Book & Brain – Can we ‘see’ memories in the brain?

Yesterday I wrote a review of the book ‘Before I go to sleep’ which left me with many questions about memories. How are they formed in your brain, how do we store them and what happens if memories are lost.

Memory is the faculty of the brain by which data or information is encoded, stored, and retrieved when needed[1].

What kind of memories are there?

Well, just to be completely honest about the title, ‘memory’ is a very exciting part of the study of our psyche but it is also not easy to do research on it. A lot we still don’t know and there are many, many sorts of memories. There is an individual one but also collective memory exists. You hold on to written or heard information but also smell and touch can trigger memory paths. And of course you ‘remember’ every day how to ride a bike, how to hold your arms in regards to your body and how to speak. Things you don’t really think about are stored in your implicit memory while your test answers would be in your explicit memory. You could also hope that those answers initially would be stored in your short term memory only to be kept in your long term memory.

How do memories form in your brain?

Memories are a physical thing, they live somewhere in your brain. Neuroscientists can pinpoint the actual location of a memory in mice. First of course you need to make a memory. Look outside your window for example or … read my post, that is a far better example! Maybe now you’re smiling. Let’s keep that memory in mind. Your brain will pick a bunch of cells to store that memory and activate them at the same time. The wonder here is that those cells aren’t all located at the same space but are scattered throughout your brain [3]. With your memory came the event of my silly joke and maybe your reaction – like smiling or rolling your eyes, this happened at a certain time and at a certain place. All this information is stored at the same time in different locations of your brain. Neurons in the visual cortex will store what you were seeing and the cells in your amygdala will store how you were feeling. Those cells firing together is what the memory is now. This pattern of cells that form and can recall a memory is called an engram[2].

Picture credits, click here.

Is your memory static?

No, the cells involved in a memory can change by the learning experience. The connection becomes stronger like a road that you often walk, will have your footprints on it. The neurons involved will develop more dendritic spines, which help the neurons to talk to each other. The road becomes more and more carved.

Can we see engrams?

Ideally we should see the same pattern of neurons making the same connection while you retrieve the same memory. When you rehearse something over and over again, it becomes easier to retrieve that information, right? In 2007 researchers did see that happen in mice. Mice heard a sound what was followed by a mild shock. Through repetition the mice learned to expect the shock after the sound. Then they were injected with a glowing protein to make the connections in the brain visible. After a few days the mice heard only the sound, they tensed up and researchers could see the path in the brain again. They saw that memory of the sound and its consequences.

Picture credits click here.

Can we ‘mess’ with memory?

What if we messed up the neurons involved in a memory, we alter the engram, would that effect the memory itself? Spacey question, isn’t it? A study in 2009 proved that when you kill off the specific neurons involved in a memory, the memory does disappear. Mice[3] once again were taught (making engrams in the brain) to expect an electric shock but once the specific cells we’re killed off, they didn’t freeze up!

They also reversed the study and through activating specific neurons the mice we’re ‘told’ that a sound was coming, they froze up[4] but in reality there was no sound at all[5]. They put that memory straight into the brain of the mice if you will. Talking about amnesia research found that once memories are stored, they can become ‘silent’. Through activation[6] of specific neurons memories came back, what wasn’t possible with external cues like smell, sound, language etc.

What does this mean?

Let me start by making it very clear that this doesn’t mean that researchers can put, add and delete memories from a human or your brain. What is does mean is that studying engrams is useful when we want to know more about memory. Further research could help gaining insight for different illnesses such as Alzheimer disease but also for PTSD. What this could mean for treatment of PTSD in particular, you can read here: How associative fear memory is formed in the brain.

Thank you very much for reading. Were you surprised at all of what is possible in ongoing research in regards to memory?

Notes, recourses and references.

[1] https://en.wikipedia.org/wiki/Memory

[2] Term introduced by Richard Semon in the 20th century.

[3] We can’t compare a rodents brain very easily to a human brain. It is not that easy to assume that all that is possible with a human brain too.

Localization of a Stable Neural Correlate of Associative Memory

[4] Liu, X., Ramirez, S., Pang, P. et al. Optogenetic stimulation of a hippocampal engram activates fear memory recall. Nature 484, 381–385 (2012). https://doi.org/10.1038/nature11028

[5] Creating a False Memory in the Hippocampus.

[6] Memory engrams: Recalling the past and imagining the future

Schiller, D., Monfils, M., Raio, C. et al. Preventing the return of fear in humans using reconsolidation update mechanisms. Nature 463, 49–53 (2010). https://doi.org/10.1038/nature08637

Online article. Medicalxpress.com. Researchers find ‘lost’ memories using light.

19 thoughts on “Book & Brain – Can we ‘see’ memories in the brain?

  1. The science of memory is so interesting, as is the way memories can become inaccessible. My grandma has dementia and she can’t remember what you told her 30 seconds ago, but she can recite a poem she learned in school 90 years ago.

    Liked by 1 person

    1. I hope science one day will be able to help people better with alzheimer, dementia and so on. I believe that the research that is done here is very promising but also at the beginning stages.

      Liked by 1 person

    1. That is exactly what I found while reading further into the subject. The problem isn’t the storage of the memory but the recollection of it.
      And indeed every ‘memory’ is so very personal as the individual ‘stores’ all the information that is important to him/her at the moment. Things like good/bad smell or eye contact can mean the world for one person and do nothing for the other.

      Liked by 1 person

  2. I’ve always found this fascinating, both as a journalist who has strove to tell the “objective truth” while recognizing no human can actually do that and as a lucid dreamer/sleeper who sometimes can’t tell if he’s awake and which memories are real and which were just made up in a more subdued state of mind.

    Liked by 1 person

  3. This was so good! I’m reading about Complex PTSD and they write a lot about emotional memory where you’re not having visual flashbacks but something triggers and emotional flashback. It is fascinating all that is stored in our bodies. Thank you for such a thorough article on all you’ve learned

    Liked by 1 person

    1. You’re very welcome, thank you for reading and commenting! Emotional flashbacks is something that I experience in my dreams now. All different ‘dreamy’ situations but the feelings are the same. Very strange because I don’t dream often. Memories can be so complex.

      Liked by 1 person

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