Engrams: Where Your Brain Keeps Memories


[♪ INTRO] When you want to remember where you left your
keys, you will, hopefully, conjure up a sort of image or idea of where
you last had them. While it may seem like that memory just magically
appears in your mind’s eye, the truth is that memories are far more physical. That means they have to live somewhere in
your brain. But, like, where? Is there a shelf labeled
“keys” right next to the one that says “that time I tripped and fell down during
the school play”? Well it’s definitely not that literal. But thanks to advances in neuroscience, we can finally pinpoint the actual location
of a memory; at least if you’re a mouse. To find a memory, first you have to make one. And it’s easy to do that, you just do something. Anything, just like, watch me do this! That’s
in your brain now! You’re stuck with it! Your brain will then pick a bunch of cells
to store a memory of the thing you just experienced, and it
will activate them all at the same time. But those cells aren’t all in the same place, because the parts in your brain specialize
in different things. Your brain will pick cells across regions
to store all the different aspects of a memory. For example, neurons in the visual cortex
will store what you were seeing, and the cells in your amygdala will store
how you were feeling. That specific pattern of cells, all firing
together, is what the memory is now, in all of its multisensory glory. The word scientists use to talk about this
physical trace of a memory in a brain, the pattern of cells that activate to recall
a memory, is an engram. It’s the unique pattern of cells activating
together across the brain that makes a memory. And these cells are actually changed by the
learning experience. They form stronger connections with each other
than with other neurons and they develop more dendritic spines: protrusions
that help neurons talk to each other. So how do you find an engram? Ideally, if you could watch neurons fire, you should see the same ones fire when the
same memory is activated. And we can do that in mice. In a 2007 study published in the journal Science, researchers taught a mouse to associate a
mild foot shock with a sound. This is a pretty commonly used protocol for
studying memory. If you see the mouse tense up, you know it
remembers a shock is coming. And don’t worry, it’s just, it’s like
a little zap. The researchers used a special glowing protein to tag the neurons that fired as the mouse
learned. That let them monitor what neurons fired when
the mouse heard the tone and remembered what was coming next. A few days later, when the researchers played
the sound again, they saw the same neurons firing. Basically, they saw that memory. Now the next question was whether altering the neurons in the engram would mess
with the memory. Which would prove that those neurons were
holding that memory, and could even lead to, like, memory editing. So in a 2009 study, also in Science, researchers
infected an area of the mouse’s brain with a virus that increased both how readily
those neurons would activate, and the number of those neuron-connecting
dendritic spines. The virus basically made this area full of
“super-neurons,” which the researchers hoped would be very
likely to be used for storing a memory. Then, the researchers once again taught a
mouse to associate between a sound and a foot shock, and then, just as planned, the super-neurons
were used to store that memory. But the virus also had a kill-switch, which
the researchers activated after training. Like a tiny viral assassin, it took out the
super-neurons. When they played the sound again, the mouse
didn’t freeze up. It seemed to have no idea that a shock was
coming. It appeared that killing those specific cells
also killed the memory. In subsequent research, scientists were able
to manipulate both real and false memories. In one 2012 study, the researchers used a
technique called optogenetics, where, by shining a special light on a part
of the brain primed with light-sensitive proteins, you
can turn specific neurons on. The researchers taught a mouse to associate
a sound with a shock and then pumped the engram cells, where they knew that memory lived, full of
this light-sensitive protein. When they turned on the light, the mouse acted
like it had just heard the sound and expected a shock, even though there was
no sound. And in a 2013 study published in Science, researchers moved a mouse from an old cage
to a new cage, and trained it to fear that new cage with
electric shocks. Then, they used similar optogenetic techniques
to make the mouse remember its old cage while it was in the
new one. When they put the mouse back in its old cage,
it still seemed frightened; it thought that was where the shock had happened. These findings might make it seem like neuroscientists
are officially masters of memory, able to edit, implant,
and delete memories at a whim. But it is very early days here. We’re nowhere close to handheld memory wiping
gadgets à la Men in Black. But, if manipulating engram cells can add, delete, and modify memories in predictable
ways, that does mean engrams are a useful model
for studying memory. Memory is such a crucial part of our lives
and our identities, and by better understanding how it works physically, we demystify it. That could open the door for better treatments
for conditions like Alzheimer’s or post-traumatic stress
disorder. So while we will probably never have zappers
to remind us where our keys went, we are getting closer to understanding how
our brains store the memories that make us, us. Thanks for watching this episode of SciShow
Psych. Did you know you can help us make fascinating
videos about science that are free for the whole Internet to enjoy? Because you can, if you become a patron! And if you do, you will be joining an amazing
community of people, and scoring neat perks like behind-the-scenes
bloopers. I had some in our recent episode about robots.
I got real mad about a thing. If you’re interested, head over to patreon.com/scishow. [♪ OUTRO]

100 thoughts on “Engrams: Where Your Brain Keeps Memories

  1. Is conscientiousness extremely complicated or is it super simple and radical? Basically, can we chip away at figuring it out or do we just have to come up with an explanation in one fell swoop?

  2. Man, I’ve been curious about where a memory “lives” and from one-word into the title i learned more than my 10 years of aimless Internet searching

  3. I watched this then forgot it so watched it again, im good until tomorrow then I’ll forget yesterday and watch it again, what m i typing about?¿

  4. Yo, what if in Men in Black, all the minds are altered to react to the flash of light. So they forget everything from the last few Minutes and there brain is rewired in a way that the memory gets rewritten to what had been told to them.
    And the length of memoryloss is proportional the amout of IR or UV idk

  5. Personally, I've always viewed my brain like an internet. It's a system with built in fault tolerance and memory redundancy organized like a wiki. This seems to heavily support that.

  6. All this is to say, humanity is one step closer to getting rid of that awful memory I have of a nightmarish movie about a homicidal rat named Ben.

  7. playing with memory editing…no big deal. nothing to see here, folks. nope. nothing bad could possibly come from this knowledge, someday. not at all.

  8. They can create a virus that can turn your neurons into super neurons? Why isn't this being explored for its medical uses in humans?

  9. I described a lot of my missing memories (from PTSD) as being in a box. Usually as a joke, you know, like "bad memories get put in the time-out box". However, doing this for 24 years seems to have had the side effect of… ruining my memory. I look forward to seeing how our understanding of memory progresses in the future.

  10. Our understanding of psychology and neuroscience when I was studying psych in highschool: we literally have no idea where memories are stored, maybe that the hippocampus and the amygdala are involved

    Us now: SO

  11. Maybe theirs more then one copy of the same memory.
    Cells have memories maybe memories are imprinted on proteins

  12. Scientists: drag Povlov for his unethical experiments

    Also scientists: Let's give this mouse PTSD and then delete its memory lol

  13. The problem with manipulating memories the further back you go the more likely your going to change their expression and perhaps personality. I'm conflicted about zapping my PTSD away.

  14. what a wonderful episode about dispassionately torturing animals…

    …it would be a great deal more useful to stop all invasive and painful animal research now and replace it with more basic human research which has a disproportionately larger payoff and usually translates 100% of the time instead of only 5% of the time.

  15. Mentioning an image of where you left your keys reminded me that I have aphantasia. About four years ago you did a video on this subject. Anything new that might be worth a followup?

  16. I have internal organs that = the age 80 year old, so my insides are dying faster then my outside appearance, so yeah.

  17. “One of the great challenges in NDT fandom is realizing that he knows enough to think he's right about everything but not enough to realize that he could be wrong about everything” – me

  18. L Ron Hubbard spoke of Engrams in Dianetics which eventually became Scientology.
    Doing an Audit gets rid of the emotional charge attached to traumatic memories, and going clear is the objective.

  19. Now that know that each part of a memory is stored in the corresponding area of the brain, they can show you the same thing and monitor whether or not a certain part fires, which indicates whether or not you remember it. Ie, showing a murderer a picture of the victim and seeing if the anger area shows activity, indicating an angry memory related to it. If you're innocent, nothing there should fire

  20. they figured out how to rewrite memory & relocate the target of our trauma in 2009 & 2012 & the CIA told hank he could finally let us in on it cuz it’s too late to stop them now

  21. This reminds me of the book Recursion, by Blake Crouch. It dealt with locating, storing, and re-activating memories. It did, of course, have major consequences, so let's hope it doesn't go that way for us.

  22. What I've learned from this videos is that these researchers may be the precursors to the villain Scarecrow.

  23. The moved the mouse and it was still afraid? Weird … it's not like it was trained to be fear being zapped …

  24. How do you find an engram you ask? I remember a time when you could kill hive in a cave. Enough kills produced an engram… the good o'l days.

  25. Now : : I wait for the engram research to include a cellular matrix brain scan and backup ability to ensure a clean saved state of a mind. Digital consciousness 1 step closer ;))))

  26. There’s a really interesting way sleep interacts with this memory process as well. My last video talks about it if anyone’s interested.

  27. My lab does research in this exact field, thank you for shining the spot light on this for a bit. Now I have something to show prospective undergrads. Thank you and DFTBA

  28. I'd be interested to see if the same patterns implanted into a different mouse results in it having the same memory. Can you teach a mouse to "remember" something it has never actually experienced? If so it seems like the very early stages of matrix-like instant learning.

  29. 5:28 – That's great, but I'm more interested in potentially finding a way to digitize memories for both evidentiary and documentary/legacy/backup purposes.

  30. Correlation does not equal causation. Just because neuronal pathways fire when a memory is elicited, does not entail that the memory is stored in the brain. The scientists did not see the memory, they saw a neuronal firing pattern correlative with the memory.

  31. All my life, people have been saying, "it's either this or that," and I have had no idea what "this" is. Now Hank finally demonstrates it and I was in the other room and now I'll NEVER know what "this" is.

    If only scientists were working on a way for me to forget the trauma, but they're doing this instead.

  32. When I hear of all the experiments done to animals all I can think of is the cruelty done to those poor creatures.

  33. Alas, we got a Men In Black reference rather than Lacuna, Inc from Eternal Sunshine of the Spotless Mind…

  34. If a light flashes in a mouse' brain but there's no acoustic vibration associated, does it make a sound?

  35. I've heard (0:07) that the general population can actually do this – see images in their minds.
    And that some people cannot. I'd like to see some scishow about those who can't – and some details about those who can. How clear are the images? etc etc.

  36. Man, science sometimes can depress you; especially research on the brain. We're all just a collection of physical connections in the brain. I mean sure, if you erased all your memories you'd still be alive, but you'd probably just sit there drooling, and not much more intelligent than a baby; more learning capability sure, but no knowledge or experience.

  37. Kinda cool to see this guy still on here. Been a few years already, when it used to be only one Scishow channel. Everyday now, I can go to bed less stupid 😛

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