Dave: It’s sometimes tricky and most times tough, being me and remembering all that stuff. Keys and dates and phones and things. Most of life’s important things. Up and down the stairs I go. When I get to the top - why? I don't know.
I search the bedroom looking for clues. Something to jog my brain into use. Here it comes - I remember it now. [Instrumental music begins] We've got it right, my brain and me. It's finding the smallest things that can fill you with glee.
[Music continues, then fades.]
Cristina: That was Dave, a person who experiences memory loss due to acquired brain damage. He was part of a panel discussion here at the Crick during the Science on Screen festival, alongside other expert voices: Vaughan Bell, a neuropsychologist from UCL and Crick scientist Julia Harris. Vaughan started by telling us more about where memories are stored.
Vaughan: So the question about ‘where are memories?’ - I don’t think is a great question, actually. If you study the brain, the question sounds a little bit like ‘where does economics happen?’ And you might go ‘well, I don't know - maybe the City of London or maybe in the Treasury or maybe in the banks’.
But actually, economics happens everywhere. Economics happens between individual people and there are bits of society that are specialised for economics, like the banks and the treasury and so on and so forth. But that’s really what the brain is like. So memories happen even between two single cells - something Julia spends a lot of her time researching - on this very small level. But there’s also bits of the brain that are specialised for certain processes of memory, and so really we can think of memory like that.
Memory is the fundamental function of the brain cells but actually there a bits of the brain are specialised for different processes just like banks and the treasury are specialised for different aspects of economics.
Julia: A new memory will involve the strengthening of the synaptic connections between all of the cells that are involved in that memory, and that would mean that all of these cells are more likely to fire or ‘activate’ together, creating a neural representation of this memory. And if those synapses become weaker, then the neural representation becomes weaker, and we can forget.
This is something we understand quite well on the cellular level, but what we know much less about are the specific conditions that would cause strengthening or weakening of specific synapses, and how exactly that relates to our experience of remembering and forgetting.
Vaughan: There are different forms of amnesia, but there’s a common one that happens after brain injury where people are unable to lay down new memories, and that’s how we mainly understand amnesia, sometimes called ‘anterograde amnesia’. And so imagine if you couldn’t create new memories. Everything that happens, you wouldn’t be able to store as a memory.
People who have really dense amnesia, to the point where anything past 20 seconds is kind of lost to consciousness. There are some famous cases of people, like Clive Wearing, who actually had herpes encephalitis, and lost the ability to recall new memories and would constantly write in his diary ‘I feel like I’ve just woken up for the first time’, then he would cross it out and write ‘I feel like I’ve just woken up for the first time’, as if he was constantly becoming conscious.
Now it was originally thought that actually that would mean you had lost the ability to learn anything, but actually through some experiments done with the likes of HM and CW - really famous amnesic patients in the literature - they did experiments where they asked them to learn new skills, where they had to learn new ‘procedural memories’, as they’re called. This is literally learning how to do procedures, like riding a bike or learning something new. And they could learn just as well as people without amnesia.
And what this tells us is that there are different processes and mechanisms and forms of memory and just because we lose the conscious ability to have new memories, it doesn't mean that we’re completely unable to learn.
Dave: I became a very different person - a very different person - one that my wife said she probably wouldn’t have married. It’s a big problem for people with acquired brain injuries - the change of identity and self after whatever’s happened to you is enormous. When I came out of hospital, I thought I was Snoop Dogg. I wanted to wear velour tracksuits and have diamonds. So different to the way that I am now, and was before.
It’s not all bad, not being able to remember the music you liked, having the experience of rediscovery like first time - watching movies, reading’s a little tricky. All that kind of stuff is a new discovery. There’s always a downside to a lot of stuff, but it’s always far outweighed by that feeling of glee of finding something, it far outweighs losing it. And self-identity is something you can grow back into as a very different new person.
I woke up about three years after my brain injury one morning and went ‘I’m going to be an artist’ and it just felt like somebody opened up a filing cabinet in the back of my head. It could have been music, it could have been anything, and it was art. And now I walk around and all I see is creative opportunities. It takes up a lot of my brain input, but in a very, very nice way. [Instrumental guitar music begins.] That’s my attempt at mindfulness: being able to sit and focus and do stuff in a creative way.
[Music fades away.]
Cristina: At the end of the panel, there was a Q&A from the audience, and Julia finished by answering a question about whether people’s descriptions of their own dreams are useful in understanding the processes of memory formation
[Instrumental music begins.]
Julia: You’ve got your Freuds who say that the content of dreams is important for…whatever he said it was important for! Then you had a long period of people who were saying ‘no, probably the content of your dreams is just an epi-phenomenon of what the brain is doing, it doesn’t mean anything’.
Now you have other people who have started to do some really interesting research trying to track what exactly about your day is replayed in a dream, and together with this kind of evidence that we have from mice, showing that they are replaying experiences, and if you put a mouse in two different mazes, during its sleep it can actually combine them. We’re starting to think that maybe dreaming is an important stage for us to, say, rehearse decision making. Where I think a lot of the really interesting neural changes that are happening during sleep are going on, is deep sleep.
And this is where you have some really interesting brain activity patterns that are not normally seen during wake, so you have these high amplitude, low frequency oscillations where all of your neurons are coming on together and then going off together.
And we know that this kind of activity can change synaptic connections in one way, and then you see high bursts of activity that can change connections in another way. It’s actually these activities in deep sleep, where you usually see ‘replay’.
I think there’s a lot of different ways during sleep that the brain could be using different activity mechanisms to be changing itself, updating itself, so that when you wake up the next day, you’re more prepared for the world.
[Instrumental music]
