How are memories stored in the brain

Memory: How memory stores what has been experienced

Every day our senses are fired with thousands of new impressions. Why do we remember some forever and immediately forget others? We are on the trail of memories

If people couldn't remember anything, they wouldn't know anything. If people could remember everything, they would know everything - but it would be of no use to them. Our memory is a central part of our being, so we humans have always given our memories a lot of thought.

As early as the fourth century before the year zero, Plato located memories at the core of our human existence: the soul. There, according to the Greek philosopher, our memories were expressed in wax tablets. We do not remember what is not pressed onto these inner wax tablets.

"If someone's wax is heavily applied in the soul and is plentifully and smoothly and properly softened," wrote Plato, the "drawn impressions, since they are pure and have sufficient depth, are also permanent." Such people are also "docile, then too." of good memory, furthermore they do not confuse impressions of the perceptions, but always present correctly. "

Where is a reminder saved? What is the memory?

Even then, the Greek philosopher asked exactly the questions that cognitive researchers, psychologists and neurologists are still concerned with today:

  • How does a person form a memory?
  • Why do we forget some things and remember others?
  • Which memories are real, which are falsified?
  • And how do we falsify them?

Science today is further than Plato would ever have dreamed of more than 2000 years ago. She can differentiate between short-term memory and long-term memory. We know that over 100 billion brain cells conduct information through our head, impressions are stored in neural connections and even changed when we call them up.

And yet: how can we imagine it now, the place where all the impressions of our lives are stored?

It is difficult to grasp our memory in its entirety. Our memory is abstract, depending on the culture and epoch people have differently imagined how our thoughts, feelings and impressions are stored - and where.

It was primarily the invention of the printing press that shaped this Image of our memory as a librarythat you might even be able to do yourself. If you are looking for information and know that you have already learned it, you would only have to rummage through the musty shelves in your own brain, maybe wipe the dust off the back of the heavy volumes that you put there at some point Has. The right book has to be somewhere if you just look in the right place.

Of course, in this imagined library of one's own past, there is not only the language that has been put on paper, but also Photographs - at least since the camera was invented. Sound recordings and video snippets can also be found there.

Since the Invention of the computer Electronic technology dominates our ideas of human memory: Our memory image is accordingly a code made up of ones and zeros, stored temporarily on memory, long-term on hard drives.

But can that really be everything?

What determines our memory? What skills does memory need?

Perhaps the question of a generally valid structure, a metaphor for our memory is the wrong one. Perhaps it is rather the functioning of our memories that we can approach. This is exactly what large parts of today's research do.

So what happens from a neurological perspective with information that we store in our memory - however we like to imagine it?

Every time the human brain processes information, it changes a little. It links nerve cells in a new or different way, while still spinning on what is known as neural network. Every time we learn something, this network becomes larger and denser - by the way, it has a unique structure for every person.

If such new connections are formed between nerve cells and entire brain areas - for example when we learn a new instrument - science speaks of neuroplasticity. Neurogenesis, on the other hand, is used when nerve cells form anew, also as an adaptation to our environment and the impressions that we collect from it.

So first man becomes one of the most adaptable beings on earth, through this interaction: Our brain determines how we can react to our environment - at the same time, our environment shapes our brain.

Why do we remember some experiences and forget other experiences?

The fact that our brain is not constantly overloaded in the process borders on a miracle of nature. Because it is constantly active, as it has to filter, process and store sensory impressions in every moment of our life. Filtering is particularly important here.

Experiences remain in the so-called for just a few seconds Ultra-short-term memoryIf you do not assign any further importance to them, the impression is immediately discarded. This happens with information that we do not focus on, that takes place in our periphery. We immediately forgot whether the house we were driving past was red or dark purple.

However, if we concentrate on impressions - if we want to memorize a series of numbers or hear new words in a foreign language for the first time - then we try to use this information in the Short term memory to save. This works in a similar way to the main memory of a computer: It has to be cleared regularly in order to be able to take in new information. The current state of research assumes that we can keep information in this human working memory for about twenty minutes - then these neural connections are deleted again.

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But this does not happen completely. This is another reason why it makes sense to take a short break after twenty minutes when learning vocabulary, for example, and then repeat what you have learned - in the hope that it will work out in the Long-term memory sets.

There is no central place in our brain where we store all information. The different types of memories are stored in different areas: Scientists locate neural connections that are related to skills learned in the Striatum. Factual knowledge is more likely to be in Hippocampus stored, emotions in the brain region Amygdala.

Why do we sometimes remember wrongly? Can our past be manipulated?

But suppose we have managed to consolidate some memories, to link enough nerve cells tightly enough: How do we call them up again? And why do we remember some things better, others worse?

In order to approach these questions, it is helpful to fall back on a categorization of science. We save motion sequences in the procedural memory. We remember them almost automatically when we have repeated the movement enough times. Lionel Messi doesn't have to think twice about his magic tricks on the ball; neither does the pianist Igor Levit when he strikes the keys of a piano.

If we want to call up knowledge that we have acquired, we access it semantic memory back, for example, when trying to remember what we learned in history class at school.

Our perceptual memory we need if we want to remember certain patterns. For example, we can recognize an old friend by her facial features, even though she has changed a lot. Or the melody of a familiar song, although it is played in a different pitch or with different instruments.

The episodic memory is our own personal autobiography. We write these ourselves consciously and unconsciously, but never objectively and factually. On the contrary: we impose our own narratives on our past.

In her autobiographical work “What never happened”, the writer Nadja Spiegelman describes it as follows: “Physiologically, it makes no difference whether you experience something or imagine it. It is for this reason that we are constantly telling stories, for this reason each culture has its own myths. We don't see things as they are, we see them as we understand them. [...] We set the boundaries between truth and fiction ourselves, and the better we have our fiction under control, the better we have our reality under control. "

Amnesia: Why do we forget some things completely?

In addition, the experiences from some phases of life stick particularly strongly, others less so. This is very individual, but this intensity of memory almost always follows the same pattern, the so-called Memory curve: While we hardly remember our early childhood, youth, especially the period between the ages of 15 and 25, seems to be the most intense; the middle years are less present. However, we usually remember the last few years before the present very clearly, these impressions are comparatively “fresh”.

So-called reminiscence humps, i.e. the ones, are particularly exciting Teenage years. Alzheimer's patients usually remember that time of growing up particularly well - because this is where large parts of our identity are formed, scientists suspect.

How we perceive our past does not only depend on how we store certain impressions. Our memory image is subject to constant change. Every time we call up these memories, we may alter and falsify their content. They can replace, change or superimpose similarly stored memories. For example, we may perceive certain childhood memorabilia differently when we read a novel today that tells the story of a fictional character's childhood.

But it also works the other way around. If we do not recall a memory for a long time, it fades and the connection between the decisive neurons becomes weaker. So it is becoming more and more difficult for us to call up these impressions.

So what is our memory now? Plato's wax tablet, a library, an internal hard drive? Are these just bad metaphors for neuronal processes, for neurons that are constantly re-linked?

It is probably the same as always: the truth lies somewhere between all approaches in cognitive research, psychology or philosophy - if it exists at all. Of course, a memory can be understood as purely that which can be measured in our brain waves. But does it do justice to the real, material events that these memories once were? Whether our memory can really be reduced to this cannot be definitively clarified.

Even the thoughts of the philosopher Walter Benjamin cannot do that. However, they encourage thought about what is most likely to do justice to the sublimity of such a complex and fluid subject as human memory: “Language has unmistakably meant that memory is not an instrument for exploring the past, but rather the medium . "