Building Blocks of Memory in the Brain

Artem Kirsanov
Artem Kirsanov
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Published 2023-07-06
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My name is Artem, I'm a computational neuroscience student and researcher. In this video we discuss engrams – fundamental units of memory in the brain. We explore what engrams are, how memory is allocated, where it is stored, and how different memories become linked with each other.

Patreon: www.patreon.com/artemkirsanov
Twitter: twitter.com/ArtemKRSV

OUTLINE:
00:00 - Introduction
00:39 - Historical background
01:44 - Fear conditioning paradigm
03:38 - Immediate-early genes as memory markers
08:13 - Engrams are necessary and sufficient for recall
10:16 - Excitabiliy and memory allocation
16:19 - Brain-wide engrams
18:12 - Linking memories together
24:20 - Summary
25:33 - Brilliant
27:09 - Outro

REFERENCES (in no particular order):
1. Robins, S. The 21st century engram. WIRES Cognitive Science e1653 (2023) doi:10.1002/wcs.1653.
2. Roy, D. S. et al. Brain-wide mapping reveals that engrams for a single memory are distributed across multiple brain regions. Nat Commun 13, 1799 (2022).
3. Josselyn, S. A. & Tonegawa, S. Memory engrams: Recalling the past and imagining the future. Science 367, eaaw4325 (2020).
4. Chen, L. et al. The role of intrinsic excitability in the evolution of memory: Significance in memory allocation, consolidation, and updating. Neurobiology of Learning and Memory 173, 107266 (2020).
5. Rao-Ruiz, P., Yu, J., Yu, J. J., Kushner, S. A. & Josselyn, S. A. Neuronal competition: microcircuit mechanisms define the sparsity of the engram. Current Opinion in Neurobiology 54, 163–170 (2019).
6. Josselyn, S. A. & Frankland, P. W. Memory Allocation: Mechanisms and Function. Annu. Rev. Neurosci. 41, 389–413 (2018).
7. Choi, J.-H. et al. Interregional synaptic maps among engram cells underlie memory formation. Science 360, 430–435 (2018).
8. Abdou, K. et al. Synapse-specific representation of the identity of overlapping memory engrams. Science 360, 1227–1231 (2018).
9. Yokose, J. et al. Overlapping memory trace indispensable for linking, but not recalling, individual memories. Science 355, 398–403 (2017).
10. Rashid, A. J. et al. Competition between engrams influences fear memory formation and recall. Science 353, 383–387 (2016).
11. Poo, M. et al. What is memory? The present state of the engram. BMC Biol 14, 40 (2016).
12. Park, S. et al. Neuronal Allocation to a Hippocampal Engram. Neuropsychopharmacol 41, 2987–2993 (2016).
13. Morrison, D. J. et al. Parvalbumin interneurons constrain the size of the lateral amygdala engram. Neurobiology of Learning and Memory 135, 91–99 (2016).
14. Minatohara, K., Akiyoshi, M. & Okuno, H. Role of Immediate-Early Genes in Synaptic Plasticity and Neuronal Ensembles Underlying the Memory Trace. Front. Mol. Neurosci. 8, (2016).
15. Josselyn, S. A., Köhler, S. & Frankland, P. W. Finding the engram. Nat Rev Neurosci 16, 521–534 (2015).
16. Yiu, A. P. et al. Neurons Are Recruited to a Memory Trace Based on Relative Neuronal Excitability Immediately before Training. Neuron 83, 722–735 (2014).
17. Redondo, R. L. et al. Bidirectional switch of the valence associated with a hippocampal contextual memory engram. Nature 513, 426–430 (2014).
18. Ramirez, S. et al. Creating a False Memory in the Hippocampus. Science 341, 387–391 (2013).
19. Liu, X. et al. Optogenetic stimulation of a hippocampal engram activates fear memory recall. Nature 484, 381–385 (2012).
20. Silva, A. J., Zhou, Y., Rogerson, T., Shobe, J. & Balaji, J. Molecular and Cellular Approaches to Memory Allocation in Neural Circuits. Science 326, 391–395 (2009).

CREDITS:
Icons by biorender.com/ and www.freepik.com/
Brain 3D models were modeled with Blender software using publicly available BrainGlobe atlases (brainglobe.info/atlas-api)
Rat free 3D model: skfb.ly/oEq7y

This video was sponsored by Brilliant
All Comments (21)
  • @guilhermesantos7355
    As a Technology and Neuroscience's undergraduate i can say your videos are not only a scientific work but also one hell of a art piece! Thanks man, greetings from Brazil
  • @hackerbrinelam5381
    This is very fansinating, I mean now I know how my brain literally physically learn things, and it makes sense some questions I have on some learning advice, "why do you should learn using most of your senses" "why do you need to focus, pay attention" "why repetition "why you should use your prior exprience to help you to learn" "why do you forget sometimes then remember other times or why you cant retrieve your memory anytime"
  • @iandanforth
    I had no idea that neuron excitability varied with a period of hours! Such an important piece of the puzzle, thanks for this video.
  • @Anatanomerodi
    I recently discovered your videos, and being a Neuroscience PhD student myself, I want to thank you, your work has re-sparked the motivation to read about topics outside my PhD subject, something I was feeling to do for a long time but never found the energy in the day to day of working. The presentation of the topics is excellent, as well as the edition of the videos, thank you very much for these incredible contributions.
  • @joonaskuusisto2767
    I’m studying neuroscience in the context of phase transitions. I sometimes intellectually veer towards AI and general computer science but the brilliancy of your videos rekindles the fire for neuroscience. If only more people with your communication and multimedia skills were involved in neurosci, we’d be marching on towards something marvelous. Public exposure and interest control the funding both in academia and industry, this kind of content has the power to ignite mass movements of brilliant minds.
  • @user-db7ru9cd2d
    Man, this channel is a treasure for someone interested in biology and neuroscience. Thanks a lot for your efforts! ❤❤❤
  • @allanburns1190
    This is one of the best video essays I’ve ever watched on YouTube
  • @VaradMahashabde
    I am always surprised by how beginner friendly your videos are.
  • @tinkeringtim7999
    I would love to see you take a deep dive into cognative/behavioral relationships to engram learning. A lot of people struggling with trauma related memory issues (inc. PTSD) would likely benefit from understanding how their brains physically learned (and could un-learn). In fact, it seems to me many therapists could also do with knowing more about learning and plasticity.
  • @chenmarkson7413
    Second-year uni student here (neuroscience major); I feel like I am watching a spoiler and can't stop myself. This is so interesting, learning about all the progress we have on the neuronal basis of learning and memory. Much much much more interesting than the various theoretical memory models I have to memorize in psychology classes!
  • @cirecrux
    Massive respect for the brain guys who do the brain work
  • @MarkosDrakos
    Such an amazing video on such an interesting field, thank you for this! I've recently studied a module on engrams and one paper I found really interesting - claiming to have satisfied the engram mimicry criterion - was Vetere et al. (2019) - "Memory formation in the absence of experience". I found this to be the most groundbreaking stuff so far, and the only evidence so far to suggest that mimicry may be possible. I'd love to know your thoughts! I'd also love to see a video on the clinically translatable parts of engrams - and the utilisation of the tag and manipulate/erase tools as treatments for OCD and addiction. I also thought this area had some really cool research, and seeing it in video format with your animations and explanations would be really useful!
  • @davidyang102
    The temporary excitability remind me of dropout which is a technique to improve deep learning by turning off neurons randomly. That improves the robustness of the network
  • @eaturfeet653
    My thesis project is very intimately involved with this field, thank you for communicating it so eloquently and effectively
  • @reeb3687
    Do we currently know how brains "check for overlapping" in separate engrams? Also, is it possible for completely unrelated memory clusters to randomly have similar engrams/engram positions, causing them to be intrinsically linked, and, if so, how often/how likely is this to occur?
  • @GeoffryGifari
    nice job man... one of my top youtube sources for up-to-date neuroscience without dumbing down
  • @EMOTIBOTS
    Hi, really interesting to learn about the waxing and waning of neuron excitability. Makes sense why there's just some things that are easier to process depending on the time of day. There's one more thing you can add to the reason why only some neurons are selected for an engram, and that is that when one neuron fires, it raises the action potential of the area outside of its membrane, which in turn locally raises the threshold needed for other neurons to fire. If there are two neurons equal in excitability and one of them happens to fire first, the second one may not fire because of the heightened action potential required. Love watching your videos, very inspiring and well communicated!
  • @icandreamstream
    What an achievement this video is, thanks for taking the time to create this.