How does the brain lock thoughts in memory

"Our memory is not made for the past, but for the future"

Forgetting is by no means just a weakness, it is often an elaborate, active process. Roland Benoit has been researching in his new research group since the beginning of May how memories can be deliberately erased, and how episodes from the past can serve us to function in the future Adaptive memory.

We constantly try not to forget anything - be it the mother's birthday, the next doctor's appointment or the essentials from politics and society. We also look at old age with concern because we fear we will become more forgetful. Forgetting has a bad reputation.

It is by no means just a weakness or a sign of declining brain performance. Rather, it is often an active process that is associated with a lot of effort - especially when the memory is overpowering and has even developed into trauma.

But how exactly does it work to intentionally forget? Roland Benoit has been addressing this question since the beginning of May as head of the newly founded research group for Adaptive memory at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig. He is not only interested in how unwanted memories can be suppressed, but also how we use episodes from the past to simulate our future. A conversation about forgetting and remembering, the past and the future.

Mr. Benoit, in our everyday life we ​​use appointment planners and memos to avoid forgetting as much as possible. Instead, they explore how we intentionally forget. Why?

Because our memory is a fantastic evolutionary development through which we can use memories of positive and negative experiences, for example, to make good decisions for the future. Still, remembering all the negative things that have happened to you is certainly not helpful. This is particularly evident in people who suffer from spontaneous, unwanted memories of traumatic experiences. In general, however, we also experience many experiences in our everyday life, the memories of which we would like to forego.

Can you give me an example?

Imagine you had an argument with your partner. The next time you see your partner, you will remember it again, even though you want to check it off and look ahead. In such a situation, where we are motivated not to remember a previous experience, it seems possible to suppress emerging memories and eventually to forget them. I want to find out exactly how this works. In principle, there seem to be two mechanisms for actively deleting memories from our memory.

What do they look like?

Imagine that you are sitting in a car that is automatically heading for the unwanted memory content at high speed. You can now avoid the clash with the unwanted memory in two ways:
On the one hand, by stepping heavily on the mental brakes and trying to stop the memory process in time - i.e. by direct suppression. Two brain structures are crucial for this. One of them is the hippocampus, which, like a kind of motor, drives us to complete, unwanted memory if it weren't for the second crucial structure: the prefrontal cortex in the foremost area of ​​the brain. A part of the right prefrontal cortex seems to act as a brake that switches off the hippocampus - and with it memory - to some extent.

And the second kind of deliberate forgetting, how does it work?

Instead of stepping on the mental brakes so as not to race towards the unwanted memory, you can also try to avoid it and approach another memory. For example, when you see your partner again, instead of the argument, you can think of that nice dinner with him at the Italian restaurant. The alternative memory blocks access to the unwanted memory content. So here you do not stop any memory, but specifically influence the memory process in order to drive the thoughts of another past event. With this substitute remembering, the hippocampus is not slowed down, but used in a targeted manner. Parts of the left prefrontal cortex serve as a kind of steering wheel that steers the hippocampus and thus the memory process in the right direction.
These two mechanisms of active forgetting, direct suppression and substitute remembering, can therefore continuously help us to maintain control over our memories. In patients with post-traumatic stress disorder, however, these seem to be impaired.

When is which of the two mechanisms used?

That is currently an open question. I think that if you have particularly strong memories, it may be easier to replace them with another memory than to stop the process of remembering completely. But whether this is also the more effective mechanism for getting memories under control over the long term is one of the many questions that my research group will continue to investigate.

What then happens to our unwanted memories? Are they actually erased from our memory or do they only get into the "back room", into the unconscious? So is there really a real forgetting of previously anchored memories?

In fact, both seem possible. If you've always successfully thought of going to a restaurant with your partner instead of the argument, this happy memory can simply become a lot stronger. In this case, it may just block access to the unwanted memory.
We and other researchers have also shown that both mechanisms can actually lead to the memory itself being forgotten. In this case, you would no longer be able to remember certain details of the dispute, even if we asked you about it directly. Such suppressed memories then no longer seem to be able to unconsciously influence our behavior.

So these repression mechanisms only work if we consciously choose to do so?

No, probably not only. The research of my working group focuses on conscious, deliberate forgetting. However, I suspect that we unconsciously use the same processes in everyday life. For example, if we want to get rid of the memory of an embarrassing situation, a suppression mechanism is often unconsciously in place.

Does intentional forgetting only play a role in the context of negative events?

No, not that either. For example, we often simply have very similar information stored in our memory. For example, if you want to remember your new phone number, you may only be able to think of the well-known old one. In these situations we seem to use a similar mechanism to specifically weaken the stronger memory of the old number and thus be able to retrieve the new one.

In your new research group, you will not only investigate how we can erase or rewrite memories, but also how they will help us function in the future. You have to explain that to us in more detail.

Basically, our memory is not made for the past, but for the future. You shouldn't think of it as something passive like a video on which I can watch exactly what happened. Rather, we mostly only remember individual parts of our experiences and unconsciously fill in the gaps with our general knowledge. So remembering is a constructive process. Our ability to imagine the future is based precisely on this constructive memory. For example, what would it be like to have dinner with a certain person in a certain restaurant? In order to imagine this situation, we can link memories of the restaurant with those of the person in order to imagine completely new experiences and decide whether we really want to join in this Person in this Want to meet restaurant.

What exactly do you want to find out in this area, constructive memory?

On the one hand, I'm interested in how our brain is able to simulate the future. We already know that the same brain regions are active here that are also used during remembering. However, we do not yet understand which region has which role. On the one hand, I am interested in the function of the so-called medial prefrontal cortex, which probably helps us predict how emotionally we would react to certain events.
On the other hand, I would like to know why it is even important to imagine the future with the help of memories. On the one hand, it allows us to make more far-sighted decisions. On the other hand, it is not always advantageous to constantly imagine the future.

What do you mean?

If, for example, we are afraid of certain situations in the future, such future simulations could further intensify the fears and make them appear even more plausible. In these moments, it could be better not to keep playing through the future, but to interrupt these thoughts. Here I would like to examine in more detail whether we also use mechanisms of displacement to stop our future simulations.

So do you advocate appreciating forgetting more?

Yes! However, I do not want to call with my research to simply forget all bad experiences in his life. Often it is precisely the difficult moments in life that we have to integrate into our self-image and that ultimately make us a good part. However, again, it is not healthy to always remember everything bad that has ever happened to you or that could happen in the future.

Thank you for talking to us, Mr Benoit.

The interview was conducted by Verena Müller, science editor at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig.