How does aphantasia affect autobiographical memory?

Close your eyes and picture what you were doing at breakfast time today. Most people can do that in, literally, the blink of an eye. We can summon up an autobiographical narrative of where we were, what we were doing, who we were with, and the order in which those things occurred. They accompanied by rich visual pictures of the events. But some people can’t do this. It’s a condition called aphantasia, and Cornelia McCormick, from University Medical School, Bonn, has a track record in studying it. As she explains to Chris Smith, she was wondering how being aphantasic affects a person’s memory, and what differences brain scans might reveal when individuals with the condition try to recall things about their lives…

Cornelia - Most of us, if we think about important events of our lives, our marriage, when my children were born, I have very vivid mental imagery in my mind's eye, and in the memory research community there's this understanding that those vivid imagery are really important for autobiographical memories. And one of the questions we have, if the images are missing, can we still remember and what do we then remember of our own lives? And that's when we turned to aphantasia together with the aphantasia research project of the University of Bonn, Merlin Monzel. We got talking and he said, well, why don't we sit together and work on how aphantasics - so people that don't have mental imagery, don't have the images in their mind's eye - then remember autobiographical memory.

Chris - What was the next step then? So having decided this was going to be the group to study who could help you answer that question, how did you put the study together? What were the questions you were trying to ask and how?

Cornelia - Our study had two important parts. One is an interview of autobiographical memories. People are asked to explain in much detail five autobiographical memories. So which detail comes to mind when you remember important days of your life. And then we put people in the MRI scanner and here we were particularly interested in which parts of their brain are activated when they remember their memories.

Chris - Presumably you are comparing people who do and don't have aphantasia and you can then ask, well, which bits of the brain are connected together? Are there any differences in these connections which are flashing up?

Cornelia - Yeah. So we had very strong hypothesis about which brain regions may be involved in this task. We thought the hippocampus is really important because the hippocampus has a longstanding history of being the memory hub of our brain. And the other important brain region is the visual perceptual cortex. So there at the occipital lobe where we process vision in our brains and those two brain regions, hippocampus and occipital lobe, those were the key areas we wanted to investigate. And hypothesised that there are differences between people with aphantasia and people who have mental images in their mind's eye.

Chris - Well, let's begin with what we would dub normal, the people who do have the mental images in their mind eye first. When you do these functional imaging studies, what flashes up in those regions you're interested in, in those normal people?

Cornelia - Well then we can see a strong hippocampal activation and also activation in the occipital cortex. There are also other areas of the brain activated when you remember autobiographic memories. But these were the areas that we were specifically interested in.

Chris - And so a loose interpretation of that is that when you are remembering things and presenting them to your consciousness, because it's got a visual element, the visual system flashes up. Would that be an initial interpretation?

Cornelia - Yeah, so the theory behind it is that the visual or the occipital cortex is providing all those vivid mental imagery details that you need to actually see something in your mind's eye. And the hippocampus is more the hub connecting memories and also providing and constructing a mental scene in your mind's eye.

Chris - And so one would hypothesise then that people with aphantasia who don't see the images might try to compile an experience through their hippocampus and recall a memory, but they wouldn't have any visual activation to the same extent because they're not seeing anything in their mind's eye?

Cornelia - Exactly. So now we are going to the really exciting results. So I would like to just go back to the interview one second because that's already very interesting what happens in the reports of their memories. So here we find that not only are the visual details missing to the autobiographic memory, the whole memory system seems to be impacted. So they also have hardly any emotional details to their memory and they had a hard time remembering memories at all. So it's not only that the visual details are missing, but the whole autobiographical memory seems to be deficient in a way.

Chris - And if you compare how strongly the different parts of the brain are being activated in the two groups, because if they're trying harder to try to recall memories because something's amiss, you might see a disparity. So how does the activation that you do see compare between the two groups?

Cornelia - Exactly. So we found that the visual perceptual cortex or the occipital cortex actually had more activation for people with aphantasia than for our control participants. And the hippocampus, on the other side, had less activation in people with aphantasia than in controls. And we thought that the hippocampus is impacted because the entire memories are deficient. It's not only the visual part, but also the global autobiographical memory. And for the visual cortex, at first we were a bit surprised about that because we thought maybe because they don't have the images, also the visual perceptual cortex would also have less activation. But it's actually known in the literature that the visual perceptual cortex has more activation in aphantasia. And this may be a cause of aphantasia. There are theories that the visual cortex has too much activation in aphantasia and all the small signals that you need to see mental images in your mind's eye, which are not so stark as the outside world don't exceed the activation in the visual cortex.

Chris - It's almost like not being able to see the wood for the trees: you've got so much noise going on that you end up recruiting a whole noisy milieu of messages, which, effectively, confuses the experience. So you don't actually form a coherent mental image?

Cornelia - Exactly. That's what we think. We don't know for sure yet, but that's how we interpreted our results.

Chris - Fascinating. What happens then if you do the same study on people blind since birth?

Cornelia - Also very interesting question because we are just acquiring those data and we haven't analysed the data yet, so I don't know yet. But it's a fascinating research question!

Chris - There has to be something more to this though, doesn't there? Because people who have been blind since birth have excellent memories. So it's not just a question of being able to see things that make you very good at remembering things, is the message that I would take away from that?

Cornelia - That's what I think too, although there's very, very little research on this done with like state of the art autobiographic memory interviews and also MRIs. So that's why we are doing this kind of more rigorous study and experiment to see how they compare with sighted people, right. Maybe, maybe their memory just works differently because, I agree, if you're blind, you have to have a good memory because otherwise if you put your cup of coffee somewhere else and you can't remember where you put it, you don't see it, right, so you have to have this memory to relying on finding your object in your environment again.