Everyday Neuro 024: Mental Time Travel – How the Hippocampus Enables Recalling the Past and Imagining the Future

Introduction to Episode

0:00Hello, and welcome to the Everyday Neuro podcast series. I'm your host, Dr. Janine Cooper, and I'm aiming to provide you with the knowledge and inspiration to understand the fascinating world of the human brain. So hello, and welcome to another episode of the Everyday Neuro podcast. And I'm going to start by asking you a little bit of a strange question. Were you aware that your

0:35brain contains a time machine? Yep, you heard me correctly, a time machine. And perhaps for those of you who are familiar with the Time Lord Doctor Who, similar to their time machine, the TARDIS, that's much bigger on the inside than the outside. The brain's time machine is very small, but it has an incredible array of functions. So what part of the brain am I referring to? Well, as the title of this episode suggests, it's none other than my favourite structure, the hippocampus. The hippocampus

1:12has amazing abilities. It can help you remember past events and special moments. It also makes it possible to daydream about the future. And if that's not impressive enough, it's also your GPS, helping you navigate and imagine new places. You may recall that I first introduced you to the hippocampus early in the podcast series, and I dedicated episode eight to some of its functions. However, today, I wanted to revisit it to be able to honour the life and work of Professor Eleanor

1:45Maguire, a pioneering neuroscientist whose research studying the hippocampi of London taxi drivers has reshaped our understanding of the brain and autobiographical memory. Eleanor, as you will discover, was a fantastic researcher, and she was also a great influence on many people's lives who worked in the field of neuroimaging and memory. And I was fortunate to be one of those people. Keep your wellness routine going strong all summer. Cachava's new travel packs help you

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3:46Sadly, Eleanor passed away in January 2025, but has left us with a legacy of incredible work. And today I will share some of that work with you and also investigate how thanks to her team's research that focused on studying the brain region, the hippocampus. We now have a much greater understanding of our internal GPS that enables us to navigate in space. Also how we construct scenes and also the ability to time travel to recall our past personal experiences and also imagine our future.

Eleanor Maguire's Life

4:24So let's start today by finding out a little bit more about Eleanor McGuire. Eleanor McGuire was born in 1970 in Dublin, Ireland, and she studied psychology at University College Dublin, where she earned her bachelor's degree in 1990. And then she pursued a master's degree in clinical and experimental neuropsychology at the University of Wales in Swansea. And then she completed her PhD at the University College Dublin in 1994. Now, Eleanor was a professor

4:58of cognitive neuroscience at University College London, where I had the pleasure of working with her and also was a Wellcome Trust Principal Research Fellow. Her work has earned her numerous awards, including the prestigious LG Nobel Prize in 2003 and the Rosalind Franklin Award in 2008. So really quite the achievements. So now let's have a look at one of her most famous pieces of research, the London Taxi

5:31Driver Study, which resulted from her interest in understanding how the brain adapts to complex learning tasks. And she was particularly fascinated by the concept of neuroplasticity, which is the brain's ability to change and adapt in response to new experiences. So why did Eleanor choose to look at London taxi drivers? Well, that's because they undergo extensive training known as the knowledge and acquiring the knowledge to become a licensed black cab driver in London is a hugely rigorous process that

6:08typically takes three to four years and involves memorising thousands of streets, landmarks and routes within a six mile radius of Charing Cross. The process is intensive and requires a deep commitment to learning the intricate layout of the city of London. Studying taxi drivers who have acquired the knowledge using neuroimaging techniques called functional magnetic resonance imaging or fMRI provided

6:40Eleanor and her team with the unique opportunity to investigate how such rigorous training could physically alter the brain, specifically the hippocampus, which is now known to be involved in spatial navigation and memory. This research was groundbreaking at the time as it revealed that the hippocampi of taxi drivers was significantly larger compared to non-taxi drivers and it demonstrated that the brain's

7:11remarkable capacity for adaption and growth can happen through focused learning. So I'd like to now look at some of the changes that were observed in the hippocampi. Now, for those of you who are new to this podcast, many of the earlier episodes actually discuss the brain regions and tell you where they are and how you can sort of learn more about them. But what I would like to do is, as we're going to be talking about the hippocampi in this episode a lot, I'm going to quickly recap so that we can understand

7:45together the amazing results of Eleanor's studies. So we use the word hippocampi when we're referring to both sides of the brain. There is a hippocampus in the left side of the brain and a hippocampus on the right side. Now, if you were to stick your fingers in your ears and imagine them almost touching, that's where you'll find your hippocampi, right in the centre of the brain in the temporal lobe. Each hippocampus works together to help process and retrieve memories and, as you'll discover,

8:22navigate our environment. In Professor Eleanor Maguire's famous taxi driver's study, several significant changes were observed in their hippocampi. The taxi drivers had a larger amount or volume of grey matter, so brain cells in the mid-posterior hippocampus or the middle part towards the back of the structure. And this was different to non-taxi drivers. This area of the hippocampus

8:53is now known or thought to be associated with spatial navigation and memory. So if we lend ourselves to this idea, then those people that had studied the knowledge, those London taxi drivers, they've actually seen alterations to the size of their hippocampus in this mid-rear part. However, the taxi drivers had a smaller volume, so a smaller amount of grey matter, in the anterior hippocampus.

9:25So that basically means the front part, compared to the non-taxi drivers that were studied. This front part of the hippocampus is thought to be involved in encoding new experiences and memories. And what I mean by encoding is a bit like taking a photo with your phone. So when you see something you want to remember, you snap a picture. Well, your brain does something very, very similar by encoding the details of your experience, so you can then look at it, so to speak, in your mind's eye

9:58at a later time. The study also found a relationship or something we call a positive correlation between the number of years the London taxi drivers with the knowledge had been navigating the streets of London and the volume of their posterior hippocampus. These neuroimaging results suggest that the longer they had been driving, the larger this posterior or rear section of the hippocampus had become.

10:31And at the same time, there was this decrease in the volume or the sort of portion of the anterior hippocampus. And when I say anterior, remember I'm meaning the front part. This set of results, or data as we like to call it, had not been studied or seen before and it provided strong evidence of the concept of neuroplasticity, showing that the brain can adapt and change in response to the demands placed on it by specific tasks, such as extensive spatial

11:03navigation required by the London taxi drivers who had acquired the knowledge. However, if we think about the changes in the hippocampus that the London taxi drivers had shown, there might be a little bit of an expense of being able to encode other information. So this study has not only advanced our understanding of neuroplasticity, but it's also highlighted the profound impact that lifelong

11:35learning has on brain structure. And it really gives us new meaning to the adage, you're never too old to learn. As we now know that learning a new task not only positively equips our brain to remain healthy and active, but it's also fantastic for our well-being. So at any stage in life, learn something new. So these results have opened up new avenues for research into how we can harness neuroplasticity to be able to improve cognitive function and also treat neurological conditions. So I hope you found

12:12that interesting. And should you like to know a little bit more, then Eleanor's work has featured on a number of programmes, but I've provided you with a link to an Australian TV show called Catalyst that really looks at this in a little bit more detail. So Eleanor's contribution to neuroscience extend beyond the taxi driver study. And I'd like to now look at another function of the hippocampus

Scene Construction Theory

12:38with you, probably one of my favourite areas. It's the area of scene construction.

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13:50Scene construction theory is a concept proposed by Eleanor McGuire and her colleagues that suggests that the hippocampus is involved in constructing spatially coherent scenes. So basically, this is our ability to mentally construct a visual scene where the events happen in a logical order and the details are clear and easy to follow and the various parts of the scene will connect well together and make sense. I kind of like to think of it as a mental video or image clip that your brain has constructed

14:26from all of its stored memories and knowledge. Scene construction is essential for various cognitive functions and these include memory, imagination, and also our spatial navigation. So let's now together have a go at constructing a scene in your mind and turning the scene construction theory into real life. Because after all, a theory is only as good as the process it describes. So depending on where you are and what you're doing, as you listen to this episode, it will depend

15:00very much on how much you can take part right now. But for those of you who are actively doing a task, then perhaps you could try it later. If you can though, take a minute to consider going shopping for groceries. You might use your past memory to think about what shops you might go to, or usually go to, what foods or items you might want to buy by thinking what's in your cupboards, your pantry, and your fridge. You might also be visualising these items and shops in your mind. You may then think about how

15:33you will get to the shops and navigate your internal map in your mind using your brain's GPS to calculate the best route depending on the time of day and also the weather conditions. You might also think about the future and use your prospective memory to think about the best time to go that fits in with your schedule and plans. And also what meals you might cook or tasks you might complete once you have purchased the items. This grocery task seems simple enough to many people, but it's actually a complex

16:10process. So to recap, you've just used your retrospective past memory, including autobiographical memory of your past self. You have used your brain's navigational functions and your prospective memory to plan what you're going to do or what might occur. You've also had to factor in what is likely to happen in the real world compared to what could be fragments of your imagination. So perhaps you'll agree just how impressive this task actually is to accomplish. And by

16:44giving it a go, I hope it helps illustrate the key aspects of Eleanor Maguire's scene construction theory. And I'd like to now look at these aspects in a bit more detail. So as I've just described, spatial coherence is involved when the hippocampus helps create detailed and really good representations of scenes. This means that it can piece together different elements of a scene to form a complete and organized picture.

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17:50advertising on podcasts by visiting acast.com slash advertise. The theory also suggests that the same brain mechanisms used to remember our past experiences are also used when imagining future events or creating fictitional scenarios. So a little bit of make-believe. This overlap highlights the hippocampus's role in both recalling and constructing scenes.

18:21The theory also suggests that scene construction is crucial for us to be able to navigate as it allows individuals to visualize routes and landmarks. Now, I think my hippocampus from time to time doesn't always afford me this ability because my internal GPS is known for being a little bit off on most occasions. So anyway, I don't know about your hippocampi, whether they're working beautifully to guide you and navigate you, but this is definitely a role that Maguire and colleagues

18:57have said is really crucial. So this ability is particularly evident when we think about the results of the London Taxi Driver Study, who have highly developed hippocampi, especially in that mid-posterior area due to their extensive navigation experience. The scene construction theory, based on the results of Eleanor and team's studies, really emphasizes the notion of neuroplasticity. And as I mentioned earlier, the idea that the hippocampus can change and adapt based on new experiences and

19:30learning. And this neuroplasticity is evident in how the hippocampus can grow and reorganize itself in response to tasks that require intense spatial memory and scene construction. It was this theory that led me to study the work of Ellen Maguire as my PhD investigated delusions and confabulations of memory in people living with Alzheimer's disease. The scene construction theory was groundbreaking and it really helped me to get to grips with my research as it provided implications for understanding

20:06memory disorders such as Alzheimer's disease and amnesia. The scene construction theory also explains how damage to the hippocampus can affect the ability to recall and imagine scenes and in some people can potentially lead to scenes that are fictitious but are thought by that person to be real. Another reason I was so fascinated with Eleanor Maguire's research is that I wanted to develop ways to support memory issues that occur due to damage to the hippocampus, either due to an acquired brain

20:42injury such as dementia or a traumatic brain injury such as a fall or car accident that affects the hippocampus. The theory lends itself to cognitive rehabilitation strategies and it suggests that exercises aimed at enhancing scene construction abilities can actually improve memory and navigation skills in individuals with hippocampus. Overall scene construction theory provides a comprehensive framework for

21:14understanding the numerous roles of the hippocampus in memory, imagination and also spatial navigation. In 2005 I moved to London to work with an incredible team of people at the Institute of Child Health and we

Developmental Amnesia Study

21:30investigated developmental amnesia which I talk about in episode 8 along with the topic of autobiographical memory. It was during this time that I was fortunate to work with Eleanor and develop a study that looked at scene construction in a group of children with damage to their hippocampi due to developmental amnesia. The study investigated how damaged the areas of the brain that are associated with event memory in childhood, namely the hippocampi, impair the detailed recollection of personal memories about the self

22:04but not the ability to imagine fictitious events. Now this is in stark contrast to adults with similar damage who have impairment in both abilities. Now we were quite surprised at these results and we proposed reasons for such differences. Perhaps this has sparked a little bit of curiosity in you and should you like to read the article. We published it in 2011 in the journal Neuropsychologia and it's

22:35got a little bit of a long title so here we go. I'm going to take a deep breath. The effect of damage to the hippocampus in children on recalling the past and imagining new experiences and this was a wonderful experience for me in my research career because I got to work with some great people. They include Farineh Varga-Kidem, David Gadian and of course Professor Eleanor Maguire. So you can find this paper in the link that I'll provide in the show notes or you can even go into the research section of the

23:07Everyday Neuro website and have a look at it there. So that brings me to the end of this episode that is

Conclusion and Tribute

23:15dedicated to Professor Eleanor Maguire, an amazing neuroscientist and also a kind, funny and dedicated person who taught me along with many others about how to develop research that depicts real life abilities and also create research output whether it be an article, a workshop or a podcast episode so that it can be understood and enjoyed by a diverse audience. Speaking of audiences, your ideas for new topics are always welcome as are your thoughts and comments. Maybe you've come across

23:51some information that you'd like to share or even ask me a question. You can contact me either via the website or the Instagram account Everyday Neuro 2018. I'd really love to hear from you so please give me a message and it also really helps me to hear from you because then I can make episodes that feature your interests. So on that note, thanks again for listening and I hope you'll join me again for another episode of the Everyday Neuro podcast. Until next time, take care.

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