Many speakers have stood in this theatre over the years
contemplating the nature of the universe.
Whether time travel is possible, could we build a time machine?
As a nation, we adore our science fiction time lords and the star trekkers who can transport themselves
at a flick of a switch through space onto alien worlds.
But the reality is that we already have a device
that can do all of those things and more
a teleportation machine that can effortlessly transport us to different times and different places
I'm talking, of course, about the brain. The universe within.
In this discourse I am going to consider why and how the brain allows us to accomplish this wondrous feats.
And the answers in fact come from an understanding of memory.
We're endlessly fascinated by memory, we desire to improve it, we fear its loss.
As this quote illustrates quite nicely I think,
But the importance of memory goes beyond the individual and their personal autobiography.
We share memories and in many ways memories are the glue that holds society together. They're the basis of culture.
If you think about it, if we didn't have memory, we would constantly keep reinventing the wheel
and there would be an awful lot of 'ground hog' days.
Well I'm going to show you that memory is not just one thing. It also doesn't just occur in a vacuum.
It's not even that accurate and in fact it's not really about the past
Scurrilous notions you might think but I'll argue that these features are in fact the key to our ability to mentally travel through space and time.
So let me illustrate.
There are many different types of memory, it's not a unitary phenomenon.
So we have short term memory and this is for information that we need to hold on to or rehearse for immediate use.
Now the example I've given here is phone numbers but I realize now, actually, that in a sort of perverse reversal
that in fact our phones have actually become our short term memories.
But we also have long term memories and one sort of long term memory is skills or habits.
So we learn to ride a bicycle and then it becomes automatic, we can do it effortlessly, probably for life.
And then there are these other types of memories, the rich, personal memories that punctuate our lives.
And these are known as episodic or autobiographical memories.
Now we know there are these different types of memories because damage to different parts of the brain impact selectively on these memory types.
So for example, in a classic amnesia, which I'll talk more about later, patients cannot form new memories
and they often lose the memories of their past experiences.
But despite what the Hollywood movies would have us believe they do remember who they are.
They do remember who their families are and they remember facts about the world.
It's this selective loss of autobiographical memories that they have.
By contrast, there's a certain type of dementia  where the first thing that's compromised is this sort of memory.
The memory for facts about the world, concepts, their vocabulary, their naming ability.
But their autobiographical memories, at least in the early stages of the disease, is intact.
So memory comes in different forms, supported by different brain areas and of course they all interact.
Now another important feature of memory is illustrated by an experiment from over forty years ago
but it still makes the point in a very compelling way.
Now the experiment would take too long to do here but let me just give you a sort of sense of it.
So it involved text such as this.
And subjects had to memorize this text, so let me read quickly through it.
*reads text on screen*
So there is the subject, faced with this piece of text, had to memorize it.
Tricky I think you'll agree because it doesn't really make much sense.
They saw this scene.
And then they memorized the text.
And the subject who saw this scene very briefly did much better on the memory test than those who weren't exposed to the scene.
So memory works better if it occurs in a context.
If we can draw upon our prior knowledge about how the world works and link the incoming information with what we already know.
Now testing memory also consistently reveals something else of importance.
Now I would be failing in my duties as a memory researcher if I didn't take the opportunity to test your memories.
Okay.
So, let's get down to business.
You're going to see a countdown of three... two... one...
Then you're going to see a picture flashed on the screen very briefly so you've got to pay attention.
There'll be a brief visual mask and then you'll see a second picture.
And all you have to do is say whether the second picture is the same view as in the first picture.
Whether it's closer up or further away.
Okay.
So I believe you have some voting pads
So if we could have a look at the voting pad options. There we go.
So you're going to press button A if you think the second picture is closer up.
You're going to press button B if you think it's the same.
And you're going to press button C if you think it's further away.
Okay.
Don't worry, we'll remind you again before you have to make your decision.
And that's not even the memory test.
So if we could go back to the laptop now.
Right.
So are you ready?
It's going to be really quick, I'm not joking. Okay?
Right, if we could have the options up again please
Now.
Was the second picture closer up, the same, or further away?
Blink and you miss it!
So you should go with your gut instinct on this now. Don't over think it, over thinking it is bad.
I'll just let everybody finish their voting.
Have a guess if you're not sure. A, B, C.
What do we think?
All done? Everybody finished?
Good? Okay, Let's have a look at the results if we may.
Okay, so we see that a lot of you thought that it was closer up.
And we see that some of you thought that it was the same.
And a smaller number thought that it was further away.
Okay.
We're gonna do another one. So anyone who missed it
Press your buttons.
Right, let's, uh
Let's go back to the laptop if we may.
Right. Okay. Don't blink, you'll miss it.Here we go.
Right, if we could have the options up again.
A, closer up.
B, the same.
C, further away.
Okay, let's see what we've got.
Okay, very similar.
Somebody's invalid but we won't go into that.
There's always one.
So you can see we're actually quite consistent across the two tests. We've got around the sixty percent mark of people thinking it was closer up.
And we have some people thinking it's the same and a few, much fewer thinking, that it was further away.
Okay, if we could go back to the laptop.
Okay. Now.
I have to tell you that in fact on both of those tests
the second picture was identical to the first picture.
And sixty percent of you got it wrong.
There was a quarter of a second delay between the first picture and the second picture.
And you still got it wrong.
That's not very good memory is it?
Well, I'm going to explain a bit later on why so many of you made that error.
But what it illustrates is that memory is not a faithful record of the past, even when the past was a quarter of a second ago.
It's not flawless, its fallible.
But in fact these sorts of errors are built into the very structure of the memory system and for good reasons.
In a similar vain, we often bemoan the fact that we forget things and we'd love to be able to remember more. But be careful what you wish for.
A number of years ago, some rare individuals were discovered that never forget anything that has ever happened to them.
And this has come to be known as highly superior autobiographical memory.
Now I'm not talking here about the sorts of people who enter the world memory championships.
You know, the sorts of people, they can remember pi to 67,890 decimal places. I think you'll find is the current world record.
Fascinating as they are and we've studied them
But in fact those sorts of people typically use mnemonics or strategies and they practice and they practice so it's very effortful.
I'm talking, instead, about people like this.
*reads text on screen*
So you can appreciate that remembering absolutely everything is not desirable and we should rejoice in our normal forgetting because believe me, it is a good thing.
So, we have established that there are different types of memory.
That memory is designed to work in the context of our existing knowledge.
That memory is not perfect, that there are errors.
And the question we need to ask is, "why is memory like this?"
Well it has to do with the other scurrilous claim I made earlier which is that memory is not really about the past
and to explore this, we need to turn to the brain.
Here is the brain in all its glory, thanks to the wonders of magnetic resonance imaging or MRI.
And you can see here the sorts of detail and views of the brain. Here we're face-on, here we're side-on,
here we're looking down through the top of the head.
We can see the grey matter, the white matter. We can appreciate the complexity of the connections between brain areas.
Now the formal study of the brain basis of memory really took off in the 1950s with this patient, H.M. or Henry Molaison.
Now poor H.M. suffered from intractable epilepsy.
And in order to alleviate his seizures both of his temporal lobes were removed.
And you can sort of see the black areas here is where his temporal lobes use to be.
Now the surgery did indeed reduce his seizure frequency
but it had the unintended and devastating side effect of making him densely amnesic.
So after the surgery, he couldn't form any new memories. He lost much of his past.
But he did retain factual knowledge about the world. His short term memory appeared to be fine.
His general intellect was fine as were his social skills.
So he appeared to have this selective loss of his autobiographical or episodic memory.
So contrast this with the description we read earlier of the patient with superior autobiographical memory.
So H.M. is asked
*reads text on screen*
Now at the time his deficit was linked to one particular part of the temporal lobe.
And that part of the temporal lobe is the hippocampus.
Which you can see here, deep in the temporal lobes there in red, circled in red here in this little cartoon
and circled in the three views in the MRI scan.
And it's called the hippocampus because an early anatomist likened it to a seahorse.
This is a slightly icky picture of a hippocampus taken out of a human brain but to illustrate that it does look quite like a seahorse or hippocampus.
Now in fact you can hopefully see that H.M.'s surgery took away a lot more than his hippocampus
so his memory problems cannot really be linked with certainty to the hippocampus.
However in subsequent decades we have located patients who appear to have selective damage of just the hippocampus on both sides
as far as our current anatomical imaging can tell us.
And they have very similar profiles in terms of their memory preservation and impairment as H.M.
And of course studies of healthy subjects where we infer neural activity from blood flow on functional MRI or FMRI scans
confirm the engagement of the hippocampus along with other brain areas
when people recall their past experiences.
So the hippocampus is necessary for helping us recall our autobiographical memories
those personal memories that make our lives.
But in a different domain, the hippocampus was also under scrutiny.
Because in the 1970s, physiologists recording from single neurons in the rat hippocampus made a startling discovery.
They found that there were cells that seemed to respond to specific places in the environment.
And this is irrespective of where the rat was looking.
And these place cells as they came to be known seemed to in some way embody the memory of that particular place.
Now on the right here, we're looking down at a round arena and you can see a little cartoon rat there.
And what I'm going to play now is a movie and what you'll see is you'll see the rat moving around this arena
and what you'll hear is the sound an actual place cell firing.
And you'll see that this place cell likes one particular part of the environment.
So you can see he's looking all over the place, even when he's in the northwest of the arena.
But that place cell, he's loving the northwest.
Now the rat is going to speed up a bit. I just sped it up but just to save time. He's not manic or anything, so.
But you can see just how specific it is. So even though the rat is going all over the place its really focused on this part of the environment
and then you have of course place cells that cover all different parts of the environment, thus appearing to map the spatial location within that environment.
So here we have a situation where the rat hippocampus, at any rate, seems to be fundamentally involved with processing space.
Now since this discovery many studies have examined spatial memory in humans.
Now for example, in my lab we took advantage of this commercially available video game. Some of you might know, it's called "the Getaway."
It's made by Sony.
And they set this video game in central London. And you could navigate within it.
And at the time it was a pretty faithful simulation of London including most of the roads, and the shops, and the buildings.
So we had subjects find their way around London and in this virtual environment while their brains are being scanned.
So obviously we can't really look at navigation normally if people have their heads fixed in a brain scanner, they're not going anywhere.
But this way we could use this virtual navigation as a proxy for real navigation.
So now I'm going to show you a movie of the results of one of our experiments.
And what we were able to do was we were able to relate the thoughts that people were having during navigation with the brain activity on the FMRI scans.
So on the bottom left you're going to see where the person was actually navigating.
This is one of the subjects navigating.
Here's a little sort of overview to show you where they're going to go.
You'll see the thoughts they were having appearing in thought bubbles up here
and then you'll see the FMRI activity that was occurring at the time of those thoughts.
Right. Now the hippocampus comes on very quickly at the start. So you'll have to be quick to see it.
Because it's involved when you plan and visualise your route when you're about to start.
Okay. So there's him saying he needs to go to Peters Street. So there's the hippocampus, so he's off now.
So now we're moving down Shaftesbury Avenue.
Decided to change routes so some of the frontal areas come on.
Ah, now, there's a blockage. He's gotta take a different route.
So he's coasting along.
He's planning, his cerebellum comes on, he's gotta take this corner carefully.
Now you'll see look at all the swathes of visual cortex coming on because he's thinking "God these shops look colorful."
Then he's thinking, "Yeah I should see this." Oh there it is. Good.
And then a little bit of road rage just to end with there.
So you can see that
Virtual navigation, and we believe, actual navigation activates many brain areas but the hippocampus in particular
seems to come on when you're engaged in visually planning your route.
Now, we also used this virtual London in another study.
We had the chance to test this patient, patient TT.
He's an extremely rare patient and he had damage primarily restricted to his two hippocampi.
so you can see sort of see the holes where his hippocampi should be.
And naturally he was densely amnesic as a consequence.
Crucially before his illness, he had been a licensed London taxi driver for forty years.
So the question we were able to pose was,
"How would his hippocampal damage affect this long standing navigation skill and his knowledge of the spatial layout of London?"
So here I'm just showing an example trial and what the subjects had to do, including TT,
was get from St. Paul's Cathedral to the Bank of England.
Easy peasy if you're a cab driver.
And indeed the ten control taxis drivers who were the same age and the same level of experience as TT
look at that, they all took the same direct route. No errors whatsoever.
Now in black we see the route taken by TT
and you can see that he's going all around the houses. He cannot get there and in fact he doesn't get there.
And this was the same in trial after trial.
So they were virtually navigating around London but he couldn't get there.
And the astute amongst you might have realised something about his navigation. In fact, he's using just the A roads.
The big old A roads. And he cannot navigate on the smaller roads.
So he seems to have lost the finer detail of the smaller routes and he couldn't visualize them in his route planning.
Now of course we had already shown that the back part of the hippocampus, the posterior hippocampus
was larger in London taxi drivers than in non-taxi drivers, including London bus drivers.
And more recently we did a longitudinal study where we took trainees who were learning the knowledge
thanks to the cooperation of the Public Carriage Office
And so we studied them before they started learning the layout of London.
and then we got them to come back when they qualified.
Now interestingly, about fifty percent qualified and fifty percent failed to qualify and we also had a control group.
In those who qualified, we saw increased volume in the posterior part of their hippocampus.
At time two, three and a half years later, compared to time one.
And in those who didn't qualify, we didn't see any changes.
So these sorts of studies demonstrate the plasticity of the adult human brain in response to the environment stimulation.
So the brain is not fixed, we can change it by what we do.
But it also underlines the relationship between the human hippocampus and space.
Okay so here we have this brain structure then, the hippocampus, that doesn't work along, it's part of these larger brain networks
concerned with memory, but it nevertheless appears to be particularly critical for autobiographical memories but also for spatial navigation.
And we see devastating effects on these cognitive functions when the two hippocampi are compromised.
And the hippocampus, it turns out, is vulnerable of a whole range of common pathologies.
Strokes, epilepsy, dementia, including alzheimers disease, loss of oxygen to the brain or anoxia,
and certain types of brain infection.
So what is the hippocampus doing that makes it so important for recalling the past and navigation?
Two seemingly different cognitive functions.
Well in the last number of years we've begun to unravel this somewhat.
And once again, the insights come from studying patients with selective damage to the two hippocampi.
And as you would expect, these patients were amnesic, they couldn't find their way around.
But this time we asked them a different question. We asked them to imagine an experience that might happen to them in the future.
So not the past, we know they can't do the past. But what about the future. They couldn't do it.
So then we said,
well these patients can't recall the past, they can't imagine the future; they're stuck in the present.
They cannot travel through time mentally speaking.
We then asked them to just to imagine a simple scene. So not one that was set in the past or the future, and they couldn't do that either.
Now they could imagine single objects so it wasn't just a problem with the basic ability to imagine. They could imagine single objects in their mind's eye.
But they couldn't imagine scenes.
Now I'm going to show you one patient's attempt to construct a scene.
So here it is. The patient was asked,
Imagine you're lying on a white sandy beach in a beautiful tropical bay.
So there is the patient on top, P03. So he says,
*reads text on screen*
And below that I've just put the scene created by a control who's age, gender, IQ matched the patient.
I won't read all of this but you'll see quickly that the control said,
*reads text on screen*
So there's a huge difference between these scenes. The control scene you could quite happily step into.
And who wouldn't want to be stepping into a beautiful tropical bay.
But the patient's scene, it's very fragmented and indeed, they rate their scenes as spatially fragmented and lacking in coherence.
And when we ask them, "What do you think the problem is that you have?"
And here's some very insightful comments from the patients.
*reads text on screen*
Now, FMRI of healthy volunteers also show that the hippocampus is indeed engaged when imagining fictitious or future scenes
Now based on these findings we suggested that the hippocampus is needed for scene construction
that, it facilitates the construction of complex spatial contexts or scenes into which the details of our experiences then get bound.
And we proposed that this process underpins episodic and autobiographical memory, imagining, thinking about the future, and spatial navigation.
Now just to be clear I'm not saying the hippocampus does all of these things alone.
There are many brain regions responsible for these cognitive functions.
But what I'm suggesting is despite all the differences between these, the memory, the spatial navigation, the future thinking, and so on
they each require a special ingredient supplied by the hippocampus and I'm suggesting that's the ability to mentally construct scenes.
And if you think about it, whenever we recall the past or thinking about something we're going to do in the future
or we're planning a route somewhere, it invariably involves us conjuring up scenes in our mind's eye.
So, this may seem like heresy, but the hippocampus which has for so long for sixty years been portrayed as the quintessential memory device
may not actually be about memory per se, but instead memory relies on an ingredient from the hippocampus as do other types of cognition.
Now, we recently discovered something else about scenes and the hippocampus which I can hopefully illustrate
if I have ten willing volunteers from the audience.
So what I'm going to do is show you a picture, you can do this, imagine you're doing this
I'm going to show you a picture, I will you give you 15 seconds to look at that picture, and please know I am going to test your memory for that picture.
I have a stopwatch, no psychologist goes anywhere without one.
Right, are you ready people with clipboards. Don't do anything.
You keep an eye now, make sure nobody is cheating.
15 seconds, take it in. Take in as much as you can.
Off you go.
Okay. Please draw what you remember of that picture.
Quick sketch now. Not looking for John Constable.
When you're finished, can you hold you clipboard up in the air, and one of the gentlemen will collect it from you. Okay.
Thank you.
Okay. So. With the permission of the volunteers, I'm now going to now share these with the audience if that's okay.
Anyone shout out if they're not happy. No? Okay, that's fine.
*laughter*
Don't worry, we don't have anyone's names on them.
Are we ready for this?
Okay.
Now let me zoom.
Ooh, hello. Right.
Very good.
You'd know they were banana's, right?
Good. Okay.
Now let's have a look here.
Okay.
*laughter*
Well you know, you'll see it's not bad, it's not bad.
Okay.
And there we have
some other ones, capture the shape there nicely. Very good. Excellent.
And we'll do this quickly.
Good. No? Come on. People laughing weren't drawing I notice.
There we go, lovely. Very nice.
Ooh now look at this. Went very very big on the old background there.
Very good. Very good.
In fact all of our volunteers deserve a nice round of applause.
That's quite sort of slightly deconstructed one there.
Okay.
Now. I'm not quite sure what way to put this.
Well we get the drift, we get the drift. Very good.
And again very nice on the background there.
And then we'll end with this one.
Very good. Okay. Now.
Excellent efforts I think you'll agree under intense scrutiny.
But I wonder did you notice something about these drawings. There's something not quite right.
I'm not going to psychoanalyse people on the basis of these. That's a whole other discourse.
But if we can just go back to the slides, are we still on them. Okay let's go back to the drawings, see if we can identify what's not quite right.
Okay so there we have the bananas. Now look at the bananas, people.
These are big bananas, these are in your face bananas.
These are bananas that take up much of the picture.
Now, let's go back to the visualiser.
These aren't big bananas, these are little bananas.
Little tiny bananas.
Or little nano bananas.
In fact, if we look at all of these diagrams or pictures, you'll notice that everyone has put in a lot more space around the bananas than there was in the original picture.
And there's a very good reason why people did this.
What you've demonstrated, our volunteers, is a phenomenon called "Boundary Extension."
Now boundary extension is a robust and consistent memory error found in adults and children.
But it only occurs in relations to scenes and not single objects and it occurs for this reason.
When we initially encounter a scene
we're not limited to the direct sensory input coming into our eyes but we also have an access to a wealth of prior knowledge
about the world and so we automatically extrapolate beyond the borders of what we see.
And we include this extra bit of extrapolation into our mental representation of the scene.
And that's why you all included more space around your bananas.
Its also the reason why sixty percent of you made this error in the earlier test.
Because when you saw the first picture, you extrapolated beyond the view automatically. You can't stop yourself doing it.
And that became built into your mental representation of he scene.
So here's what you added to it and this is what you ended up with in your head.
So when the second picture came along it now looked much closer up than the actual picture you were comparing it to.
Even though it's exactly the same as the study picture. And you only had a quarter of a second gap between the two.
In fact, you only need as little as 42 milliseconds gap and people still make this error.
So boundary extension depends on scene construction
because you have to imagine and construct what might be beyond the view. And while it might be an error, it's a highly adaptive error
because it allows us to rapidly embed the world which we're only able to sample a little bit at a time into a wider, larger spatial framework
thereby giving us the experience of a seamless and continuous reality.
Now we've recently found that patients with selective damage to the hippocampi and amnesia
show greatly reduced boundary extension. So if we take a couple of the pictures from our drawing task
you'll recognise the bananas.
Here is the performance of two of the control subjects. And you'll see those bananas, they look quite similar to some of these bananas.
Lots of extra space around the bananas.
And here's the picture from one example patient.
You can see the patients make much less of an error, they include a lot less space.
And if we look at the rapid picture test. So here I'm showing you the patients in red and the controls in blue.
You can see that on sixty percent trials the subjects,  the controls, thought it was closer up. They made the error you made.
Not the patients though. No, they knew it was the same picture. They got it correct.
So paradoxically, tests like these show that patients who are profoundly amnesic actually score much better on memory tests than healthy controls
because they can't make the error. They can't imagine what's beyond the view.
So patients with hippocampal damage, and this includes patients with dementia and other pathologies, not just the selective cases we have here.
But they're not only contending with problems recalling the past, with navigation, with imaging fictitious and future scenes or scenarios
they are literally stuck with what's in front of their eyes.
Deprived of a level of subjective continuity, unable to even visualise what's behind them or what's around the corner.
And so this leads us to the actual reason for memory and the function of the hippocampus.
Memory is not about the past, its about the future.
It's about helping us predict and infer, based on previous experiences and prior knowledge, what to do next.
Where to go. What to do. What to expect.
And in this way, the purpose of memory, the hippocampus, indeed the brain, is survival.
And this was actually preempted quite a number of years ago.
In fact, in 1798, one year before this institution was founded, Immanuel Kant said,
"Recalling the past only occurs with the intention of making it possible to foresee the future."
Or to put it another way; as the White Queen from "Through the Looking Glass" observed,
"It's a poor sort of memory that only works backwards."
So memory works best in the context of our prior knowledge and yes, it makes errors but that's what makes it so powerful and flexible
it's not a perfect record of the past. It's constructed and reconstructed depending on the state of our knowledge and the state of the world.
And I suggest that a key part of this process is the construction of spatially coherent scenes in the hippocampus that form the basis
of our personal and of course our shared past.
So I'll conclude by mentioning that the story doesn't end here.
We want to know more about these processes and mechanisms, the memory traces that arise from them.
How these memory traces change as we age. How do we examine them in the contexts of brain injury and disease.
Well, using the latest high resolution functional MRI scanning, and new decoding algorithms.
We've been able to predict solely by examining the patterns on FMRI scans and particularly in the hippocampus where someone is located in a virtual reality environment.
So we can know where they were just by analysing the pattern of their brain activity.
We can also tell what specific memory they're recalling
be that movies that we've showed them before scanning or indeed their own autobiographical memories. We can predict what they are recalling.
So these exciting new technologies will ensure that the future of memory research is an exciting one.
And so I will end by thanking all the people and the funders who make research like this possible.
Thank you all very much for participating, particularly our volunteers. And thank you all for listening.
*applause*
Thank you so much for a fantastic discourse. I've got to say, I love it when I come to these events
and I actually find out so much more than I ever knew before and it's quite amazing.
So we've got about twenty minutes of questions so if anyone would like to ask something just stick you hand very high in the air
and wait for the microphone to come to you please. So just start off with this gentleman in the first row. Thank you.
Given that 35 percent of us pressed button B, is that by chance or are we all early onset dementia?
Please don't worry sir, I don't want to send you thirty percent of, let's face it, successfully doing the task accurately.
No, I mean we've only just done two and there are some, you know we do a lot more in a complete trial
For some people, some boundary extension effects are elicited more strongly on some stimuli than others.
It all comes out in the wash, don't worry. The patients as you saw performed much more differently than the control.
I'm gonna swing over to this gentleman in the purple tie.
Thank you very much. Very interesting lecture.
I wondered if any work had been done with novelists or similar people who create pictures but in words
and whether that involves just the same bit of the brain or if there are other bits involved when you try and do that.
It's a very interesting question because everything that I sort of presented today is very visual.
And a lot of the theories about memory, including our own scene construction theory relate to memory that's spatial or visual
and the question you're asking is an excellent one. What happens in terms of verbal material.
Now patients with hippocampal damage also cannot recall stories that are told to them.
Or if they read them and it's interesting that the patients when we're chatting with them, they say,
"I can no longer read. I use to love books and now I can no longer read them."
And it turns out that they can't imagine the events as they're unfolding.
So it seems to come back to translating the verbal into a visual modality to help them sort of with the plot in the story. So, good question. Thank you.
Do we have anyone else in the gallery Martin?
Alright.
Ooh, very good.
My memory is so appalling that I don't even remember exact name of the disorder you mentioned early in the lecture
where people have an extenuated ability to remember, such that they refer to it as being a burden.
That is the first of my questions in relation to that. What percentage of the population, it might even be a number of people, would actually have that?
Because that's, it is quite extraordinary.
It's quite extraordinary, and many many years ago a famous neuropsychologist called Luria first really documented the first case of this.
But in recent times the group in California, they have now found about twelve people since this sort of research has become famous
and they've been asking people to get in touch.
And they found a lot of people with really really good memories but only about twelve seemed to have this phenomenon so
it's very difficult to estimate on that basis, what proportion of the population it might be.
It's still very early days in trying to unravel exactly what it's about.
Thank you and obviously very different from people saying,
"Oh he has a photographic memory, he remembers everything which is a different..."
It's a different thing and you know, memory comes in different shapes and sizes for all of us you know
some people have very good memories, some people less good memories.
I just have one other question too, just in relation to the people who can't remember.
The gentleman you mentioned who had a part of his hippocampus removed to treat his epilepsy.
Surely they have an emotional response, a frustration for not being able to remember or is that taken as well?
I guess that's a subject for a number of lectures.
Yes. It is interesting. I mean that they definitely know that they have a problem
You know, they know they have a memory problem. But when you talk to them and you interact with them
obviously when they came to see us, they're very motivated to be there, they often forget through the day why they're there.
But they're very very appropriate emotionally and socially but of course that doesn't mean that at some level they don't feel loss
they definitely know they've lost something and they've lost their independence you know they can't live independently anymore.
It's terribly devastating.
And just finally my last question...
Sorry can I just interrupt there, you've had two very good questions but many many down there, maybe you can't see them from up there.
Someone in the, the lady in the red. Just there please.
If one could imagine something like a scene but you can't feel the sand, you can't feel the heat
but you can plan for the future, from that information what would you deduce is right or wrong with the brain?
So you think that there are people who can visually... so you can visually imagine the scenes
but you can't imagine the sort of touch or feel? Okay well we haven't really gone into that in very much detail.
Our scene construction theory is a very recent one so we're still finding out a lot more about it
and that would be very interesting to think about the multi modal nature of scenes
the fact that you hear things, you smell things, you touch things, and you see things.
What I will say is that the boundary extension effect where everybody put more space
we also did another version of that test where we took away vision, so we blindfolded all of our subjects
and we had them feel scenes and we took the borders of the scenes away and they had to put markers down where they thought the border of the scene was
again they put way too much space in. So the point of that is that it isn't just being driven by vision,
it also occurs in the context of other modalities. But we do need to learn more about how those modalities get and combined into the full experience of a scene.
And I saw a question, oh there's two here. Maybe the gentleman on the end and then the gentleman behind.
Does a place cell when they fire help to create the memories?
That's a really good question.
So place cells have been around for a long time. They've been really really researched a lot.
But we still don't quite understand how they do what they do and what their precise relationship is to memory.
So we don't know exactly what happens. We do know that place cells map the environment such that the environment gets covered.
We know that the hippocampus' next door neighbour, a part of the brain called the entorhinal cortex, has different types of cells
called grid cells which fire literally in grids across an environment.
It seems to me as if it's like a database where it's put in a memory somewhere into the brain.
Well it's difficult, we just don't know. We know that this type of cell in rats is mapping the space. It's much harder to map these things in humans
we can't just stick electrodes in. Where people have been having surgery again for epilepsy, sometimes they record intracranially
to try to find the focus of the seizure.
And sometimes those electrodes are put into the hippocampus and people have found responses that look quite like place cells
so we think there are also place cells in humans. And then the question is what are they doing,
is it that space underpins all of our memories, underpins scenes and so on.
And somehow it's creating the memory of that spatial context which then all the other bits of memory get added too.
We don't know.
Thank you.
So two rows behind the gentleman with his hand stuck up.
Thanks, I'm quite interested in this rat.
My manic rat?
Yes, you're proposing really that the hippocampus has got a lot more active role to play in memory
it's not just this sort of memory storage device, intrinsically related to autobiographical memories.
And also looking forward to the future. And to me an autobiographical memory is sort of intrinsically related to a sense
what makes us human, is it that we have this very strong idea of identity in who we are.
But given that we share hippocampi with rats and presumably alligators and other things
what can you say about what these other animals might have in terms of a sense of self given that the hippocampus seems to be much more
than a database?
Very good question.
Autobiographical memory are our personal past. They're very important to helping us develop a sense of self.
But interestingly, people who are interested in the self have done lots of other studies.
And they've found that in fact issues to do with ourself, our perception of ourselves, things that are self relevant
how we evaluate ourselves are more likely to involve areas of frontal cortex, not the hippocampus.
Now I think when we retrieve an autobiographical memory, of course we know the hippocampus is talking to the frontal cortex
they have a lot of interactions. And so the frontal areas may be the processing part to do with the sense of self.
And that could make sense if you then look at the hippocampus across species
because the hippocampus is quite well preserved across species.
You look at a rat hippocampus and a human hippocampus you can see they look quite similar.
And so the suggestion would be that the algorithms playing out in a rat hippocampus are likely to be also playing out in a human hippocampus.
And maybe the sense of self which we don't know if a rat has a sense of self. But we do know that is has much much smaller
and some people would argue doesn't at all have a frontal cortex.
So the other interesting thing to say is that in recent years, the people who record from in the rat hippocampus
have found not only activity of the place cells when the rat is moving around in the place but also preplay
where rats are put in a position where they have to make a decision in the future. The place cell seems to, the firing seems to sweep
ahead of the rat, almost like its trying to plan for the future and that's called preplay.
So again that would fit with what we're saying for the hippocampal side of things and then maybe things to do with the self are a bit more in our big old frontal lobes.
Okay. I'm just gonna just take... your hand went up so quickly then I couldn't...
Just... the boy there. Thanks.
And then I'll take two from over this side after that.
So more on the rat basically.
Oh, I don't study rats but I'll do my best.
So I didn't understand what exactly was a place cell doing because the rat going around the place and the place cells were firing but it didn't seem to affect the rat's behavior any.
It was still going around completely normally.
Yes so the rat in these situations normally, what they have them doing is going around foraging for a little little snacks or treats.
And they're measuring the place cells so the place... obviously the rat does what he does.
He probably has other place cells that are firing when he's in other parts of the environment but we just didn't hear those recordings.
And so basically his hippocampus is automatically mapping the space for the rat.
And so if we could hear all of the place cells we would hear a symphony of firing but we only hear just one just to show you how specific they are
and how they're not visually dependent. So the rat could be looking in a different direction
but once he's in that part of the environment, the place cell fires.
Okay and there's a lady right there, thank you.
Hello, thank you very much, that was extremely interesting.
I'm just wondering how much, and I've had to look up on my little Google on my phone because I couldn't remember what they were.
How much you took into account the learning styles.
You know, the logical, the kinesthetic, and the visual.
Because I work with people and I take people sometimes on a guided imagery path.
And I know that there are lots of people who would say at the end, you know,
they wish I was less descriptive because they were thinking they were on a palm tree beach
and I was describing a mountain spring.
And there are other people who would say, you know, I just couldn't.
I wish, you know, they'd rather I said more because they couldn't imagine anything more than the man who had the damage.
And so my experience has been, unless these people have got damage that I don't know about, and I don't think they did,
my experience has been that there are people who actually don't have that visual capacity and that creative imagination
and I wonder how that plays a part in all of your research and the actual science of it as well.
I think that's a really excellent question. So again this is all fairly new stuff
and what we want to do is exactly that. We want to try and find out about how well or otherwise people generally can imagine and construct scenes.
And we want to try and relate that to their memory performance and their navigation performance to do exactly what you said
and I suspect that what we'll find is that there are people who find it very difficult to visualize and we know that
because even in some of our studies so far, we've tested, you know, healthy controls who found the task very difficult.
and so the question is, is that impacting upon their memory ability and are they the sorts of people who end up
with poorer memories than somebody who can imagine things quite well.
So watch this space, we'll let you know.
Okay there's someone just directly behind you, did you want to ask a question? Your hand was up earlier.
No? Okay. I'll take somebody up in the gallery, I saw someone waving their hand in the gallery.
Hello. Hi. Sorry about the rat again but two rats now in the same environment
if you map the place cells of the first rat, the second rat with the second part of the same place cells
or will they be different with each rat?
Well I think with... so it's an interesting question.
So everybody's neurons are their own and including a rat, and so I think you couldn't infer something from one rat's place cell about another rat.
And that you know that's true also of people. So if you don't mind me bringing it back to people just to answer the question.
So at the end I alluded to the fact that we're able now to look at activity in FMRI scans while people are recalling their own personal past
and we can predict just from the activity, we know what memory they're recalling.
And everybody has their own personal past and the memories are unique to them
and so, you know, the set of neurons I activate for my particular memory are gonna be very different to the neurons you activate for your memories.
And that's one of the pluses of this new approach is that we can look at everyone as an individual
and we can see exactly how their activity maps onto their psychology if you like.
So now I'm even more amazed that we're all so interested in rats.
I mean clearly we're gonna have to...
I have to say I normally don't get many rat questions.
But sadly we're reaching the end of the time for questions.
I'm really very sorry, I know there are lots of you with your hands in the air.
I just... we just don't have time to have any more questions I think.
Thank you all very much for coming, we'll see you here again the next discourse or even maybe one of the public events before that.
Thank you so much for those people who did ask those questions and stimulate the kind of discussion and debate.
Which I think is wonderful in this small sort of space here.
And once again if you'd like to all join me in thanking Eleanor for a fantastic discourse.
*applause*
