the obvious fact that although H.M. couldn’t form new memories,
he still retained information long enough from moment to moment
to finish a sentence or find the bathroom. When Milner gave him a random number, he managed to remember it
for fifteen minutes by repeating it to himself constantly. But only five minutes later,
he forgot the test had even taken place. Neuroscientists had though of memory
as monolithic, all of it essentially the same
and stored throughout the brain. Milner’s results were not only the first
clue for the now familiar distinction between short-term and long-term memory, but show that each uses
different brain regions. We now know that memory formation
involves several steps. After immediate sensory data is temporarily
transcribed by neurons in the cortex, it travels to the hippocampus, where special proteins work to strengthen
the cortical synaptic connections. If the experience was strong enough, or we recall it periodically
in the first few days, the hippocampus then transfers the memory
back to the cortex for permanent storage. H.M.’s mind could form
the initial impressions, but without a hippocampus
to perform this memory consolidation, they eroded,
like messages scrawled in sand. But this was not the
only memory distinction Milner found. In a now famous experiment,
she asked H.M. to trace a third star in the narrow space between
the outlines of two concentric ones while he could only see
his paper and pencil through a mirror. Like anyone else performing such
an awkward task for the first time, he did horribly. But surprisingly, he improved over
repeated trials, even though he had no memory
of previous attempts. His unconscious motor centers remembered
what the conscious mind had forgotten. What Milner had discovered was that the
declarative memory of names, dates and facts is different from the procedural memory
of riding a bicycle or signing your name. And we now know that procedural memory relies more on the basal ganglia
and cerebellum, structures that were intact in H.M.’s brain. This distinction between “knowing that”
and “knowing how” has underpinned all memory research since. H.M. died at the age of 82 after
a mostly peaceful life in a nursing home. Over the years, he had been examined
by more than 100 neuroscientists, making his the most
studied mind in history. Upon his death, his brain was
preserved and scanned before being cut into over 2000
individual slices and photographed to form a digital map
down to the level of individual neurons, all in a live broadcast
watched by 400,000 people. Though H.M. spent most of his life
forgetting things, he and his contributions
to our understanding of memory will be remembered for
generations to come.

100 thoughts on “What happens when you remove the hippocampus? – Sam Kean

  1. Although that operation was a good way to recover from epilepsy, yet it was horrible to remove some important memories. Poor him.

  2. i feel sad for this man, but i'm glad he seemed to have a peaceful life despite the severe memory impairment. we learned so much from him, and we never have to let someone lead a life like that again (at least, not without the patient knowing what the surgery entails).

  3. RIP H.M.

    You may not have memories of your own but I and many others do and you will always occupy a spot in ours.

    Thank You for your continued approval to further scientific research, True Hero.

  4. Frankenstein stop it… Now we discover phills of how to deleted cells and take out into the small robotic medical tools hahaha

  5. Fourteen days passed after making use of this loss of memory treatment solution https://tinyurl.com/memoryloss99 I observed big improvement of my brain capacity to stay focus. Lately, I found out that I can simply recall things and easily comprehend than they do. This is enjoyable, challenging but not annoying..

  6. If his brain was mapped down to the individual neuron, doesn't that mean that a simulation of his brain could be constructed similar to what was done with the open worm project? What would be the ethics of turning his brain on in a simulation built from photos of his neural connections?

  7. On June 25 2013, I had a right temporal lobe, parietal lobe, and occipital lobe resection. That just means that parts, or all of those lobes of the brain, including the hippocampus and amygdala were removed. I was not told of the side effects before surgery, except risk of stroke, death, and infection. And since my seizures were so frequent I thought, what have I got to lose? I didn't know then, that the seizures I had were from a brain hemorrhage I had after I was born. If I would've known that then, I probably wouldn't have gone through with the surgery. I'm adopted, and for whatever reason my parents didn't read the medical part of the adoption papers. But I did and that's how I found out. But that was a year or so after I went through with surgery.  Anyway, long story short. I lost my sight, a little bit of hearing in my left ear, I developed vertigo and balance issues, terrible anxiety problems, chronic fatigue syndrome, memory problems and obsessive thinking. Most of these symptoms I didn't have before surgery except I was already visually impaired.
    The doctors didn't think that me losing the rest of my sight was a big deal since it was so poor to begin with. It was my mom that stuck up for me then, and said that no matter when you lose it, or how much you lose, it's still hard to go through.
    anyway, my memories are vague ones now. Like half there. partially because the left side of my brain wasn't touched. So if someone tells me something more than once, I can remember it. But if someone tells me something one time, more than likely I won't know what they are talking about. when I got home from surgery it was really bad for a while. I couldn't remember what the date was, the day of the week, the last time I took my medicine, or what time it was. I had to be constantly reminded of things all of the time. But things that I had already known how to do I still knew how to do, and still do. It's just learning new things that's hard for me. But I'm too stubborn to give up.
    Our super computers fascinate me. I never cared about psychology or anything having to do with science before surgery and now I'm fascinated by brain anatomy, because when you change and you are learning bout yourself you research and look things up because no one else will tell you. So anyone reading this, just know that if you have to go through any kind of surgery, ask lots of questions before hand and do your research. I did, and I wasn't told the whole truth. but life is too precious. Don't give up and keep trying. Do whatever makes you happy and share your wisdom and love with others.

  8. I want to forget my memories. It's just too horible and i can't bear with it anymore. I would be a willing to be a test subject of any professional doctors who are willing to conduct such experiments like this.

  9. I mean sure he forgot pretty much all of his memories and thus losing a sense of self but his seizures stopped. Sooo the surgery was successful

  10. Just goes to show how much you can accomplish even without giving in too societies expectations of "accomplishing more".

  11. Just watched,Great video, very interesting what happened to him
    now ill think I'll watch this video to see what it's about and to see
    what happened to him

  12. I have slight damage to my temporal lobe (which contains the hippocampus) and one of the things this caused was memory loss. How I would describe it is like the memory isn’t there when I try to remember it. It only really happens when it’s something like going inside to get something or remembering what someone asked me to do. I know that I need to remember it and it’s like searching for it but it’s just out of reach until it’s gone. Usually, if I’m reminded again I’ll remember it.

  13. Why do the people who comment feel pity for this man. I actually want that part removed so I dont have to worry so much about anything and feel happier. Bye bye anxiety. That'd be an awesome life

  14. So why don’t we just remove or modify certain parts of each section of the brain? Because maybe for example: memories won’t need certain parts of the hippodkcjsoaukdifjxkc. Probably the stupidest thing to ask but whatever.

  15. Having had a severe brain injury at 15 where my short term memory was all but useless; I can tell you how frustrating forgetting stuff is! I improved after I was given; Harry Loraynes; "The memory book"…. just an FYI to those out there wishing to regain some ability to remember.

  16. We are saying R.I.P. like we have baby pictures on our fridge of HM. we all just found out through a poor drawn cartoo, that was about His life. His life was interesting but to say R.I.P. like I know know him is lame. Lucky for him he doesn't remember dying.

  17. And they can use that information about memory to manipulate memory in any subject of their choosing. Which has already taken place btw. Ever hear of the Mandela effect?

  18. Apparently after H.M died, he woke up 5 minutes later as if nothing had ever happened, because he forgot that he died.

  19. Apparently after H.M died, he woke up 5 minutes later as if nothing had ever happened, because he forgot that he died.

  20. Apparently after H.M died, he woke up 5 minutes later as if nothing had ever happened, because he forgot that he died.

  21. I once saw a documentary about this man. The saddest thing that sometimes happened to him was that he saw himself in a mirror and that he wouldn't see himself, a young man, but an old man. When he realised he was the old man infront of the mirror he started crying. Fortunately he forgot about that after 15 minutes.

  22. Wow
    Cracked scull as a child
    Ruined teens
    And seizures
    Removal of hypo campus
    No
    Seizures
    Forever more
    Also no mems
    A life of a different type of repetition
    With limited mem
    Until 82
    Death
    Then finally a object of scientific study
    Forever
    😳😢😣😢🤧
    I hope one of those final mems was knowing God

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