[0:00] Memories are biological magic that enable you 
to experience bygone moments – over and over.
[0:07] With them, your mind can encode, store and 
retrieve information about the world and yourself.
[0:12] But memories are not static like photos.
[0:15] Like dioramas made from wax, 
each time they’re under the  
[0:19] spotlight of your attention they 
can melt and change a tiny bit.
[0:23] Which is a bit concerning because they 
are a huge part of what makes you, you.
[0:28] They are the personal lore a lot of your  
[0:30] identity is based on – and the basis 
for your decisions about your future.
[0:35] What does it mean if they change?
[0:37] And more fundamentally… What IS a memory? How 
is a moment in time stored in squishy meat?
[0:45] Your Brain is Weird Madness
[0:48] The human brain is the most complex thing in the 
universe, so we need to simplify quite a bit.
[0:54] Scientific models work but are not 
a perfect reflection of reality.
[0:57] It's a bit like talking 
about elementary particles.
[1:00] But in a nutshell, what makes you think and feel 
is a complex system of about 86 billion neurons.
[1:07] Extremely complex electrochemical root 
systems, sending and receiving signals  
[1:12] through synapses – tiny gaps between cells, where 
an electrical signal is converted into chemicals,  
[1:18] bridges the distance, is received 
and converted into electricity again.
[1:23] This is how neurons talk to each other.
[1:25] And it's a busy conversation because a typical 
neuron is connected with up to 10,000 others.
[1:31] Together they’re a network of 
hundreds of trillions of connections.
[1:35] A hundred times more than galaxies 
in the observable universe.
[1:40] From these connections the 
magic of your existence emerges.
[1:44] To create purpose in this chaos some 
connections need to grow stronger.
[1:48] Whenever two neurons fire at the same time their  
[1:51] synapses change and their 
connection gets stronger.
[1:55] They become buddies if you want, and 
when their buddy calls they join in.
[1:59] If we zoom out, patterns emerge.
[2:01] Dozens or thousands of neurons 
organize into local columns.
[2:06] These columns are very basic 
information processing units  
[2:09] that process a tiny piece of all the 
input coming in from your senses:
[2:13] like dark and light, a location in space, how 
a texture feels, the sound of words and so on.
[2:19] You have columns for sound, images, touch etc, 
all located in different parts of your brain.
[2:25] These columns are the gears of the 
biological machine that is your cortex.:
[2:30] It’s the fundamental hardware you emerge from.
[2:33] Everything you see, hear, or feel causes the gears  
[2:36] to move – which means your 
neurons to fire together.
[2:40] But for you to have a coherent experience,  
[2:42] these very different gears 
need to be connected together.
[2:45] Any moment you perceive is 
made from different parts.
[2:48] As you are watching this video, your eyes 
activate columns for vision and color in  
[2:52] your visual cortex, your ears transmit 
information to your auditory cortex,  
[2:57] language areas are decoding my words, while other 
networks keep track of your body and emotions.
[3:03] All these signals are processed in deeper 
areas of your brain that evaluate them,  
[3:07] boosting what seems important right 
now and tuning out what doesn’t.
[3:12] Vastly simplifying, this concert of all 
these different gears connected by levers,  
[3:16] wheels and screws comes together to create a new 
structure, within your brain machine: The assembly.
[3:22] A new pattern of synchronized activity 
within the grand architecture of your brain.
[3:28] This assembly of very different 
neurons firing together,  
[3:30] is what gives you the experience of 
being a human being in this moment.
[3:35] So the assembly active in your brain 
right now is you watching this video,  
[3:39] hearing my voice and learning about memories.
[3:41] But this is only activity 
without permanent substance,  
[3:45] like ripples on a pond, nothing will remain.
[3:48] Without memories you will forever 
be trapped in the present.
[3:51] To become a being that transcends 
time, you need to etch these fleeting,  
[3:56] sensory inputs, these temporary moments, 
into something physical that will remain.
[4:01] And how does your brain decide what becomes 
permanent? With a deadly competition.
[4:07] How To Store The Past
[4:10] In reality there is not just one 
assembly active in your brain.
[4:13] Your brain can’t process everything in the 
outer and inner world with full attention,  
[4:17] so different assemblies 
are fighting for dominance.
[4:19] The details are complicated, but at any moment,  
[4:22] one assembly is winning and deemed 
the most important by your brain.
[4:26] This is what you are aware of right now.
[4:29] In your brain, the assembly 
processing the sentence I’m  
[4:32] speaking to you seems to be 
the most active and wins.
[4:35] Your brain thinks this matters 
and you are forming a new memory!
[4:39] Two things are happening right now:  
[4:41] The neurons of the winning assembly are bathed 
in chemicals that make them more susceptible  
[4:46] to change and tie them closer together, 
strengthening the synapses between them.
[4:50] And the memory center and librarian of your 
brain – the hippocampus – is activated.
[4:56] The details here are super complicated and 
the exact process isn't fully understood yet.
[5:01] But in a nutshell, your 
hippocampus creates a blueprint,  
[5:04] saving the rough configuration of the assembly.
[5:07] The assembly is saved and put 
on an index with all your other  
[5:11] memories that are associated with 
what was going on in this moment.
[5:14] Like “everytime I was confused by 
something in a kurzgesagt video”.
[5:19] Finally you have a memory!
[5:21] An activation pattern of millions of neurons, 
spanning many different regions of your brain.
[5:26] Activating any part of the pattern now 
makes the whole assembly fire – now you  
[5:31] are able to relive a moment of the past 
that is gone forever in the real world.
[5:36] But this new memory is very 
fragile and still pretty temporary.
[5:40] Your hippocampus holds its blueprint,  
[5:42] but without reinforcement, the assembly will 
fade and the synapses will be weakened again.
[5:47] This is why you forget most moments of your life,  
[5:50] why you don’t remember how your coffee 
tasted 43 weeks ago on a Monday.
[5:55] You experience most of your life 
only once, in the moment you live it.
[5:59] And you don’t just forget what happens to you 
– you also forget what happens in the world.
[6:04] Most news stories disappear within days,  
[6:06] and often you never even saw the 
full picture in the first place.
[6:09] This is why we’ve partnered with Ground News,  
[6:12] a media literacy tool whose 
mission we fully support.
[6:15] Their app and website let you compare coverage,  
[6:18] explore context and see how 
stories spread over time.
[6:22] You can even see how bias shapes the narrative.
[6:25] Take this study on Alzheimer’s risk in women.
[6:28] More than 40 articles were published on it: some 
focus on how menopause shrinks parts of the brain,  
[6:33] others highlight the benefits of hormone therapy.
[6:35] You’re actively weighing 
different aspects – and that  
[6:38] deeper engagement helps your brain to remember.
[6:41] Most importantly, Ground News reveals "blind 
spots" – stories that only one side is covering,  
[6:46] showing you what your usual news feed is hiding.
[6:49] As information bubbles become the norm, thinking 
critically about the news is no longer optional.
[6:55] And Ground News makes it easier to do just that.
[6:58] Try it via the QR code on the screen or 
go to ground.news/nutshell.
[7:03] Our link below gives you 40% off 
an unlimited access subscription,  
[7:07] and directly supports our channel.
[7:10] And now, back to your brand-new memory!
[7:13] For the past to be truly saved, the 
assembly needs to fight for its life.
[7:18] There are many ways this can happen:
[7:20] One of them is novelty.
[7:22] If you walk to the bus, listening to 
some mildly interesting podcast as usual,  
[7:26] this assembly’s signal is too weak.
[7:29] This moment in time will be 
lost, like tears in rain.
[7:33] But if one day you see a crow and 
a squirrel fighting over a nut,  
[7:36] only for a mouse to steal it – the assembly will 
fire strongly just for the novelty of it all.
[7:42] Another one is to reactivate the memory 
over and over after it is formed.
[7:46] Thinking about the animal fight all 
day and telling everyone about the  
[7:49] strange event will etch it deeper into your brain.
[7:52] Similar to doing loads of repetition 
when you try to learn something.
[7:56] And a major way to make a memory 
stick is to feel emotions.
[8:01] Emotions are really strong mechanisms  
[8:03] to guide our behavior that evolved 
hundreds of millions of years ago.
[8:07] They motivate you to avoid danger, 
seek out food and reproduce.
[8:11] You experience this as 
something feeling good or bad.
[8:14] Whenever you feel something strongly, your 
ancient brain decides that whatever is going  
[8:18] on is important for your survival, 
regardless if it's wrong or not.
[8:23] So many of your strongest memories 
have strong emotional flavors.
[8:27] The humiliation when you acted 
dumb in front of your crush.
[8:30] The joy when you beat your dad at Mario Kart.
[8:33] The devastation when your dog died.
[8:36] The overwhelming love when 
you held your first kid.
[8:40] If we just made you feel something, we increased 
the chances that you will remember this video.
[8:45] Strong activation, repetition and 
emotions do the same thing to your memory:  
[8:49] We said before that chemicals made the neurons 
able to change – well now they change drastically.
[8:55] Like wax warming up and melting together, 
the gears of the assembly grow new teeth  
[9:00] to fit more tightly – neurons grow more 
synapses and fire together even better.
[9:06] They become closer and more solid.
[9:08] A lot of this happens while you sleep.
[9:10] Your hippocampus replays the assembly over and 
over, making it more solid and easier to retrieve  
[9:16] – which also means that if you don’t sleep 
enough, you literally forget more of your life.
[9:21] Think about that when you have to study for 
a test next time – without proper sleep,  
[9:25] you’ll be wasting your time.
[9:27] But in the end you have a proper long term memory.
[9:30] A diorama of hardened wax, 
displaying a moment of your life.
[9:34] A scene etched into a pattern 
of connection inside your brain.
[9:38] Now you can remember it forever! Well…
[9:42] Why Remembering Changes Your Memories Forever
[9:45] To remember you need a cue for the memory, 
something that is part of the original assembly.
[9:50] A smell, sound, word or maybe 
the image of an angry crow.
[9:55] Your hippocampus searches its index for the cue,  
[9:57] hopefully finding the right 
stored assembly, and activates it.
[10:00] It fires.
[10:02] Your past experience is retrieved.
[10:04] The diorama appears in your mind and you 
relive seeing the crow and squirrel fighting!
[10:09] So far so good.
[10:11] But as the diorama plays for 
you, you start changing it.
[10:15] Recalling memories is not like 
loading a video and pressing play.
[10:19] Under the light of your attention 
parts of the wax become soft again.
[10:22] Moldable.
[10:23] Which means that as you experience 
the memory in your mind, the neurons  
[10:27] involved are bathed in chemicals that make 
them able to change their structure again.
[10:32] Your hippocampus organizes memories based 
on a few things but most importantly:  
[10:36] the context of the experience.
[10:38] And the context is now very different.
[10:41] When you formed the memory you were tired, in a 
mildly bad mood before work and very surprised.
[10:46] Right now you are pulling the memory as you 
are having a night out with your friends  
[10:50] and are telling them your hilarious 
story of the epic squirrel crow fight.
[10:54] And this new context seeps into the memory.
[10:58] New connections form, some synapses 
are weakened while others reconfigure.
[11:03] The diorama changes, becomes 
funnier and more absurd.
[11:07] Not because you want it to,  
[11:08] your brain is just incorporating the new 
context of your life into the memory.
[11:13] As you finish your story, the 
light of your attention moves on,  
[11:16] the diorama hardens again, now in a new form.
[11:20] The next time you remember the animal fight,  
[11:22] you will remember it as way funnier 
than when you actually experienced it.
[11:26] And it is the same with all your 
memories – when you retrieve them,  
[11:29] your brain adds new information or forgets some, 
and incorporates your emotions and expectations.
[11:35] In a sense it updates your past life to 
fit the narrative of your present life.
[11:40] Over time, even core memories can shift, combine 
with others, or generate entirely new elements.
[11:46] Your memory system is deeply intertwined with 
the mechanisms for learning – it was never  
[11:51] designed to create an accurate 
representation of the world.
[11:54] So your memories are updated as you 
gain new experiences and information.
[11:58] Ironically, the more you 
remember something actively,  
[12:01] the less of the original experience remains.
[12:04] This also means that just because you remember  
[12:06] something really well it does 
not mean your memory is correct.
[12:10] It just means that its assembly 
is really strong and vivid.
[12:14] It’s not a sudden process, your 
identity is safe for today.
[12:18] It is a slow shift in the overall 
patterns inside your mind.
[12:22] You are who you are today, but your 
future self will be different and  
[12:26] they will think and feel differently 
about the things you experience today.
[12:31] This is also why therapy can be so helpful.
[12:34] By revisiting hurtful memories in a safe context,  
[12:38] ideally with helpful introspection, 
you are literally changing your brain.
[12:42] Literally rewiring yourself 
to get a chance to be happier.
[12:46] Because yes, your memories may be the lore 
of your life and the basis for your future.
[12:52] But it turns out, with some help you may be able 
to rewrite your lore and be who you want to be.
[13:02] And if you want to rewrite the lore of your home,  
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