Ologies with Alie Ward - Mnemonology (MEMORY) Part 1 with Michael Yassa

Episode Date: December 4, 2024

How are memories made? Where are they stored? Where do they go? What was I just talking about? Neurobiologist, professor, researcher, and Director of UC Irvine’s Center for the Neurobiology of Learning and Memory, Dr. Michael Yassa, joins us for a two-parter deep diving into our memories. Get to know the cells that run your life while he also busts flim-flam, and talks about movie myths, aging and memory loss, childbirth amnesia, what happens when you cram for a test, hormones and memory, that thing where you can’t remember a word, how to let go of the past, and more. Next week, we’ll follow up with your Patreon questions about Alzeihmer’s, remembering people’s names, neurodivergence, dementia, collective misremembering, and so much more. Commit it to memory.  Follow Dr. Yassa on Google Scholar and XVisit the Yassa Translational Neuroscience Laboratory at UCI websiteA donation went to UC Irvine Center for the Neurobiology of Learning and Memory’s graduate student and postdoctoral fundMore episode sources and linksSmologies (short, classroom-safe) episodesOther episodes you may enjoy: Attention-Deficit Neuropsychology (ADHD), Molecular Neurobiology (BRAIN CHEMICALS), Eudemonology (HAPPINESS), Traumatology (PTSD), Sports & Performance Psychology (ANXIETY & CONFIDENCE), Phonology (LINGUISTICS), Neuropathology (CONCUSSIONS)Sponsors of OlogiesTranscripts and bleeped episodesBecome a patron of Ologies for as little as a buck a monthOlogiesMerch.com has hats, shirts, hoodies, totes!Follow Ologies on Instagram and BlueskyFollow Alie Ward on Instagram and TikTokEditing by Mercedes Maitland of Maitland Audio Productions and Jake ChaffeeManaging Director: Susan HaleScheduling Producer: Noel DilworthTranscripts by Aveline Malek Website by Kelly R. DwyerTheme song by Nick Thorburn

Oh hey, it's the fountain at the mall that's never on. Allie Ward, and you're here for your brain, so am I. Let's get into it. So thisologist was recommended years ago and has been on my list forever, but I wanted to scoot on down an hour south of LA to his office on the UC Irvine campus, where he does a lot of very cool and important work studying brains. How does one become that? Well, an undergrad in neuroscience and a

master's in psychological and brain sciences from John Hopkins University where he was later an assistant professor. He got his PhD from UC Irvine and then he returned there to become the director of the Center for the Neurobiology of Learning and Memory. Dude knows memory. Everyone in his office was so nice, and I got there, we posted up at his desk, and at one point, I looked over to see some artwork of a seahorse, and I was like, okay, and then I realized, oh, okay,

we're gonna touch on that in a bit. But first, thank you to all the patrons who submitted questions for this episode, which we're gonna cover wall to wall in part two next week, and this, because this is just a huge topic. There's so many good questions. Thank you to everyone getting all of these merge from all of these merge.com. Thanks to everyone leaving us reviews, which boosts the show so much.

And each week I remember to read them all. And I pick it just written one such as this one from Lucy goose, who wrote that they drove for seven days to Alaska from the lower 48 States. And all of these made the 10hour days pass quickly. Lucy Guse, I hope we saw a moose and now onward. Okay, nemenology is not a word that this guest really likes because someone else wrote a book using it, he has nothing to do with the book and that person's Google Alerts, RIP, it's going to get screwed up because of this. But nemenology is the study of memory.

And it comes from the Greek for something used to help in remembering a thing, which is what I suppose your brain's function is, among other things. So let's get into how it does that, as well as discuss movie myths, aging, and memory loss, childbirth amnesia, where your memory is stored, what happens when you cram for a test or a presentation, hormones and memory, the movie Lucy, how to know if you're losing your mind, that thing where you can't remember a word, what memory is

even for, how to let go to the past, remembering people's names, neurodivergence, collective misremembering, dementia, Alzheimer's, and so much more with neurobiologist, professor, researcher, director of UC Irvine's Center for the Neurobiology of Learning and Memory, and, I'm sorry, nemanologist, Dr. Michael Yasa. And I'm going to make you hold your mic a little bit like this. Dr. Mike, what do you prefer? Mike is perfectly fine. I am not very formal at all. I'll just call you Doc.

How's that? I think anything aside from Mike would just make me feel very strange, but Doc is fine. Doc is fine. It's okay. As someone who studies memory and neurobiology, do you get put on the spot a lot about memory?

Do you tell people at dinner parties what you do, or will you just be diagnosing people without you wanting to? Oh my gosh, if the question comes up like nonstop, the minute I say that I'm a neuroscientist or I study the brain, even if I don't say anything about memory, the first thing they'll tell me about is how poor their memory is. Of course.

Or they'll ask me about what is this thing that happens when I just have this thing at the tip of my tongue and I just can't come up with it, and then all of a sudden when I'm not thinking about it, it comes to mind. I'm like, yeah, tip of the tongue phenomenon. I try to tell them a little bit about how that works. We'll get to it. So it's a great conversation to have on a plane at a dinner party, but it's nonstop.

Everyone wants to find out about their brain. Do you ever tell people that you do something else? Well, it's interesting. If I tell them I'm a professor, then I have to explain, well, I do a little bit of teaching, but really I'm doing mostly research, right? But I think that that's sort of a secondary thing they think about in terms of professors, but really you're there to teach. But I quickly pivot from what I teach to what I do research on. And then the interesting questions come about. Sometimes people will tell me about family

members or we'll ask all sorts of interesting questions. And every now and then something out of left field. I'll give you a great example. This is one of my favorites and it's now come up several times when they asked me about whether there are memories that are stored outside of the brain, in the heart or in the liver or some other body organ. And the first time that I heard that question, I didn't know what to do with it. I sort of laughed and thought, okay, you must be joking. And then I looked it up. And there's definitely some folks who do think that. And it's not clear exactly what's happening. They talk about like transplant cases. But at the end of the day, we have to be simplified a little bit in our thinking. This is science and all of the data that we have on memory

and how it works emanates from the brain So that is where things live So I've heard those cases where I never liked donuts before I had a kidney transplant and it turns out they loved donuts and things like that or Somatic memories or somatic therapies and researchers call this clinical manifestations of body memories. And one 2021 study, insular cortex neurons encode and retrieve specific immune responses found that the brain's insular cortex stores immune related information and that in mice, those who had episodes of this induced colitis for the study could re

experience that intestinal inflammation just by having the insular neurons reactivated. And the 2022 paper, Clinical Manifestations of Body Memories, the Impact of Past Bodily Experiences on Mental Health, cited that study and explained that the findings indicate that memory alone can activate the immune system in the absence of an outside trigger. So in other words, the brain remembered an old infection and generated the inflammatory disease on its own by reactivating a specific memory trace of the past bodily immune response. And as will not surprise you, there's a lot left to research in this realm and it's fascinating. But wait, what were we talking about?

But I want to go back to the tip of the tongue phenomenon because that was one of my questions. Of course, I mean, I can maybe with a little bit more detail later, but I can tell you that it's a very innocuous thing. It doesn't mean anything is wrong with your brain. It doesn't mean that it's on a decline or anything like that. It happens all the time and largely

because we are distracted. And there are many things that are competing for our attention at any given time. Even thoughts in our brains constantly compete for attention. So every now and then you have sort of a little bit of a failure of recall. You know, the memory is there, but it's an issue of access and you have to kind of clear some of the clutter to be able to access it appropriately. And a lot of times that happens when your brain quiets a little bit, when you're not distracted by the current things that are happening in the conversation,

that's why it comes back later when you're sort of least thinking about it. Of course, your brain doesn't actually stop thinking, but it surprises you sometimes when it comes up later. So this phenomenon of something being on the tip of your tongue is called tip of the tongue phenomenon according to a 1966 Journal of Verbal Learning and Verbal Behavior article titled, The Tip of the Tongue Phenomenon. But it's also known as lethologica and according to this 2024 paper, Coordinating Words and Sentences, Detecting Age-Related Changes in Language Production, sure it can become more common as we age, but it's also very normal and can be considered just the I'm tired and I have

too much going on in my brain right now phenomenon. But we'll get to memory loss later. We're just getting started and this is a two-parter. Does meditation help your brain if you can try to calm it or quiet it? Yeah, that's a great question. So meditation has a lot of benefits for the brain. Certainly to be able to remove distractors, to think a little bit more coherently about major things that are occupying your consciousness, it helps you do that. I don't know if there's

any rigorous studies that have been done on whether or not meditation, for example, helps with the tip of the tongue phenomenon, particularly because it's difficult to elicit, right? It's like when it happens, you're surprised by it and you say, oh, that just happened, but you can't exactly trigger it in a laboratory setting and study it in detail that way. So we have to just rely on when it happens, like we ask, well, what's the circumstance? What is the situation that you're in? And my guess is if one could do a rigorous study, you would see that meditation likely helps with that.

I'm finding it does happen to me more and more often as I'm older where I'll hear a song and before I could tell you exactly who sang it and now I go, eh, eh, eh, and I can't and I'm wondering in that moment if my brain is just like a bruised apple just full of spots. That's a good one.

I've never thought about a bruised apple analogy before, but you know, you mentioned as we get, and I think that's part of it, but we're also busier and our sleep gets disrupted and all sorts of things. I mean, just think about the 24 hour news cycle and all the things that are constantly competing for our attention. So we've become just in general, much more distractible. I think this generation of teenagers and children, even more and more distractible. So that this generation of teenagers and children, even more and more

distractible. So that likely will happen more often, even absent any sort of aging phenomena. But as we get older, our ability to be able to function and notwithstanding all of these distractions also becomes more difficult. Well, as a neurobiologist, someone who is such an expert in this field, is now a good time to be studying memory because things are changing so much with our attention in our brains? Or is it so frustrating because it changes based on like the TikTok algorithm? So when I first started to get interested in neuroscience, it wasn't clear to me how

quickly our knowledge would change. Now, of course, when I teach students in undergraduate courses, I always tell them, look, I'm gonna tell you mostly textbook versions of things, but there are many things that are past the textbooks, like these textbooks are already obsolete by the time they're coming out, because neuroscience advances so quickly.

So what I tell you is likely gonna be right like 90% of the time in 90% of cases, but there's that additional really interesting 10% that we've essentially just tossed out the textbook over the last few years Wow, and that continues and it actually continues at a very rapid clip so I've been doing this for almost a quarter century now and Then the last five years the advances that I've seen in neuroscience and the study of memory have been so much more substantial than the previous 20 years. And that's because our technology is better, our equipment is better,

the ability to record from more cells in the brain at the same time, and our ability to process just incredible amounts of data with artificial intelligence, machine learning, soon quantum computing. All of those advances have had a tremendous impact on how quickly this field has moved. So I used to be able to tell people, here's what I anticipate will be the case in five years. Now I can't do it anymore. I just, I cannot predict because every time that I've tried, I've realized five years later, wow, we've moved so much faster than I ever anticipated. So if you ask me what I think is gonna happen in the next five years of neuroscience, I have no idea.

The sky is the limit. Is it limitless? Okay, we're gonna get to some whack brain movies in a bit as well. But yes, neuroscience is moving faster and faster and faster as our brains are also getting more and more crowded with distractions and information every day.

We're just zooming on this motorbike of knowledge in the fast lane, carrying all our luggage on our backs. I'm so tired and scared. Well, we don't know the future, but what about the past? How did you become a brain doctor? How did you become someone who wanted to research the brain using your brain? Yeah, it's like, why do I want to think about thinking? There's something so very beautiful and meta about this. You know, it wasn't always something that I envisioned myself doing.

So when I was an undergraduate first starting out, I did my undergraduate training at Johns Hopkins. And I was a pre-med major. That's what a lot of students go there to study. And you have this idealized version of the future, right? I want to be a doctor. I want to help people. And I remember very vividly two things happened in quick succession when I was in my sophomore year of college. I took a class in the Department of Cognitive Science called Minds, Brains, and Computers.

And I remember this so vividly because 1999 was the year that the first Matrix came out. And one of my assignments for that course was to go watch The Matrix. Now at the time I thought, okay, this is crazy. I'm being asked to go watch a movie for an assignment. What could be better? This is like the best life of an undergraduate. So I went and of course, if any of your listeners haven't seen The Matrix, it's a must watch, especially the original. The Matrix is the world that has been pulled over your eyes to blind you from the truth. And it was transformative because I think one of the major themes was could you understand

the brain and its functions so well that you can build a completely artificial simulation of the reality around it and the brain wouldn't know the difference. So it would be immersed in exactly the same way. It would have no idea that this is actually an alternate reality or a simulation. Now that requires that you understand the brain at a fundamental level so well that you can fool it into believing this is a reality. And that was part of the assignment is, you know, what do we need to understand about the fundamental rules of brain operation

to be able to enable something like the matrix. And the notion, of course, of like living in a simulation was just so interesting. At times I still think maybe, maybe, I have no idea. I hope so. But it was at that moment that I realized, you know, as a pre-medical student who's interested in studying biology, studying the human body, all of those things. And this was my first foray into the brain. And I was captivated by the fact that we just had no idea. Yeah.

We weren't even close to having a complete understanding of how the brain operates. We understood a lot about the heart, about the lungs, about the kidneys. You have a pump in the heart, right? You have a filter in the kidneys. And yes, we just put out an episode about veins and arteries. And also, we have one about in the kidneys. And yes, we just put out an episode about veins and arteries, and also we have one about

kidneys and pee. Now there's so much we don't know about the human body and quantum physics and how long we'll survive as a species and if there are aliens, but let's just try to stick right now to the bowl of oatmeal that you think with. But with the brain, it seemed like we knew a tiny fraction of a fraction of what we need to know to really fully understand it. So that became really exciting. And then I started working in a research laboratory in the Department of Psychiatry.

So I started to see patients with a variety of brain conditions. And I was an assistant on a number of research projects where I got to see the impact of what brain research could really allow us to do. So shifted gears, didn't want to go to med school anymore. I was captivated by the thought of I wanted to be a brain scientist and spend the rest of my life doing this because I think I can make a career out of it and study it for a good however many decades without really getting to an end point. And I was also always and continue to be a perpetual student.

So the idea that knowledge is going to evolve and change, that wasn't as scary to me as it might be for maybe some others. So that's what got me into it. And now, you know, 25 years later, I can say, like, we know a lot more, but it still remains a small fraction of what we stand to know. When you were studying neuroscience, and you were studying how memory works, did you have any hacks to remember what you were learning? This is your way of asking me, what can I do to improve my learning? A little bit. So yes, there are a few things, but interestingly enough, we knew those not based on neuroscience.

We knew it based on mostly experimental psychology. I got to do that episode. So psychologists for the longest time, since the 1800s, have been very, very good at trying to understand how to optimize our memories, how to think about forgetting, why does forgetting happen and so on. Now neuroscience gives you tools to understand the mechanisms that lead to that, and that's really important of course for us to be able to change it and optimize it and intervene and certainly in the context of diseases that's important.

But in a day-to-day sort of learning setting, most of what we know still goes back to experimental psychology. I'll give you a couple of examples. One is what we call the spacing effect. So when I teach students about this, I tell them, this is my no cramming rule, right? And the idea is that if you stack all of your learning into one learning episode, you may do well if you're tested say an hour later or two hours later, but you're going to quickly forget all of that material. Oh, cool. And that's why cramming doesn't work for the long term.

Although, and I shouldn't maybe say this, but I'll disclose it anyway, if you really want to do well on an exam, still it does work to some extent, but if you have like a cumulative evaluation in that course, you know, best of luck. So spacing your study sessions becomes really important. And some of that also is how much learning your brain naturally does when you're sleeping at night. It's constantly replaying memories of things that you've learned during the day and trying to consolidate that or kind of solidify it and make it resistant

to forgetting. Yes, rest is important for remembering stuff. So the more that you interspace your study sessions and you have like some sleep in between them the better off your learning is going to be for the long run. So that's one that we've known for some time. The other one that is really, really cool actually comes from the notion that has been entertained I think in the education realm for some time. It's the idea that you may be a visual learner or like an auditory learner or kinesthetic learner and the reality is

that this is all myth. There is no such thing as learning styles. I know and you're giving me the same exact look that I get when I talk to teachers. The reality is if you do the right experiments, you'll uncover the fact that there's no such thing as a learning style. Now what is the case is that the more senses that you involve in your learning, the more you engage what we call multimodal learning. So both visual and auditory and maybe kinesthetic, the better off your recall is going to be later on.

And this can also be called multimodal learning theory, but author and Harvard developmental psychologist and research professor Howard Gardner founded this theory decades ago of multiple intelligences, which breaks down strengths in areas like physical movement and being word smart and nature smart and photo smart and interpersonal smart and some educators have adopted parts of that multiple Intelligences theory to teach using various senses to appeal to different types of intelligence But many researchers are very squicky about that including Gardner himself So while the notion of learning styles are a myth, engaging more senses can help with

recall. Because you're engaging more of the senses, you're essentially giving your brain more bits and pieces to connect this memory to. So any number of those bits and pieces can re-trigger that memory and allow you to recall it. You're giving it more routes to retrieval essentially. So that's something else. Again, we've known this from experimental psychology. We didn't need neuroscience. We didn't need fancy brain imaging and so on to tell us all that. We just knew it simply from practice and behavior. So that's another

really fun one that I realized early on. Well, let's get down to what memory is and where in the brain it's stored. I know the hippocampus is very important. So the hippocampus is a googly little C-shaped part of the brain. It's tucked into the temporal lobe. Actually, you have two of them. And the hippocampus is a major part of the system that makes short-term memories into longer-term ones and damage to it via something like Alzheimer's disease

can result in memory loss and dementia. But a more funner fact is that hippocampus means seahorse because if you were to take yours out of your brain, it would resemble a seahorse or like a very big chicken embryo, kind of a lumpy head region and a weird long tail. It's very slippery looking. But what parts of our brains are we filing it and how does it stick? Yeah, so the question of where does memory get stored and there's a number of answers to this. It all depends on the type of memory. It turns out that memory is not one size fits all.

So remembering our conversation that we're having now, say tomorrow, that's one type of memory. It turns out that memory is not one size fits all. So remembering our conversation that we're having now, say tomorrow, that's one type of memory. But remembering how to tie your shoelaces or how to ride a bicycle, that's a different kind of memory. And it tends to engage different systems in the brain. So there are procedural things that take a lot of trial and error and practice that tends to get stored in some systems in the brain, typically not the hippocampus actually. And then there's experiences that are somewhat autobiographical or what we call episodic memories. Memories for events that happen, people that you meet, names, faces, all this kind of stuff. And that does rely on the hippocampus, at least initially. Over

time, memories tend to get strengthened and the hippocampus starts to create connections with essentially everywhere else in the brain. So that memory has become much more resistant to loss because they're stored in a much more distributed way throughout the brain. So when you ask the question, where do memories get stored? I asked the counter question, which is, where does it not get stored? It's sort of everywhere, right? And depending on the kind of memory, some regions may be more involved than others.

But the reality is all of your brain is capable of what we call plasticity, which is essentially changing the way it functions or the way that it connects with other regions and other cells as a function of learning, as a function of exposure to something in the environment, something that's happening in the world. So memories are less like one big overflowing treasure chest hidden in a specific crawl space of your brain. It's more like if a shipwreck scattered coins all over the beach of your consciousness. So you might have a memory of a chocolate sundae you had when you were 12 after a baseball game

and it might be in one part of your brain, it might be in the occipital lobe or the temporal lobe. Yeah, so let's take that example. That's a great one. So if you think about that ice cream sundae, It might be in the occipital lobe or the temporal lobe. Yeah. So let's take that example. That's a great one. So if you think about that ice cream sundae, the experience of having that, certainly there were visual elements looking at it. Maybe the person who bought it for you or whoever it is.

There may have been some auditory things that you might link to it. If it was a baseball game, there may be some things happening around it. Certainly there's the taste and the memory of that as well. There's an emotional context that might have been such a pleasurable experience that kind of generated some emotional reaction that you maintained. All of those bits and pieces are stored in different places. It's all over the place.

And the hippocampus is actually really good at sort of bringing it all together, right? Not just when you're learning, but a lot of times when you're retrieving later on. And let's say I were to put you in the MRI scanner and ask you to bring back that memory, hippocampus lights up like a Christmas tree. But other places in the brain light up as well. So it creates and holds onto this beautiful conjunction of where the bits and pieces of memory are stored.

And it acts as kind of the thing that brings them together. We call it an index. It's the thing that kind of collects the bits and pieces of memory. So that particular memory would be stored pretty much throughout the brain, but the hippocampus is what brings the pieces together into one solid component.

So I guess let's say like the hippocampus is kind of a metal detector helping gather all that memory treasure on your beach. Also I'm about to try to impress Mike by saying a lot of brain words. So a quick neuroanatomy lesson here. Now a nerve cell or a neuron or a neuronal cell is according to the National Institutes of Health a type of cell that receives and sends message from the body to the brain and then back to the body and messages are and then back to the body. And messages are sent by a weak electrical current.

Now, a nerve cell, it looks kind of like a tree. It's got a long trunk in the middle and some branching, fingery things on one end. Those are aptly called dendrites because dendro means tree. And then the trunk part is called an axon. And where the roots would be are the axon terminals and nerve cells receive signals on one end and then pass them to the next nerve cell and so on and so forth and that little gap between

the two cells that they toss signal over is called the synapse. Now surrounding all these nerve cells are glial cells and those are brain cells that are not neurons and there are a few different types of glial cells. And those are brain cells that are not neurons. And there are a few different types of glial cells. We used to think that glial cells were just kind of like hung out near nerve cells like wing men. But it turns out that they can have a lot to do with how information gets processed and they can affect synapses.

And again, different types of glia. Microglia are the brain's immune cells. Macroglia, like astrocytes, help modulate the levels of neurotransmitters around those synapses. So let's hear me, a podcaster, try to just talk shop with someone who has spent decades studying the most complex aspect of our existence. And what about different types of neuronal cells? What about glial and microglial and neurons and dendrites? Does science know yet what's firing off? We have a good inkling, I think, as to how memory could be instantiated in some of those structural features. But I should still say we still don't fully know. I love that. So we have some ideas, we have some thoughts, and the ideas have been corroborated for many years now.

And one particular facet is if you look at how memories can be stored, at least, and if you were to create maybe a cellular form of memory, how can that be stored? It's in the connections between brain cells and not in the brain cells themselves necessarily. So the idea is that if you're a brain cell and you're talking to another brain cell, there's a certain strength of communication. So as one cell fires what we call action potentials to communicate with the next cell, so that's the electrical firing that happens,

that happens at a certain rate and it's a certain level of communication. If the cells learn something new, you can change the strength of that new, you can change the strength of that connection. You can change the firing rate. You can change whether or not that cell is able to trigger the other cell that it's communicating with. So how strong that ability is to toss a signal from one axon terminal to the branching, fingery dendrites of the next cell. Now, some cells, they might lob it softly with T-Rex arms,

while other connected cells might deliver reliable fastballs, which would be TLP, or long-term potentiation. And that we've known about for quite some time. Since the 70s, we've suspected that the phenomenon called long-term potentiation is a cellular form of memory. Now, since then, we've uncovered a whole bunch of different other kinds of cellular type memories.

But the problem is these are laboratory phenomena. So until you're able to record directly from a brain cell and another brain cell in a live-behaving animal and see that change, which is very tricky because you don't know exactly where the action is going to be. You can guess as to you might put your electrodes in the hippocampus, for example. But again, the hippocampus has millions of cells and you don't know which ones are going to be the active ones. So those neurons, the ones with the dendrites on one end, the long, chunky axon, and the

little root-like axon terminals, you have 86 billion of those in your brain, and you'd have to be looking right at one as it changes with a memory. Now I crunched some numbers. Let's say the average haystack is five feet by six feet, and it weighs 1,700 pounds. So to find and look at the actual neuron sending and receiving signals when acquiring a memory, you would need to, in the blink of an eye, find a needle in 47,000 haystacks. It is difficult. Neuroscience turns out is hard.

But so far, the evidence all points to changes in synaptic strength or changes in the connections between cells. That's where memories seem to be stored. Now you brought up another really interesting point, which is what about other what we call non-neuronal cells like glia or microglia or astrocytes or maybe things that are sort of outside of the cell or outside of synapses. And the answer is, oh, it gets complicated. It gets super interesting because we used to think that those cells are just there for support. And now we recognize that actually those cells

do communicate and do play a really interesting and not very well understood role in some forms of communication across cells but also across each other. So the idea that glial cells, for example, or glia, have their own transmitters, have their own messengers, is one that is actively being studied now.

So I think, again, we go back to how much do we know? Well, it's a fraction of a fraction, maybe five, 10% of what we stand to know. And when it comes to glia, we're nowhere near. So we still have a lot more that we need to learn. And as long as we're talking five to 10%, you want to just bust the myth right now that we only use 10% of our brain or not?

Yeah, let's go ahead. Okay. All right. This is another one that I sometimes will hear. If I could just unlock a little bit more of my brain, come on. If you only had access to 5% to 10% of your brain, guess what? Only 5% to 10% of your brain would actually survive. The rest of it would just atrophy and go away.

You're done with it, right? So brain cells need to be used constantly for them to be able to survive and thrive and do well. And I know this has been talked about in Hollywood. I was just rewatching Lucy the other day. Oh no. There's a few of those terrible, terrible movies. Why? Why did you do that?

I know, it was just on TV. I couldn't help it. It is estimated most human beings only use 10% of their brain's capacity. Imagine if we could access 100% interesting things begin to happen. There's a number of these Hollywood blockbusters out there, whether it's you take a pill or some drug that unlocks the full potential of the human brain. And I'm not saying that, you know, there aren't drugs that can improve function, optimize function,

or give you a boost and all that. Sure. But the idea that you're kind of stuck using five to 10% and if you could just unlock like 90%, you'd be this superhuman entity or no. We use all of our brain all the time. And it really depends on what it is that we're doing at any given time, what that dynamic balance is. And also all brain cells have kind of a basal level of firing of activity. And sometimes that's meaningful, sometimes it's not meaningful.

It's just kind of noise that sits there. But they have to be active in some respects, otherwise they wouldn't be useful. And you know, you said something about superhuman strength, but I know that there are some people whose memories are just bonkers, super, or what is it, hyper? Highly superior autobiographical memory. The fact that that was on the tip of my tongue was just like putting me in an MRI. Well, I'm glad you asked.

So I happen to know something about those folks because we studied them at UC Irvine. And they were first identified actually by my colleague who's now an emeritus professor, Jim McGaw, who built the center that I now currently direct. Ooh, okay, bring it on. And just a quick primer, only about 100 people on Earth have been identified as having highly superior autobiographical memory, where they can vividly recall nearly every day of their lives. And this syndrome is also known as hyperthymesia,

which means excessive remembering. It's just, it's a lot. There's a reason, though, why people want to study them. So, they're interesting. I don't know that I can tell you for sure whether or not their brains are all that different from yours and mine. But certainly their ability is different.

So the first time that one of them was encountered by Jim McGaw, she was able to recall just an incredible level of detail from her childhood and teenage years. He was able to corroborate that to the extent possible using her diaries and then went through an almanac and named off a whole bunch of different events and she gave them the exact dates. One time she came up with something and it wasn't the right date from the almanac. Turns out she was right, the book was wrong. So it truly is incredible and many have been identified since and we've worked with a number of them to try to understand this incredible phenomenon.

Now I should say, I should backtrack a little bit and say, why is this incredible? Why is it so difficult for a scientist to believe this is the case? And that's because for many, many decades, we believed that memory is highly fallible. It's not intended to be very accurate. It's intended to be kind of an estimation of reality. We forget things all the time. We make mistakes all the time, and that's all part of a healthy adaptive memory system because it never evolved to allow us to retain perfect records of the reality around us. We evolved to find berries and to work well with our peers, but maybe not to remember every lyric

to obscure Lionel Richie songs or the password for your cable provider login. And there were stories that were told. Alexander Luria, a famous psychologist, talked about one of his patients who had perfect recall and you would think that this person would be very sort of well adjusted, but he wasn't. He had a difficult time with people around him in social settings and so on. So it seemed like having this perfect memory was not desirable.

It was almost as bad as having a very poor memory. It was extreme. So according to the paper, The Mind of a Nemanist, this subject in Alexander Luria's study was able to recall autobiographical information since one year of age. And the way in which he described his excellent memory was using a kind of grouping of the words,

like quote, the distribution of houses in a street. But he also experienced a type of crossing of the senses, which we're gonna get to later in this episode. And the first thought as a scientist is you go, wow, that's unexpected. This shouldn't have happened, right? If we think about things in terms of evolutionary standards that have kind of got us to where we need to be because it promotes our survival, this should have never happened.

There's no rationale, there's no reason why would this happen to somebody? And yet there they were and they weren't maladjusted. They weren't not thriving. Some of them, obviously there's variability, but many of them were thriving and doing very, very well. Many of them were celebrities, many of them hosted radio shows, did all sorts of things where they sort of leveraged it, they capitalized on this incredible memory. So this kind of took us down a little bit of a different path to say, well, wait a minute,

maybe our understanding of what memory should do is not what it truly is. We always thought that it's supposed to be able to, you know, have an abstraction of reality but not be perfect. Well, in situations where it's perfect, how do we make sense of that? Why is that the case? And we still don't know the answer, but they are one of the most interesting groups of individuals that we study. They're very generous with their time, and we're still kind of at the very beginning of trying to understand what that means for us. If you're like, wait, I have that, or my aunt is weird like that, UC Irvine Center for Neurobiology and Learning and Memory has this easy screening questionnaire.

We'll link it on our website, and they might want to talk to you. But again, it's really rare, and also no cheating by looking at your calendar or your phone's camera roll. I hate that I even have to say that. Also, don't be so quick to envy people with hyperthymesia. Studies show that they don't get to just ace like every trivia round or DMV test they take. Their memories are usually strongest

just in personal details of their lives. Now, in a minute, we'll get to all kinds of juicy gossip about your memory, but first, let's donate to a cause of theologist's choosing. And this week, Mike asked that his donation donation as well as his honorarium go to his lab's fund to help graduate students. And this donation to the UC Irvine Center for the Neurobiology of Learning and Memory will help fund attendance at scientific conferences and seminars and support graduate student and postdoctoral training. Now find out more at the link in the show notes and

thank you to sponsors of this show for making that gift possible. Okay, back to the basics for this part one. And next week, it will be all your questions, patrons. But let's chat about serotonin and dopamine and other brain sauces that keep us alive and remembering. And what about the roles of neurotransmitters? So what happens to the average person if you're talking about the role of neurotransmitters? So what happens to the average person, if you're talking about the role of neurotransmitters

and say memory storage, the way that we think about communication across brain cells is the combination of electrical and chemical communication. The electrical communication is the action potential, that's the electrical signal that goes from the cell body all the way down, what's called the axon, it's sort of long projection, all the way down to the synapse. Okay, remember that's the dendrite, which has kind of the egg yolk-looking cell guts, and then there's the trunk, the axon, and the root-looking things, the axon terminal, and those toss that electrical signal to the next dendrites, kind of like a daisy chain.

But what it allows to happen in the synapse is the release of neurotransmitter. So that's where the chemical part of that communication is. And then the neurotransmitter binds, connects with receptors on the next cell and triggers an action potential there and you get the whole thing to propagate once more. So you have kind of electrical really fast, chemical a little bit slower, electrical again really fast and so on. What happens when you have plasticity is the amount of neurotransmitter that is released

can change or the number of receptors that are able to bind that neurotransmitter on the receiving cells change. Now, neuro nerds know that there has been a big debate about which is the business end of a neuron. Like the body that they control, does a neuronal cell have its own head and butt? Some thought that the receiving end,

that root ball axon terminal, is where the action is, because the surface area of it allows for more neurotransmitter to bind it. They thought the axon terminal was at the wheel here, but other said that it's the yoke cell guts on the dendrite or the dendrite branches themselves that are signaling the amount of neurotransmitter released. We need answers here. In reality, it turns out both happen, of course,

and they're both different kinds of plasticity. One is presynaptic, one is postsynaptic, one is before, one is after. And it's not clear exactly when one happens versus the other, but both of those seem to be heavily involved, and both of those seem to lead to this kind of plasticity, or what we call cellular memory.

And what about the role of dopamine? For more on dopamine, you can see our ADHD episode with Dr. Russell Barkley or the fantastic molecular neurobiology episode with Dr. Crystal Dilworth, aka Dr. Brain. When it comes to attention and forgetting where things are or keeping track of time, things like that, does dopamine play a big role in that as well? It's really interesting you ask me this question now. Because if we did this a couple of years ago, I would have given you a very stereotypical answer

as to the role of dopamine. Dopamine is what we call a neuromodulator. It is not necessarily the thing that makes memory happen, but it can improve the quality of memory storage. It can change that sort of context Especially if it's learning through Reward so like feedback driven learning when you get an outcome says you did this right or you didn't do this right So you kind of learn as a function of that feedback dopamine seems to be involved in that

But in the last couple of years things changed a little bit dopamine started to become even more interesting So in addition to the kinds of roles that we talked about, it seems to have this much more directed role also on the hippocampus in its ability to store memories. It turns out that some types of memories seem to be dependent on dopamine rather than just modulated by dopamine. You need to have dopamine there to be able to have that memory effectively stored and be functional So I think we're again an example of how we're changing our knowledge. If you look at the textbooks What is the role of dopamine very stereotyped answer? You're very much linked to reward learning feedback driven learning

But the data that's been accumulated since and it's maybe not in the textbooks yet Is there's these additional roles for dopamine that are just now beginning to be understood. So dopamine is more than just a motivator. It can actually affect how memories are stored. So there's an ADHD link. But what about for people who also, let's just say, have anxiety? So the HPA access or the hypothalamic pituitary adrenal glands, that is like a three-part click of the endocrine system

that fires away hormones like cortisol and adrenaline in fight or flight mode when you're scared of like a raccoon in the alley or a date or you're tardy for a dentist appointment and the receptionist is mean. And hormones, the endocrine system, the HPA acts, all that plays a role in neurotransmitters, right? Does that mean that hormones play a role in our memory a lot?

Absolutely. Especially when you think about the HPA axis. When you think about, say, hormones like cortisol and corticosteroids, which is the version that's released in the brain, that does have a direct effect on memory. And it can change memory. And there's sort of an optimality. It can change it for the worse in the case of like extreme stress but it can also improve the quality when it's sort of an acute you know small level of stress because

stress is one of those things where some of it is positive too much of it is obviously very negative. For more on what's called you stress we have a whole episode about happiness with Dr. Laurie Santos or huh we have one on burnout with Dr. Candy Wien's so good one on burnout with Dr. Candy Weins. So good and bad stress, your brain begs you to know the difference. So that's one that's pretty well known. There's a number of other hormones also that have an effect on memory storage, and we're still learning about how that impacts brain function and hippocampal function.

Estrogen is one of them. Uh-huh. And we're learning a lot more now about how estrogen impacts the way that the hippocampus is able to store memories and of course how that's different across the sexes and also how it changes as a function of aging as we get older. The fact that estrogen isn't more studied in terms of brain function. I went through ovarian failure really early in my 30s and didn't realize how much it was affecting my memory.

I thought I was absolutely having early dementia because there were a few times I would write my address down wrong or I would give someone information. I always could remember my hotel rooms when I would travel. And there were a few times before I got an estrogen therapy that I was like, what is it? And I was like, oh, no, I'm losing my mind. Yeah, I mean, it's incredible how crucial it is to memory and how drastic the impact

of removing estrogen or changing estrogen function as a function of age, menopause, that has a real effect. And you're right, it is amazing that this is just now starting to become studied extensively. I think that there's a lot of positive things that have happened in the field recently that have led to that, women's brain health initiatives. But for the longest time, we had a major problem in neuroscience and in biology in general, where most of the work in animal models, for example,

was restricted to males. I hate it. And there was sort of this silly excuse of, well, males are just easier to deal with and we have a lot of complexity in female animals and refusing to deal with this complexity. But it's a very cheap excuse, right? And when you think about what we've learned since the National Institutes of Health mandating

doing studies across both sexes, you start to elucidate all sorts of really interesting things about the biology of the system that you would have only learned when you started to study females and do it in a rigorous way. And it's also giving the illusion that males don't have variability. Of course they do. And of course they have hormones. And of course they have very different levels that need to be studied as well. So this is about doing better science, more rigorous science broadly.

And this matters because many studies have shown that women and people assigned female at birth are actually humans who exist. And let's also be honest, we're all freaked out about losing memory as we age, unless you think it would be cool. Like every day is kind of a neat little surprise. Now, does Doc think hormones are a factor in that? So most of my work in the lab is with humans. When you think about postmenopause changes in estrogen levels and hormone levels, most people tend to think of it as like a precipitous drop and a decline.

But even if you study people in their 60s and 70s, there are really interesting individual differences in levels of estrogen at that stage. And those differences in levels also are associated with their memory function and associated with all sorts of things that are changing in their brains. So the nuance continues to be there. And even just if you're curious about the science, really interesting findings that are surfacing. Well, in the last 300,000 years, did we just not really evolve to be this old?

Where does memory and evolution play a part? And age? I mean, some people say that they can remember their birth. Other people are like, it was all a blur until I was like 12, man, I don't know what happened. So evolutionarily, what's going on? Yeah, the evolution story of this actually is very interesting. And it's one that may surprise you, because we tend to think of memory always as a thing of the past, like we need to be able to remember. You just named a couple of examples, even remembering birth.

Now, I don't know that anybody can actually remember that. But certainly people claim to have very strong memories, even from an early age. In reality, your brain systems are still wiring up during development. So a lot of times those memories don't get held onto. There's a phenomenon called childhood amnesia, for example, where we know that those things are just not stored in the kind of high fidelity that you expect later memories to be stored in.

And we forget a lot, right? So why would evolution sort of wire or select for, rather, a system that is so fallible, that is so, you know, error-prone? And the answer is a little bit maybe of a surprise, which is that memory never evolved to study and remember the past. Wait, so memory is not for thinking about the past. Memory did not evolve for us to be able to reminisce and tell stories and think about our past history. The only reason it evolved to be what it is today is to allow us to make

decisions that are better for us in the future. So it's all about survival. And if you think about it from that context of this system has been wired over generations and generations to maximize our ability to use past experience to inform future decisions so we can promote our survival, you become a lot more tolerant of errors. It's okay because I don't need to have a perfect recall of the past. I just need to know that bears are bad or this is a poisonous berry bush or those kinds of things, right? And I also need to know about the positives.

Some things are going to be rewarding. Some experiences I want to have again and again because they were very rewarding in the past. Likewise, your past is only there to guide your future. You can, but you are not obligated to dwell on the past and carry it like an ox hauling a wagon of sad nostalgia. So that's what sort of motivates our memory systems, right? Being able to use that past experience, generalize and extract knowledge from those experiences, things that you can apply to be able to make

better decisions in the future. Not about reminiscing, not about storytelling. However, there's a caveat to this. As a species, humans are very social and we love to tell stories. So I will not dismiss the possibility that perhaps a side effect of this evolution of memory and the telling stories does have a social bonding value and that in and of itself also promotes at least a group survival. And at the individual level probably also because we know that one of the best things you can do for yourself as you get older is maintain some social structures and be social

around others. That seems to be protective almost as much as physical activity, for example. Okay, so for making better decisions and telling jokes and having a kiki. What about age? When do you find people are able to recall some of their first memories? Typically, so if we're excluding people who have this highly superior autobiographical memory where it's like every day for, and even then it starts in their teenage years. Typically you have periods in your life where you have better memories for events that happened and then periods of your life that feel like

it was a blur. Let's say you talk to someone in their mid-forties, they might be able to identify a handful of experiences from their childhood or teenage years that are very vivid, that they recollect very well. Turns out it may not be entirely their recollection. It may be the stories they heard about it from other family members and so on. So it's like some version of that reality, but it's not exactly the same thing as what actually happens. But if you ask them about other times in their life where there may have been specific things that are happening that are very, very vivid.

Maybe if it was the birth of a child or receiving a big award or the death of a family member, something very positive or very negative, something very emotional, they might have a lot of memories around that time that come back with a lot of clarity. They might call them, you know, the, I feel like this was just yesterday. And when they bring them back, they bring them with a lot of emotion. They're sort of reliving the experience. And we probably have a handful of those experiences in our past history, whether it was, you know,

something that happened to you or to your family member or something that happened around us, some crisis or an attack or something that is very natural disaster, something very salient. Once during a series of earthquakes, I hid under a table for two days and my mom would come and bring me hot dogs. Those memories typically are very, very strong and long lasting. But if you were to track, for example,

my memory for events that happened in my life, I have a lot of black holes. There are lots of periods where I just don't have the greatest recollection. But if somebody were to ask me about it and remind me and tell me stories about it, I can piece it back together. What's that all about?

So this is the tension between queued recall versus free recall. If there's a queue, if I see a picture, if I see a name, and that reminds me of something, I can bring that back with relative ease. And that tells me it's been stored. It's somewhere in my brain, but I needed to find the right queue to be able to bring it back. And I think that's a general experience that a cued recall of the past is much easier to trigger

than just asking somebody to freely recall. When they freely recall, you'll identify very quickly those black holes in their history. You know, you mentioned the birth of a child, which I was just talking to my mother-in-law about this the other day, about the amnesia that happens when you give birth. I have not had children, but from what I understand, I have heard that you immediately forget

that that was the most excruciating pain a human being can feel, and then you're like, let's do this again and have more babies. I imagine if that is true, there's definitely an evolutionary purpose for that, but is there something hormonal that just says don't worry about it? There must be. There must be some by a lot. I mean, I've heard the same exact thing. I can attest this is to be true.

You can ask my wife the same exact thing. And yeah, it's like, are you forgetting how painful that whole thing was? No, let's do it again. And you're right, there is something to that. And according to the papers, Memory for Labor Pain, a review of literature, labor pain intensity is remembered accurately or decreases on recall.

And researchers have suggested that the recall of childbirth, including recall of its pain, may be subject to what's called the halo effect. Since recall of negative aspects of childbirth, including severe pain, is incompatible with a positive experience of having a baby, memories are positively affected, at least in the short term. And that this hypothesis would predict that recall of pain would be reduced. So this is called the halo effect.

But it's a little more than just forgetting how much it hurt. It's not so much that the memory of the pain just evaporates, but it's that it's eclipsed, hopefully by the relief of having gone through it. And if all goes well, having a new creature exists, plus the boost of knowing that you coped and that you got through it. But some of those early days also can just be a little hazy. Now, we have to also not discount the fact that right after birth, there's a period of sleep deprivation, there's a period of you're sort of walking around really like a cognitively impaired patient for some time because of the sleep loss, the change in rhythms, that

constantly having to feed another human being, you being, all of those things are very, very difficult for the body to be able to adapt to and very difficult for the brain to be able to adapt to. So whether or not what you're experiencing during that period of time ends up being sort of not tracked, because our machinery that allows us to learn and encode and remember things is disrupted a bit, that may be the case, that may be a contributor to it. But I don't discount the possibility, again, that what you said is very interesting.

Maybe there's an evolutionary reason for this amnesia, especially surrounding perhaps the pain of the experience. And if some have had maybe a challenging pregnancy, they could perhaps forget about that and still wanna do it again. Yeah, there's a good survival evolutionary argument to be made around that. But I tend to make too many evolutionary arguments

and I can't ever substantiate them because we don't really know, right? So there's always the, we have no idea. It could have evolved this way. It totally makes sense. It's just kind of a just so story. But if you were listening and you're screaming, I forgot nothing, we see you too.

So a 2020 study in the Journal of Anxiety Disorders, hey, titled Traumatic Memories of Childbirth Relate to Maternal Postpartum Posttraumatic Stress Disorder found that after labor, some new birthing parents experience what's called CB-PTSD, or Childbirth Posttraumatic Stress Disorder. And they had muddier memories of the events of labor, but they also experienced more emotional and sensory details and had more involuntary flashbacks of it. And their childbirth experience was also a greater factor in their identity. And there was a 2023 study titled, Relationship Between Birth Memories and Recall and Perception of Traumatic Birth in Women in the Postpartum One-Year Period and Affecting Factors.

And that used data collected with something called the Birth Memories and Recall Questionnaire and Perception of Traumatic Childbirth Scale to find that nearly half of all the study participants who gave birth perceived the experience as traumatic, nearly half trauma. However, it offers that more birthing education before labor and support from medical personnel during and after labor can lessen the perception and the memory of the trauma. Do we know anything about, I mean, speaking of traumatic experiences, do we have any idea

why some things that are really negatively impactful, like remembering where you were if you were alive when the towers were hit? Or the moment that you heard COVID was a thing and that we were going into lockdown, or the insurrection of the United States Capitol, or that Betty White died. My mom used to talk about when she heard JFK was shot, where she was standing and what she was wearing versus, you know, with some childhood trauma, people have maybe subconscious recollections,

but nothing that they can piece together. Why do big events like that have different storage? We talked about this a little bit when we talked about flashbulb memories, right? And a lot of times those can be related to your own experiences, something very emotional, very salient, very consequential, deeply impacted or maybe threatened your survival, those kinds of things. We're going to have some vivid recollections about that.

I still remember very vividly when the Twin Towers got hit and the memories of that come back very quickly and the emotion with that comes back very, very quickly. And same thing, you know, when people talk about the JFK assassination, when they talk about other events that have happened, they say, I remember exactly where I was. I remember the conversation. I remember what I was wearing to this extreme level of detail. But there's a caveat. So psychologists used to always think of those as flashbulb memories. These are incredibly detailed kinds of recollections. No one ever questioned their veracity.

No one ever questioned whether they're actually accurate. Till people did the studies. And you determine very quickly when you look at this body of literature, looking at flash-bulb memories, and I'll give you an example in a second, that even though the confidence in those memories is extremely high and the emotional context is extremely high, the actual accuracy of the details sometimes can be quite low. What? Which was a surprise for a lot of people to hear.

And I'll give you an example. This was a study, I think, from the early 2000s by a colleague down in San Diego, Larry Squire. He looked at, now granted this is not as traumatic as some of the things that we talked about, but it was still a big news making event and it was the verdict in the O.J. Simpson case. October 3rd, 1995, a former football player and actor

was acquitted of killing his ex-wife Nicole Brown Simpson and her friend Ronald Goldman. And you may not have been born yet, but every TV seemed tuned to it. I was learning about plants in a classroom at the time. And yeah, my teacher had the TV on for it. And they asked people questions. These were college undergraduates, questions about this event, things like where were you

at the time? What did you hear? How did you hear it? What was the context? And then ask them again after a few months and then ask them again after a year. And they determined again very quickly that initially when you ask,

you get a lot of accurate details and very few sort of distortions or what we call illusory details. Illusory implies this false impression based on a faulty observation or one that's influenced by emotions. But as you wait a while and you ask that question again, you find that things flip. And actually the majority of the details that are brought back are now illusions or distortions. And the number of accurate things is actually quite low.

And this is consistent with what we know to be true in the false memory literature. Another colleague here, Beth Loftus, made a career of studying false memories. She's really one of the biggest pioneers in this area. She's always quick to point out how fallible our memory systems are. Just because something is highly emotional or highly traumatic does not automatically mean it's going to be stored with high fidelity. We tend to have a bit of a contrast that happens when a traumatic event is happening to us.

We focus on particular central features of that event that are really important for our survival. If somebody is held at gunpoint, for example, they might recall that gun, where it was pointing the color, details about that, but they may very, very quickly forget what the assailant was wearing or in some cases the race of the assailant. And it leads to all sorts of false eyewitness testimonies, it leads to a lot of these illusory memories or memory distortions that surface. And she's very good at demonstrating this in laboratory studies. So you can demonstrate very quickly that eyewitness testimony is subject to all sorts of leading questions that can change the way that these memories are stored in the brain.

You can quickly implant false memories into people's brains just by giving them false narratives and then they incorporate it. None of this is lying or malice, by the way. this is actually changing the stored memories. Now, this work is very, very, very tricky. And this neuroscientist, Beth Loftus, has come up against a lot of criticism, even death threats for research and data about how traumatic memories are stored and how evidence based on witness testimony can be flawed, which has led to the acquittal or exoneration of some alleged perpetrators of crime. So debatable memory is in fact very debatable and people do debate it.

And the difficult part about all of this is that there's so much we don't yet know about how the brain works. And I was thinking about this and in my 20s, I was held up at knife point and I was too frozen to scream. It was one of those, it was like a dream where you can't even make a noise, but I was still able to scream. It was one of those, it was like a dream where you can't even make a noise. But I was still able to memorize the license plate

of the getaway car. And then the detective came to my house and showed me photos to ID the suspect. And I was like, that's the guy. And I picked a guy who had a strong alibi and was not there. But the guys who stole my stuff ended up using my cell phone to call their girlfriends. So they got arrested.

And I felt bad because they were juveniles. They were like 17. But the guys who stole my stuff ended up using my cell phone to call their girlfriends, so they got arrested. And I felt bad because they were juveniles, they were like 17. And I think about that mugging all the time. And I feel like I still remember so many details really clearly, but I wonder how many have warped by now, which is terrifying.

But I think about those two kids a lot and just what they're doing now and how they're doing. I bet they don't remember me, and that's fine. And that goes back to teach us something very important about memory, which is that it's very dynamic. It's not static, it's not always the same. It is constantly dynamic and malleable and changing. And anytime that I hear something that's related

to something that I already know, what I already know changes a little bit to accommodate this new thing that I just heard. So our memories are constantly being corrupted. Anytime that I tell you about something from my childhood, you're going to get maybe like 30% accurate details and the rest of it is just fiction. How do we trust anything? Yeah, that's a challenge. I think that it starts to really question the value of the stories and the value of reminiscing,

the value of being able to tell. The key thing to remember is again, this is not what memory has evolved for. You still have the social thing when you tell stories, even if they're not true, you can still bond, you can tell very interesting stories, very interesting narratives. But the key thing to remember is that despite the fact that the details you remember may be different, your memory system and your brain have extracted whatever knowledge was necessary to be able to promote your survival successfully. Because that's what it evolved to do. That's what it got wired to do. It'll still do that regardless of what details you remember, what details

you're able to tell in the stories. What about memories that we don't remember by design? Do we remember things subconsciously? Do we remember, say, childhood traumas or things like that that are subconscious that we consciously don't want to pull up and envision? The idea of an unconscious memory that's stored that is very difficult to have come to the surface

has been talked about by psychologists and philosophers for a long time. We talk about repressed memories. I mean, you can get Freudian with this, right? But even if you look at whether or not this phenomenon happens, 100% it happens. It's real. You can see it in the clinic. You can see it as you talk to people.

And there are ways to be able to get that information to come out. The psychologist perspective would tell you that these memories may be so traumatic, so difficult to deal with, that having them come to the surface would essentially incapacitate the person so much that it's a survival tool to be able to store it in a way where it is not directly accessible. Now that's very uncomfortable talk to a neuroscientist. So every time that I've heard that, I sort of cringe a little bit and go, I don't know what mechanism that would be. And I still don't know the answer. So the unfortunate answer that I can give you, I guess, is I don't think this is very tractable for a neuroscientist to study. Now, certainly there are things that are beyond our consciousness

that can impact behavior. And we can do that in the laboratory. We can have a memory that is sort of taught to you over time in a laboratory setting that unconsciously changes how you behave in a certain task. That's easy to do, but that's different from repressed memories and trauma and those kinds of things. That's very difficult to study in a laboratory setting. So I have to sit with that discomfort for some time, but unfortunately the psychologist may be the only ones with some sort of answer for this one at this time. You know, you mentioned different senses helping you store a memory. The more senses maybe that are involved, perhaps the more vivid it becomes. Yes. But where does something like

synesthesia play a role where you maybe have different colors for dates or different emotions for sounds, things like that? Yes. So great. You started with the definition of synesthesia, and that's an important one to think about, right? Is that it's a form of sensory crossing. So things that normally should be seen and visualized may be heard,

and things that may be heard may have a certain color to them. And we hear these stories all the time. So the way that we used to think about our senses is that they operate in parallel and they're totally different from each other. However... You recognize, oh, actually, our sensory modalities cross all the time, and they talk to each other all the time, and they connect modalities cross all the time and they talk to each other all the time and they connect with each other all the time.

So a great example that I think V.S. Ramachandran does this example sometimes in his talk. One of them is Kiki, one of them is Buba. Where he'll draw two things on the screen, one little figure with very, very sharp edges and one with very soft rounded edges. Which one is Kiki and which one is Buba? How many of you think that's Kiki and that's Buba? Raise your hand.

And he'll say, if I tell you that one of these is called Kiki and the other one is called Buba, which one is Kiki, which one is Buba? Of course. It's very simple. Everyone says the rounded edge version is Buba, the sharp edge version is Kiki. And he would say, well, that tells you that you have a little bit of synesthesia. There's no reason why you might link the name with the shape this way unless there was some form of sensory crossing. So all of us have a little bit of that crossing. However, in documented cases of actual sensory crossing that is much more

dramatic where, let's say you're playing the piano and you hit a certain note and you see a certain color, maybe a warm red or something like that. That is a sort of a formal way to be able to look at that crossing. In many cases, it elicits creativity and it leads to a very interesting experience of the real world around you. Instead of having to kind of work at creating multimodal traces of the world, now everything seems to also be multimodal for you. So learning might be a little bit easier, you get all sorts of interesting talent that arises from that.

But I will go back to one case that I mentioned, and that was Alexander Luria's patients who had this perfect recall. What I didn't mention to you is that particular patient, he called him patient S, also had an extreme form of multisensory synesthesia. So again, having a sense linked to another sense, like associating flavors for different words. And apparently, Charlie XCX has synesthesia and has said, I see music in colors. I love music that's black, pink, purple or red, but I hate music that's green, yellow or brown," she says. Wait, so she hates green music? That's like her brand. So I looked into this and she told Vogue magazine that she chose that neon lime shade for her album art for

Bratt because, quote, I wanted to go with an offensive, off-trend shade of green to trigger the idea of something being wrong, she shared. Now me, your internet dad, I have synesthesia and for a long time I didn't know that it was weird for different years to be different colors or numbers to have personalities or songs to have different shades to them. And my friend Micah, who I'm about to mention again,

hi Micah, says that when he's mixing music, he's a musician, sharp notes taste like metal to him. All of this without the expense of hallucinogens. And it's impossible to be able to reproduce what that experience is like for someone who doesn't have it. I can't possibly know what that experience of the external world is, because I can only tell based on whatever it is that they describe. Now in his case, that seemed to help be able to have this perfect recall and be able to

retain things with a very, very high fidelity. But again, he was not a very well adjusted person. He struggled in social settings, struggled to maintain a job and all of those kinds of things. So a little bit of synesthesia seemed to work well. One or two senses being crossed for creativity seems to work well, but a dramatic sort of five-way synesthesia, which is what he had, that seems to be quite devastating. Do neurobiologists ever look to people who have either lost their sight or never had it or people who are hard of hearing or deaf to, or my friend Micah, I've talked about him, sorry Micah, lost his sense of smell as a baby when he had a fever and how maybe that lack of input from one sense changes the way we remember things?

Absolutely. And it goes back to the concept of plasticity. And we talked about this a little bit in the context of learning new things. But when it happens developmentally also, there's a massive capacity for rewiring. So when you look at individuals with congenital forms of blindness, let's say now they're an adult and you put them in an MRI scanner and now you're giving them an auditory stimulus. So this is an experience that they're hearing, they're listening. What you find in some cases is activity in their visual cortex.

Hmm. So areas of the brain associated with vision go off in a person who's blind. Which is really interesting because it suggests that this part of the brain has not been getting the appropriate input since birth, but it has adapted and become plastic to respond to input from other senses. And some have suggested that that might allow those senses to become much more sharply tuned and sort of much more accurate. And I'm not saying that, you know, for some humans, you have like bat-like echolocation and so on, but that has been claimed in some cases

of those with congenital blindness is that you get this increased sharpness of their other senses. But there is something to be said for use it or lose it. The cortex is there. And if the cortex can start to listen to other senses that are coming in and wire appropriately, it's going to try to be useful for them.

Is that sort of like using resources or real estate that you wouldn't otherwise be using or is that so off of an analogy? No, I think that's a great analogy. We talk about resources and real estate all the time because the cortex, I have a colleague here who has studied the cortex in brains of animals for a long time and he makes the claim, and I agree with this claim, that cortex is cortex throughout. And the same stuff that makes your visual cortex also makes your auditory cortex and also makes your other sensory cortices.

So one can sort of fill in for the other. The difference is, of course, the reason why they're all different from each other is by virtue of the inputs, the things that are coming in. But if that's changed, if that's altered, and they can sort of adapt and listen to other input, then they can be useful. And that's just using more resources, more real estate. In some ways, you can think of the brain as a very primitive object here, right? It's going to use whatever it has access to, whatever it can, to be able to solve challenges,

to be able to address questions and allow the organism to survive to the best of its ability. And if one way to do that is by rewiring and listening to a different form of input, why not? Mm-hmm. Oh, I have questions from listeners. Can I ask you one, William? Of course.

Yes. So ask neuroscientists your neurotic questions if you're me. And hoo boy, how many next week do we have a great part too with all your questions on how to remember names and faces, what causes dementia, photographic memories, amnesia, short-term memory, memory and executive function, so much more. So thank you to Dr. Michael Yasa and everyone down at Irvine for helping arrange this. More links to the lab and his work are in the show notes and up on our website at alliward.com slash ology slash nemanology. We are at ology on

Instagram and now blue sky where it seems everyone is headed. Hop in, water's warm, sky is blue. Also hello to everyone listening on Spotify I love to see your yearly wrapped lists and your comments for every episode. Smology is our shorter kid friendly episodes that you can find anywhere you get podcasts just look for the new green artwork by a Portland artist Bonnie Dutch who for the holidays or any occasion Bonnie Dutch can make you a wonderful custom pet portrait or other commission B.O.N.I. Dutch you can find her. Thank you to Erin Talbert

for adminning the Ologies podcast Facebook group. Avaleen Malik makes our professional transcripts. Kelly Ardwire does the website. Noelle Dilworth is our scheduling producer. Susan Hale, managing, directs it all. Jake Chafee edits and lead editor. And another great brain is Mercedes Maitland of Maitland Audio with some assists

from Jarrett Sleeper of Mindjam Media. When I am late on things and Mercedes and Jake have to go to bed I'm so sorry. I'm a little down to the wire because of the holidays but everyone's wonderful and thank you so much. Nick Thorburn wrote the theme music and if you stick around to the end of the episode I tell you a secret and this week is that I have an audiobook mixtape in the works and I wanted to have it up by Thanksgiving here in America but I chilled too hard on a farm for a few days for over the holiday. And we played this game that my friend, Katherine Burns, she is two-time Emmy award-winning choreographer, Katherine Burns, who I've known for decades. So she,

her favorite game to play is Catchphrase Jenga that she invented where you play Catchphrase, which is this little game that you can purchase. it looks like a frisbee with a little screen and it gives you phrases that you have to gather people to guess. You can also get it an app like it on your phone. So whoever is left holding the catchphrase when the timer goes off then has to withdraw a Jenga block. So it's just catchphrase but instead of points you just have to do Jenga. Honestly the stakes, the phrase guessing, it's a thrill. What a way to pass several hours at a time. I love it. Catchphrase Jenga. Get into it. Also that audiobook mixtape will be up in like a

day or two. Sorry. Great books from somatologist authors. It's like a scholastic catalog in your ears. But next week, more memory, part two. It's so good. Okay, bye-bye. Hacodermatology, homology, cryptozoology, lithology, nanotechnology, meteorology, nephrology, serology, selenology. Real is simply electrical signals interpreted by your brain.