How the brain consolidates information while you rest

Health and Wellness 13. jul 2021 3 min Associate professor Diego Vidaurre Henche Written by Kristian Sjøgren

Researchers have identified a signal in the brain that appears to play an important role when the brain consolidates new information into memory so that the information can be more easily retrieved later.

The brain is an incomparable machine capable of performing absolutely amazing things.

For example, memory is the result of a combination of electrical charges and anatomical imprints, which enable you to evoke your childhood memories or the road home from the city after a pub crawl.

For many years, researchers have studied how our brains at rest spontaneously replay recently acquired information to consolidate it in memory, but how this process is orchestrated is an open question.

Now, researchers in the United Kingdom and Denmark have made a discovery that can help explain what happens in the brain when information is consolidated so that it can always be retrieved.

“In our study, we link two signals in the brain. One is related to subconscious consolidation of memory and the other to attention and cognition. Our discovery is useful because this type of memory consolidation is known to be preserved across all animals, and because errors in the same mechanisms are likely to play important roles in various brain disorders, including stroke and Alzheimer’s disease,” explains a researcher behind the new study, Diego Vidaurre Henche, Associate Professor, Department of Clinical Medicine, Aarhus University.

The research has been published in Neuron.

Memory needs to consolidate information

The brain is marvellous and excels at storing complicated information.

This applies if you want to learn to play classical music on the piano or find your way around a new city.

When the brain stores new information, it must first learn this information. The brain does this when you play music from a score or walk in the city for the first time. What you learn is therefore stored anatomically.

However, what you learn must also be consolidated in your memory, so that you do not have to actively remember all the notes in the music or the route through the city.

The brain consolidates the new information to store the information in the subconscious.

In the example of the walk in a new city, this might happen later when sitting down at a café – or when you sleep. When the brain is no longer actively engaged in learning, the information can be rapidly processed and consolidated.

“When you then sit down and relax, the brain rapidly repeats the neural sequence that was built up while walking, and eventually sends it to the cerebral cortex for final consolidation. The hippocampus is critically involved in this process, which researchers call signal replay. In experiments with mice and rats, we can find this signal in their brains as they subconsciously recapitulate what they learned,” says Diego Vidaurre Henche.

Examined brain signals while trial participants rested

The researchers studied replay in more detail among participants who were asked to learn and remember a sequence of items from pictures they were shown.

The participants wore helmets that monitored the electrical activity in their brains.

The researchers studied the electrical activity of the brain when the participants actively tried to remember the images but also when they thought about other things.

The researchers used advanced statistical methods to identify signals related to consolidation.

“In a previous study, we identified signals in the brain that are likely related to paying less attention to the outside environment and more to our own thoughts. In this study, we went a step further and linked the replay signal to this “reflective” signal in the brain,” explains Diego Vidaurre Henche.

Associated with “doing nothing”

The second signal in the brain is the electrophysiological signature from the default mode network (DMN).

Although it has been traditionally associated with “doing nothing”, the DMN is the signal the brain activates when we think or do something inside our heads. Conversely, this signal goes away when pay attention to the external world. An increase of the DMN signal can therefore be linked to the activity of the brain when we think about nothing in particular and disappear into an inner world.

Researchers have for many years studied the DMN and its signal.

“For example, we know that disruptions of the DMN are linked to mental disorders. So far, however, many aspects about this network and its significance remain enigmatic,” says Diego Vidaurre Henche.

The default mode network is not simply a default setting

The evidence indicates that replay depends on the DMN.

The researchers analysed the brain scans and found that the DMN becomes more active when replay takes place.

This is the first time that researchers have discovered the link that substantiates that the DMN is related to inner attention and consolidating memories.

“Our discovery means that we should probably stop thinking of the DMN as the brain’s default setting, which is initiated when nothing else happens. Our study suggests that DNM coordinates replay so that the replay signal does not conflict with ongoing cognition,” concludes Diego Vidaurre Henche.

Replay bursts coincide with activation of the default mode and parietal alpha network” has been published in Neuron. In 2019, the Novo Nordisk Foundation awarded a grant to Diego Vidaurre Henche for the project Disambiguating the Neural Threads of Perception and Cognition to Characterise Individual Behaviour.

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