Mnemonology (MEMORY) Part 1 with Michael Yassa AI transcript and summary - episode of podcast Ologies with Alie Ward
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Episode: Mnemonology (MEMORY) Part 1 with Michael Yassa
Author: Alie Ward
Duration: 01:15:08
Episode Shownotes
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
Summary
In the first part of "Mnemonology (MEMORY)" with neurobiologist Dr. Michael Yassa, the complexities of memory formation, storage, and retrieval are examined. Yassa addresses common misconceptions, factors affecting memory, and emphasizes the brain's adaptability. He highlights the significance of the hippocampus, discusses the role of various brain regions, and debunks myths like the 10% brain usage fallacy. The conversation also touches on the dynamic nature of memory, influenced by emotions and neurobiology, setting the stage for further exploration of its implications on daily life and decision-making.
Go to PodExtra AI's episode page (Mnemonology (MEMORY) Part 1 with Michael Yassa) to play and view complete AI-processed content: summary, mindmap, topics, takeaways, transcript, keywords and highlights.
Full Transcript
00:00:00 Speaker_05
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.
00:00:07 Speaker_05
So this ologist 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.
00:00:21 Speaker_05
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.
00:00:32 Speaker_05
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.
00:00:48 Speaker_05
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 going to touch on that in a bit.
00:00:56 Speaker_05
But first, thank you to all the patrons who submitted questions for this episode, which we're going to cover wall to wall in part two next week. Because this is just a huge topic. There's so many good questions.
00:01:07 Speaker_05
Thank you to everyone getting Ologies merch from ologiesmerch.com. Thanks to everyone leaving us reviews, which boosts the show so much.
00:01:14 Speaker_05
And each week I remember to read them all, and I pick a 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 Ologies made the 10-hour days pass quickly. Lucy Goose-ay.
00:01:29 Speaker_05
I hope we saw a moose. And now onward. Okay, mnemonology 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.
00:01:41 Speaker_05
And that person's Google alerts, RIP, it's going to get screwed up because of this. But mnemonology is the study of memory.
00:01:50 Speaker_05
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.
00:01:58 Speaker_05
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,
00:02:14 Speaker_05
That thing where you can't remember a word. What memory is even for? How to let go of the past?
00:02:20 Speaker_05
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, pneumonologist, Dr. Michael Yassa.
00:02:55 Speaker_05
And I'm going to make you hold your mic a little bit like this. Dr. Mike, what do you prefer?
00:03:02 Speaker_02
Mike is perfectly fine. I am not very formal at all.
00:03:05 Speaker_05
I'll just call you Doc. How's that?
00:03:07 Speaker_02
I think anything aside from Mike would just make me feel very strange, but Doc is fine. Doc is fine.
00:03:12 Speaker_05
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 like what you do or will you just be diagnosing people without you?
00:03:25 Speaker_02
Oh my gosh. The question comes up like nonstop. The minute I say that I am 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.
00:03:37 Speaker_02
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.
00:03:46 Speaker_02
I'm like, yeah, tip of the tongue phenomenon. I try to tell them a little bit about how that works.
00:03:50 Speaker_05
We'll get to it.
00:03:51 Speaker_02
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.
00:04:03 Speaker_02
If I tell them I'm a professor, then I have to explain, well, you know, I do a little bit of teaching, but really I'm doing mostly research, right?
00:04:09 Speaker_02
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.
00:04:20 Speaker_02
Sometimes people will tell me about family members or will ask all sorts of interesting questions. And every now and then, something out of left field. I'll give you a great example.
00:04:28 Speaker_02
This is one of my favorites, and it's now come up several times when they ask 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.
00:04:41 Speaker_02
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.
00:04:46 Speaker_02
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.
00:04:53 Speaker_02
You know, they talk about like transplant cases, but you know, 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.
00:05:04 Speaker_02
So, that is where things live.
00:05:07 Speaker_05
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.
00:05:19 Speaker_05
And researchers call this clinical manifestations of body memories. In one 2021 study, insular cortex neurons encode and retrieve specific immune responses.
00:05:29 Speaker_05
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.
00:05:48 Speaker_05
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.
00:06:04 Speaker_05
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.
00:06:16 Speaker_05
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.
00:06:29 Speaker_02
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, you know, on a decline or anything like that.
00:06:40 Speaker_02
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.
00:06:50 Speaker_02
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.
00:07:01 Speaker_02
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.
00:07:10 Speaker_02
Of course, your brain doesn't actually stop thinking, but it surprises you sometimes when it comes up later.
00:07:15 Speaker_05
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 lithologica.
00:07:30 Speaker_05
According to this 2024 paper, coordinating words and sentences, detecting age-related changes in language production,
00:07:37 Speaker_05
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.
00:07:50 Speaker_05
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?
00:07:56 Speaker_02
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.
00:08:10 Speaker_02
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?
00:08:19 Speaker_02
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.
00:08:29 Speaker_02
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.
00:08:41 Speaker_05
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...
00:08:51 Speaker_05
And I can't, and I'm wondering in that moment if my brain is just like a bruised apple, just full of spots.
00:09:00 Speaker_02
That's a good one. I've never thought about a bruised apple analogy before. But you know, you mentioned as we get older, and I think that's part of it, but we're also busier and our sleep gets disrupted and all sorts of things.
00:09:12 Speaker_02
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.
00:09:21 Speaker_02
I think 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, right?
00:09:32 Speaker_02
But as we get older, our ability to be able to function and, you know, notwithstanding all of these distractions also is difficult, becomes more difficult.
00:09:40 Speaker_05
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 and our brains?
00:09:50 Speaker_05
Or is it so frustrating because it changes based on like the TikTok algorithm?
00:09:56 Speaker_02
So, when I first started to get interested in neuroscience, it wasn't clear to me how quickly our knowledge would change.
00:10:06 Speaker_02
Now, of course, when I teach students in undergraduate courses, I always tell them, look, I'm going to tell you, you know, 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.
00:10:20 Speaker_02
So what I tell you is likely going to 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.
00:10:31 Speaker_02
And that continues, and it actually continues at a very rapid clip. So I've been doing this for almost a quarter century now.
00:10:40 Speaker_02
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.
00:10:50 Speaker_02
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.
00:11:05 Speaker_02
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.
00:11:16 Speaker_02
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.
00:11:23 Speaker_02
So if you ask me what I think is going to happen in the next five years of neuroscience, I have no idea. The sky's the limit.
00:11:28 Speaker_05
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.
00:11:44 Speaker_05
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?
00:11:58 Speaker_05
How did you become someone who wanted to research the brain using your brain?
00:12:02 Speaker_02
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.
00:12:14 Speaker_02
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?
00:12:26 Speaker_02
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.
00:12:40 Speaker_02
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.
00:12:52 Speaker_02
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.
00:13:03 Speaker_03
The Matrix is the world that has been pulled over your eyes to blind you from the truth.
00:13:07 Speaker_02
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.
00:13:23 Speaker_02
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.
00:13:30 Speaker_02
Now that requires that you understand the brain at a fundamental level so well that you can fool it into believing this is a, you know, a reality.
00:13:38 Speaker_02
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?
00:13:46 Speaker_02
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.
00:13:55 Speaker_02
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.
00:14:10 Speaker_02
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 know, you have a pump in the heart, right? You have a filter in the kidneys.
00:14:21 Speaker_05
And yes, we just put out an episode about veins and arteries, and also we have one about kidneys and pee.
00:14:28 Speaker_05
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.
00:14:41 Speaker_02
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.
00:14:52 Speaker_02
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.
00:15:03 Speaker_02
So, shifted gears, didn't want to go to med school anymore.
00:15:06 Speaker_02
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, you know, however many decades without really getting to an end point.
00:15:18 Speaker_02
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.
00:15:29 Speaker_02
And now, 25 years later, I can say we know a lot more, but it still remains a small fraction of what we stand to know.
00:15:37 Speaker_05
When you were studying neuroscience and you were studying how memory works, did you have any hacks to remember what you were learning?
00:15:47 Speaker_02
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.
00:16:01 Speaker_05
I gotta do that episode.
00:16:03 Speaker_02
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.
00:16:13 Speaker_02
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, certainly in the context of diseases, that's important.
00:16:24 Speaker_02
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.
00:16:34 Speaker_02
So when I teach students about this, I tell them this is my no cramming rule.
00:16:39 Speaker_02
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.
00:16:53 Speaker_02
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.
00:17:03 Speaker_02
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.
00:17:17 Speaker_02
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.
00:17:25 Speaker_05
Yes, rest is important for remembering stuff.
00:17:29 Speaker_02
So the more that you interspace your study sessions and you have 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.
00:17:40 Speaker_02
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 an auditory learner or a kinesthetic learner,
00:17:53 Speaker_02
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.
00:18:05 Speaker_02
The reality is if you do the right experiments, you'll uncover the fact that there's no such thing as a learning style.
00:18:11 Speaker_02
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.
00:18:28 Speaker_05
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
00:18:48 Speaker_05
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 squeaky about that, including Gardner himself.
00:19:04 Speaker_05
So while the notion of learning styles are a myth, engaging more senses can help with recall.
00:19:11 Speaker_02
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.
00:19:22 Speaker_02
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, you know, brain imaging and so on to tell us all that.
00:19:33 Speaker_02
We just knew it simply from practice and behavior. So that's another really fun one that I realized early on.
00:19:40 Speaker_05
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.
00:19:55 Speaker_05
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.
00:20:09 Speaker_05
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.
00:20:25 Speaker_05
It's very slippery looking. But what parts of our brains are we filing it and how does it stick?
00:20:32 Speaker_02
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 a one-size-fits-all.
00:20:43 Speaker_02
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.
00:20:53 Speaker_02
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, and that tends to get stored in some systems in the brain, typically not the hippocampus, actually.
00:21:05 Speaker_02
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.
00:21:16 Speaker_02
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.
00:21:26 Speaker_02
So that memories 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?
00:21:35 Speaker_02
I ask the counter question, which is, where does it not get stored? It's sort of everywhere.
00:21:39 Speaker_02
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.
00:21:58 Speaker_05
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.
00:22:12 Speaker_05
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 like occipital lobe or the temporal lobe or
00:22:24 Speaker_02
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.
00:22:38 Speaker_02
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.
00:22:47 Speaker_02
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.
00:22:58 Speaker_01
It's all over the place.
00:23:00 Speaker_02
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.
00:23:08 Speaker_02
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.
00:23:16 Speaker_02
So it creates and holds on to 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.
00:23:26 Speaker_02
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.
00:23:38 Speaker_05
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.
00:23:52 Speaker_05
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.
00:24:05 Speaker_05
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.
00:24:21 Speaker_05
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.
00:24:34 Speaker_05
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.
00:24:47 Speaker_05
We used to think that glial cells were just kind of like hung out near nerve cells like wingmen. 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.
00:25:01 Speaker_05
Microglia are the brain's immune cells. Macroglia, like astrocytes, help modulate the levels of neurotransmitters around those synapses.
00:25:10 Speaker_05
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?
00:25:27 Speaker_05
Does science know yet what's firing off?
00:25:30 Speaker_02
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.
00:25:41 Speaker_02
So we have some ideas, we have some thoughts, and the ideas have been corroborated for many years now.
00:25:45 Speaker_02
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.
00:25:59 Speaker_02
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.
00:26:09 Speaker_02
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.
00:26:21 Speaker_02
If the cells learn something new, you can change the strength of that connection, you can change the firing rates, you can change whether or not that cell is able to trigger the other cell that it's communicating with.
00:26:33 Speaker_05
So how strong that ability is to toss a signal from one axon terminal to the branching fingery dendrites of the next cell.
00:26:42 Speaker_05
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.
00:26:55 Speaker_02
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.
00:27:06 Speaker_02
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.
00:27:14 Speaker_02
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.
00:27:26 Speaker_02
You can guess as to where 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.
00:27:36 Speaker_05
So those neurons, the ones with the dendrites on one end, the long, trunky 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.
00:27:53 Speaker_05
Now, I crunched some numbers. Let's say the average haystack is five feet by six feet, and it weighs 1,700 pounds.
00:28:01 Speaker_05
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.
00:28:19 Speaker_02
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.
00:28:29 Speaker_02
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.
00:28:42 Speaker_02
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.
00:28:50 Speaker_02
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.
00:29:02 Speaker_02
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.
00:29:15 Speaker_02
Maybe 5, 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.
00:29:22 Speaker_05
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?
00:29:28 Speaker_02
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, ah, come on. You've got access. If you only had access to five to 10% of your brain, guess what?
00:29:42 Speaker_02
Only five to 10% of your brain would actually survive. The rest of it would just atrophy and go away.
00:29:47 Speaker_05
You're done with it, right?
00:29:48 Speaker_02
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 re-watching Lucy the other day. Oh no, why? There's a few of those terrible, terrible movies.
00:30:00 Speaker_02
Why did you do that? I know, it was just on TV. I couldn't help it.
00:30:03 Speaker_01
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.
00:30:16 Speaker_02
There's a number of these, you know, Hollywood blockbusters out there, whether it's, you know, you take a pill or some drug that like unlocks the full potential of the human brain.
00:30:24 Speaker_02
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.
00:30:30 Speaker_02
But the idea that you're kind of stuck using 5 to 10% and if you could just unlock like 90% you'd be this superhuman entity, no. We use all of our brain all the time.
00:30:44 Speaker_02
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.
00:30:56 Speaker_02
It's just kind of noise that sits there. But they have to be active in some respect, otherwise they wouldn't be useful.
00:31:02 Speaker_05
And you know, you said something about superhuman strength, but I know that there are some people whose memories are just bonkers, super, what is it, hyper... Highly superior autobiographical memory.
00:31:16 Speaker_05
The fact that that was on the tip of my tongue was just like putting on an MRI.
00:31:20 Speaker_02
Well, I'm glad you asked. So I happen to know something about those folks because we study them at UC Irvine.
00:31:27 Speaker_02
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.
00:31:34 Speaker_05
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.
00:31:49 Speaker_05
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.
00:31:58 Speaker_02
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.
00:32:09 Speaker_02
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.
00:32:19 Speaker_02
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 him the exact dates.
00:32:27 Speaker_02
And 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.
00:32:34 Speaker_02
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?
00:32:44 Speaker_02
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.
00:33:02 Speaker_02
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.
00:33:12 Speaker_05
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.
00:33:24 Speaker_02
And there were stories that were told. Alexander Luria, a famous psychologist, talked about one of his patients who had perfect recall. You would think that this person would be very sort of well adjusted, but he wasn't.
00:33:37 Speaker_02
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 a desirable. It was almost as bad as having a very poor memory. It was extreme.
00:33:50 Speaker_05
So according to the paper, The Mind of a Mnemonist, this subject in Alexander Luria's study was able to recall autobiographical information since one year of age.
00:34:00 Speaker_05
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.
00:34:09 Speaker_05
But he also experienced a type of crossing of the senses, which we're going to get to later in this episode.
00:34:15 Speaker_02
And the first thought as a scientist is you go, wow, that's unexpected. This shouldn't have happened, right?
00:34:22 Speaker_02
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.
00:34:35 Speaker_02
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.
00:34:45 Speaker_02
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.
00:34:54 Speaker_02
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.
00:35:03 Speaker_02
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?
00:35:14 Speaker_02
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.
00:35:24 Speaker_05
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.
00:35:36 Speaker_05
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.
00:35:47 Speaker_05
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.
00:35:59 Speaker_05
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.
00:36:04 Speaker_05
And this week, Mike asked that his donation, as well as his honorarium, go to his lab's fund to help graduate students.
00:36:10 Speaker_05
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.
00:36:21 Speaker_05
Now, find out more at the link in the show notes, and thank you to sponsors of this show for making that gift possible.
00:36:27 Speaker_05
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?
00:36:42 Speaker_02
So what happens to the average person if you're talking about the role of neurotransmitters in, say, memory storage? The way that we think about communication across brain cells is it's a combination of electrical and chemical communication.
00:36:57 Speaker_02
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.
00:37:09 Speaker_05
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.
00:37:20 Speaker_05
And those toss that electrical signal to the next dendrites, kind of like a daisy chain.
00:37:25 Speaker_02
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.
00:37:33 Speaker_02
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.
00:37:42 Speaker_02
So you have kind of electrical really fast, chemical a little bit slower, electrical again really fast, and so on.
00:37:48 Speaker_02
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.
00:38:03 Speaker_05
Now, neuronerds 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?
00:38:15 Speaker_05
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.
00:38:28 Speaker_05
But other said that it's the yolky cell guts on the dendrite or the dendrite branches themselves that are signaling the amount of neurotransmitter released. We need answers here.
00:38:39 Speaker_02
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.
00:38:49 Speaker_02
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.
00:39:01 Speaker_05
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.
00:39:12 Speaker_05
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?
00:39:23 Speaker_02
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.
00:39:36 Speaker_02
It is not necessarily the thing that makes memory happen.
00:39:40 Speaker_02
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 that 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.
00:39:59 Speaker_02
But in the last couple of years things changed a little bit. Dopamine started to become even more interesting.
00:40:03 Speaker_02
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 and its ability to store memories. And it turns out that some types of memories seem to be dependent.
00:40:17 Speaker_02
on dopamine rather than just modulated by dopamine. So 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.
00:40:30 Speaker_02
If you look at the textbooks, what is the role of dopamine? Very stereotyped answer.
00:40:35 Speaker_02
You're very much linked to reward learning, feedback-driven learning, but the data that's been accumulated since, and is maybe not in the textbooks yet, is there's these additional roles for dopamine that are just now beginning to be understood.
00:40:47 Speaker_05
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?
00:40:57 Speaker_05
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
00:41:17 Speaker_05
And hormones, the endocrine system, the HPA axis, all that plays a role in neurotransmitters, right? Does that mean that hormones play a role in our memory a lot?
00:41:27 Speaker_02
Absolutely. Especially when you think about the HPA axis.
00:41:31 Speaker_02
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.
00:41:51 Speaker_02
Because stress is one of those things where some of it is positive, too much of it is obviously very negative.
00:41:57 Speaker_05
For more on what's called eustress, we have a whole episode about happiness with Dr. Laurie Santos, or we have one on burnout with Dr. Candy Weens. So good and bad stress, your brain begs you to know the difference.
00:42:09 Speaker_02
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.
00:42:22 Speaker_02
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.
00:42:32 Speaker_05
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.
00:42:43 Speaker_05
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 or I always could remember my hotel rooms when I would travel.
00:42:53 Speaker_05
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.
00:43:02 Speaker_02
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.
00:43:16 Speaker_02
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.
00:43:26 Speaker_02
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.
00:43:38 Speaker_02
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 sort of to deal with this complexity, but it's a very cheap excuse, right?
00:43:51 Speaker_02
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.
00:44:07 Speaker_02
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 different levels that need to be studied as well.
00:44:15 Speaker_02
So this is about doing better science, more rigorous science, broadly.
00:44:18 Speaker_05
And this matters because many studies have shown that women and people assigned female at birth are actually humans who exist.
00:44:27 Speaker_05
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?
00:44:38 Speaker_02
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.
00:44:49 Speaker_02
But even if you study people in their 60s and 70s, there are really interesting individual differences in levels of estrogen at that stage.
00:44:57 Speaker_02
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.
00:45:07 Speaker_02
And even just if you're curious about the science, really interesting findings that are surfacing.
00:45:11 Speaker_05
Well, in the last 300,000 years, did we just not really evolve to be this old? Like, where does memory and evolution play a part? And age? I mean, some people say that they can remember their birth.
00:45:26 Speaker_05
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?
00:45:33 Speaker_02
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.
00:45:44 Speaker_02
You just named a couple of examples, even remembering birth. Now, I don't know that anybody can actually remember that. But, you know, certainly people claim to have very strong memories, even from an early age.
00:45:54 Speaker_02
In reality, your brain systems are still wiring up during development, so a lot of times those memories don't get held on to.
00:46:00 Speaker_02
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?
00:46:10 Speaker_02
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.
00:46:27 Speaker_05
Wait, so memory is not for thinking about the past? Huh.
00:46:32 Speaker_02
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.
00:46:45 Speaker_02
So it's all about survival. And if you think about it from that context of the 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,
00:47:03 Speaker_02
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?
00:47:15 Speaker_02
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.
00:47:24 Speaker_05
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.
00:47:37 Speaker_02
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.
00:47:50 Speaker_02
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.
00:47:59 Speaker_02
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.
00:48:14 Speaker_02
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.
00:48:22 Speaker_02
That seems to be protective, almost as much as physical activity, for example.
00:48:26 Speaker_05
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?
00:48:37 Speaker_02
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.
00:48:47 Speaker_02
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-40s.
00:49:01 Speaker_02
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.
00:49:08 Speaker_02
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.
00:49:20 Speaker_02
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,
00:49:35 Speaker_02
They might have a lot of memories around that time that come back with a lot of clarity. They might call them, you know, I feel like this was just yesterday. And when they bring them back, they bring them with a lot of emotion.
00:49:45 Speaker_02
They're sort of reliving the experience.
00:49:48 Speaker_02
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 some crisis or an attack or something that is very, a natural disaster or something very salient.
00:50:02 Speaker_05
Once during a series of earthquakes, I hid under a table for two days and my mom would come and bring me hot dogs.
00:50:08 Speaker_02
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.
00:50:17 Speaker_02
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?
00:50:27 Speaker_02
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.
00:50:39 Speaker_02
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.
00:50:45 Speaker_02
And I think that's a general experience, that acute 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.
00:50:58 Speaker_05
You know, you mentioned the birth of a child, which I was just talking to my mother-in-law about this the other day. the amnesia that happens when you give birth.
00:51:07 Speaker_05
I have not had children, but from what I understand, I have heard that's like, 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.
00:51:18 Speaker_05
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?
00:51:25 Speaker_02
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. Yeah, it's like, are you forgetting how painful that whole thing was? No, let's do it again.
00:51:40 Speaker_02
And you're right, there is something to that.
00:51:43 Speaker_05
According to the paper's Memory for Labor Pain, a review of the literature, labor pain intensity is remembered accurately or decreases on recall.
00:51:52 Speaker_05
And researchers have suggested that the recall of childbirth, including recall of its pain, may be subject to what's called the halo effect.
00:52:01 Speaker_05
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.
00:52:18 Speaker_05
So, this is called the halo effect. But it's a little more than just forgetting how much it hurt.
00:52:25 Speaker_05
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 exist, plus the boost of knowing that you coped and that you got through it.
00:52:41 Speaker_05
But some of those early days also can just be a little hazy.
00:52:44 Speaker_02
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 know, 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.
00:53:09 Speaker_02
So, whether or not what you're experiencing during that period of time ends up being sort of not tracked, right? Because our machinery that allows us to learn and encode and remember things is disrupted a bit. That may be the case.
00:53:22 Speaker_02
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
00:53:33 Speaker_02
perhaps the pain of the experience, and if some have had maybe a challenging pregnancy, they could perhaps forget about that and still want to do it again.
00:53:41 Speaker_02
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.
00:53:54 Speaker_02
It could have evolved this way. It totally makes sense. It's just kind of a just-so story.
00:53:58 Speaker_05
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.
00:54:12 Speaker_05
found that after labor, some new birthing parents experienced what's called CB-PTSD or childbirth post-traumatic stress disorder.
00:54:22 Speaker_05
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.
00:54:38 Speaker_05
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
00:54:51 Speaker_05
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.
00:55:08 Speaker_05
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.
00:55:20 Speaker_05
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?
00:55:34 Speaker_05
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.
00:55:43 Speaker_05
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.
00:55:57 Speaker_05
Why do big events like that have different storage?
00:56:02 Speaker_02
We talked about this a little bit when we talked about flashbulb memories, right?
00:56:05 Speaker_02
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.
00:56:15 Speaker_02
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.
00:56:27 Speaker_02
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.
00:56:39 Speaker_02
But there's a caveat. So psychologists used to always think of those as flashbulb memories. These are incredibly detailed kinds of recollections. And no one ever questioned their veracity. No one ever questioned whether they're actually accurate.
00:56:52 Speaker_02
till people did the studies.
00:56:54 Speaker_02
And you determine very quickly when you look at this body of literature, looking at flashbulb 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,
00:57:10 Speaker_02
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.
00:57:25 Speaker_02
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 newsmaking event and it was the verdict in the O.J. Simpson case.
00:57:35 Speaker_05
Mm-hmm. 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.
00:57:51 Speaker_05
I was learning about plants in a classroom at the time. And yeah, my teacher had had the TV on for it.
00:57:56 Speaker_02
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?
00:58:06 Speaker_02
And then asked them again after a few months, and then asked them again after a year.
00:58:10 Speaker_02
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.
00:58:20 Speaker_05
Illusory implies this false impression based on a faulty observation or one that's influenced by emotions.
00:58:28 Speaker_02
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.
00:58:42 Speaker_02
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.
00:58:53 Speaker_02
And she's always quick to point out how fallible our memory systems are. And just because something is highly emotional or highly traumatic does not automatically mean it's going to be stored with high fidelity.
00:59:06 Speaker_02
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.
00:59:18 Speaker_02
If somebody's 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.
00:59:32 Speaker_02
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.
00:59:43 Speaker_02
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.
00:59:52 Speaker_02
You can quickly implant false memories into people's brains just by giving them these false narratives and then they incorporate it. And none of this is lying or malice, by the way. This is actually changing the stored memories.
01:00:04 Speaker_05
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.
01:00:25 Speaker_05
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.
01:00:37 Speaker_05
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 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.
01:00:50 Speaker_05
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.
01:01:00 Speaker_05
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 or 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
01:01:23 Speaker_02
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.
01:01:34 Speaker_02
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.
01:01:46 Speaker_02
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.
01:01:53 Speaker_04
How do we trust anything?
01:01:57 Speaker_02
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.
01:02:11 Speaker_02
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.
01:02:19 Speaker_02
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.
01:02:31 Speaker_02
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.
01:02:39 Speaker_05
What about memories that we don't remember by design? Do we remember things subconsciously? Like, do we remember, say, childhood traumas or things like that that are subconscious that we consciously don't want to pull up and envision?
01:02:54 Speaker_02
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.
01:03:07 Speaker_02
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
01:03:16 Speaker_02
talk to people, and there are ways to be able to get that information to come out, the psychologist's 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.
01:03:31 Speaker_02
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.
01:03:41 Speaker_02
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.
01:03:49 Speaker_02
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.
01:03:56 Speaker_02
Now certainly there are things that are beyond our consciousness that can impact behavior and we can do that in the laboratory.
01:04:03 Speaker_02
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.
01:04:18 Speaker_02
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.
01:04:29 Speaker_05
You know, you mentioned different senses helping you store a memory. senses maybe that are involved perhaps the more vivid it becomes. Yes.
01:04:39 Speaker_05
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?
01:04:50 Speaker_02
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.
01:04:59 Speaker_02
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.
01:05:12 Speaker_02
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...
01:05:19 Speaker_02
You recognize, oh, actually, our sensory 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.
01:05:32 Speaker_02
Ramachandran does this example sometimes in his talks, where he'll draw two things on the screen, one little figure with very, very sharp edges, and one with very soft rounded edges.
01:05:44 Speaker_00
Which one is Kiki and which one is Bubba? How many of you think that's Kiki and that's Bubba? Raise your hand.
01:05:48 Speaker_02
And he'll say, if I tell you that one of these is called Kiki and the other one is called Bubba, which one is Kiki and which one is Bubba? Of course. It's very simple.
01:05:57 Speaker_02
Everyone says the rounded edge version is Bubba, the sharp edge version is Kiki, and he would say, well that tells you that you have a little bit of synesthesia.
01:06:05 Speaker_02
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.
01:06:14 Speaker_02
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.
01:06:28 Speaker_02
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.
01:06:39 Speaker_02
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.
01:06:52 Speaker_02
But I will go back to one case that I mentioned, and that was Alexander Luria's patient, who had this perfect recall.
01:06:59 Speaker_02
What I didn't mention to you is that particular patient, he called him patient S, also had an extreme form of multisensory synesthesia.
01:07:08 Speaker_05
So again, having a sense linked to another sense, like associating flavors for different words. And apparently, Charli XCX has synesthesia and has said, I see music in colors.
01:07:21 Speaker_05
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.
01:07:33 Speaker_05
So I looked into this and she told Vogue magazine that she chose that neon lime shade for her album art for Brat because, quote, I wanted to go with an offensive off-trend shade of green to trigger the idea of something being wrong, she shared.
01:07:49 Speaker_05
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.
01:08:03 Speaker_05
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.
01:08:16 Speaker_02
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.
01:08:30 Speaker_02
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.
01:08:41 Speaker_02
He struggled in social settings, struggled to maintain a job, and all of those kinds of things. A little bit of synesthesia seemed to work well.
01:08:50 Speaker_02
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.
01:09:01 Speaker_05
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?
01:09:25 Speaker_02
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.
01:09:38 Speaker_02
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.
01:09:51 Speaker_02
What you find in some cases is activity in their visual cortex.
01:09:57 Speaker_05
So areas of the brain associated with vision go off in a person who's blind.
01:10:02 Speaker_02
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.
01:10:14 Speaker_02
And some have suggested that that might allow those senses to become much more sharply tuned and sort of much more accurate.
01:10:22 Speaker_02
And I'm not saying that for some humans you have 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.
01:10:34 Speaker_02
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 that.
01:10:47 Speaker_05
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?
01:10:54 Speaker_02
No, I think that's a great analogy. I mean, we talk about resources and real estate all the time because the cortex, you know, I have a colleague here who has studied the cortex in brains of animals for a long time.
01:11:06 Speaker_02
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.
01:11:20 Speaker_02
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.
01:11:28 Speaker_02
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
01:11:41 Speaker_02
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.
01:11:54 Speaker_02
And if one way to do that is by rewiring and listening to a different form of input, why not?
01:12:00 Speaker_05
I have questions from listeners. Can I ask you one, William? Of course.
01:12:02 Speaker_03
Yes.
01:12:06 Speaker_05
So ask neuroscientists your neurotic questions, if you're me. And hoo boy, howdy. Next week, do we have a great part two.
01:12:14 Speaker_05
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.
01:12:25 Speaker_05
So thank you to Dr. Michael Yassa and everyone down in Irvine for helping arrange this. More links to the lab and his work are in the show notes and up on our website at alleyward.com slash ology slash pneumonology.
01:12:36 Speaker_05
We are at ologies on Instagram and now blue sky where it seems everyone is headed. Hop in, water's warm, Sky's Blue. Also, hello to everyone listening on Spotify. I love to see your yearly wrapped lists and your comments for every episode.
01:12:50 Speaker_05
Smologies are shorter, kid-friendly episodes that you can find anywhere you get podcasts.
01:12:53 Speaker_05
Just look for the new green artwork by 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.
01:13:06 Speaker_05
Thank you to Aaron Talbert for adminning the Ologies podcast Facebook group. Aveline Malik makes our professional transcripts. Kelly Ardwire does the website. Noelle Dilworth is our scheduling producer. Susan Hale managing directs it all.
01:13:16 Speaker_05
Jake Chafee edits and lead editor. And another great brain is Mercedes Maitland of Maitland Audio with some assists from Jarrett Sleeper of MindGem Media. When I am late on things and Mercedes and Jake have to go to bed, I'm so sorry.
01:13:28 Speaker_05
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.
01:13:36 Speaker_05
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.
01:13:46 Speaker_05
And we played this game that my friend, Catherine Burns, she is two-time Emmy Award-winning choreographer, Catherine Burns, who I've known for decades.
01:13:55 Speaker_05
So her favorite game to play is catchphrase Jenga that she invented where you play catchphrase, which is this little game that you can purchase.
01:14:04 Speaker_05
It looks like a Frisbee with a little screen and it gives you phrases that you have to get other people to guess. You can also get an app like it on your phone.
01:14:12 Speaker_05
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.
01:14:27 Speaker_05
What a way to pass several hours at a time. I love it. Catchphrase Janka. Get into it. Also, that audiobook mixtape will be up in like a day or two. Sorry. Great books from somnologist authors. It's like a scholastic catalog in your ears.
01:14:42 Speaker_05
But next week, more memory part two. It's so good. Okay, bye-bye.
01:15:04 Speaker_01
and real is simply electrical signals interpreted by your brain.