Do memories occupy a physical space in the brain?
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Logically they do. However it is very hard to identify which neurons take part in which memory. The closest thing we have is the experiences of people who have suffered brain damage in the regions most associated with memory. These are people who have had parts of their brains destroyed. And they often report that various random bits of memory which you would otherwise expect be intact is just gone.
This is a fundamental question in psychology – the touchstone paper was written by Lashley in 1950 called “In Search of the Engram” – here are the two big takeaways:
(1) memories are not localized but are instead distributed within functional areas of the cortex and
(2) memory traces are not isolated cortical connections between inputs and outputs.
A couple of related works:
“Shadows of the Mind” by Roger Penrose, which is less about memory and more about consciousness (the entire field pivoted in the same way).
If that scratches an itch, you should check out “The Self and the Brain” by Karl Popper.
If I’m interpreting your question correctly: No.
Think of how a computer’s storage works first: You can definitely say computer data takes up physical space, and you can even point out exactly where that data exists: it’s in the hard drive. Literal arrays of 1’s and 0’s that correspond *exactly* to the information they represent. This data can be copied, deleted, moved around and changed however you like. Its *tangible*.
Your brain doesn’t work like this at all. Even if you had a perfect understanding of the brain, and scanners advanced enough that you could pick out the tiniest signals inside your brain cells, you would never be able to track down and copy your most embarrassing memory onto a hard drive, and this is *not* just because you don’t have a USB port on the side of your head. You can’t just upload a foreign language into your brain the way you can install an app on your phone, and that’s not just because your brain doesn’t have a wifi antennae. Its because there is no “real” information in your head that can be copied, deleted, or edited like on a computer
I’m not enough of an expert to say exactly how the brain does store memories, but hopefully this contrast with computer memory helps put it somewhat in perspective. The brain is insanely weird.
If you want to learn more, read this:
https://aeon.co/essays/your-brain-does-not-process-information-and-it-is-not-a-computer
Sort of, but with billions of neurons it’s impossible to track it down where a particular memory is.
We know where the different types of memories are mainly due to studying brain injuries. Your working memory is housed in the prefrontal cortex. Episodic and sensory memory will likely be stored in the hippocampus. Not all long term memory is stored there though, it’s believed that some of it gets transferred to the cerebral cortex. An injury to your hippocampus causes amnesia, but you don’t lose everything. I believe more episodic memories stay in the hippocampus.
Now these neurons are only able to be recalled through the paths between the neurons called axons. These neurons will be activated and depending on how much activation will determine the strength of the path making it easier to recall. It’s why you have to recite a phone number (from working memory) over and over, while something traumatic (episodic in hippocampus) will get a very strong activation. You can’t recall every episodic memory because your brain can’t remember the path, just like you can’t remember every phone number.
It’s been a long time since I took neuropsych so take that with a grain of salt, plus I haven’t kept up with the research since which is constantly getting better.
Yes and no. Memory science still has a long way to go, but basically, memories are pathways. I am no expert on the subject, but here is how I understand it:
Your brain is made up of neurons. Every experience you have is an electrical signal passing through some neurons. When you see a dog, specific neurons light up. When you see a car, specific neurons light up. When you see a dog in a car, signals are shared between your dog neurons and your car neurons. If you see a dog in a car every day, the signals being passed between those neurons will form a bridge (called a dendrite) or strengthen an already existing one. That makes it easier for signals to pass between those neurons in the future. More connections means it is easier for a chain of neurons to light up when there may not be a logical reasoning for them to. You may see a blue bike and some electricity from your blue neurons will make its way to your car neurons because you have a blue car so the connection between those two is stronger in your brain. Then, because your car neurons are lighting up, some electricity manages to reach your dog neurons. Now, you saw a blue bike and all of the sudden, you remember the dog in your car.
Memories can also form if there is a lot of different pathways. So, if the dog puked in your car on the way to the park, now you have dog neurons, car neurons, blue neurons, neurons for the smell of puke, neurons for the sight of puke, disgust neurons in reaction to the smell/sight of puke, emotion neurons from getting upset about the puke, neurons about the park, etc. All these things are connected and so each time one of those neurons light up, there is a chance it will activate one or more of the other neurons connected to it. These chance activations also strengthen the connection which helps maintain the memory.
Then, years later after your dog has passed away and someone says “Tell me a memory you have of your dog”, the word “dog” can activate that whole cluster of neurons associated with the event. That activation is you remembering.
I hope that makes sense. Also, like I said, I’m not an expert so if someone on here knows better than me, please share.
The answers to this great question reminds me of the main character from Silicon Valley trying to explain to people how his compression algorithm stores data across everyone’s devices but doesn’t take any space on any of them.
There is no perfect answer to this question because we don’t know enough yet about how exactly everything works in a brain.
We have a lot of good theories, but many things are still fuzzy…
Literally yes, practically no. There’s plenty of space for all the memories you could ever have For the science, see the other poster’s bit on neurons.
As someone who develops AI, this is my take on it.
There are neurons and axons in the brain.
Neurons are like switches and axons are like cables.
A neuron is “switched” when a certain amount of electricity is collected at its input. Just like a real switch will turn on lights when we press it hard enough.
The electricity a neuron outputs will go through an axon to the input of another neuron. A real switch could turn on a light or a small machine which will press another switch using a cable to connect them.
You could actually make a ring out of 3 switches pressing each other. If you press switch A, it will press switch B.
B will switch C and C will switch A again.
Then A will switch B and B -> C.
This will loop forever and this is how our brain might memorize something.
So we would think our memories wouldn’t take up space, right? Kind of.
The amount of electricity going to the other neuron will depend on the thickness of an axon. Just like huge cables are used to transmit gigantic amounts of electricity from one city to another, bigger axons will give space for more electricity to pass.
As our body can grow when we eat enough food, our axons can also grow when we use them a lot.
A short example of why this is interesting:
We have 2 switches:
– Switch A
– Switch B
and 2 cables:
– Cable A
– Cable B
Switch A is connected to a lamp via Cable A.
Switch B is connected to the same lamp via Cable B.
If cable A was too thin, Switch A couldn’t turn on the light, because no electricity would fit through the cable, while Switch B could.
This could impact the circle we talked about earlier.
The switches will only flip each other if the cables are thick enough.
Thus our memory depends on the thickness of axons and they occupy physical space.
Yes and no. In the most abstract sense it’s like storing your data in Amazon’s cloud. You know it’s there somewhere, and it is in principle possible to figure out what set of their hard drives are necessary to reconstruct your data, but in practice it’s impossible to know exactly which ones are involved. You can narrow it down to one or two datacenters, but not to which exact disks.
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