A special brain mechanism has been discovered that stores stress-related, unconscious memories.

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 This is what eurekalert.org writes today in a news release.

Unavailable trauma-related memories

At first glance, some memories may seem as if they do not exist. We are talking about unconscious memories, where it is often assumed that the person protects himself against the emotional pain that it would mean to remember these events.





Some stressful experiences - such as chronic abuse in childhood - are so overwhelming and traumatic that the memories can become like a shadow hiding in the brain, writes Eurekalert.

But the repressed memories can cause mental problems such as anxiety, depression, post-traumatic stress disorder or dissociative disorders. 





Eurekalert refers here to a specific cognitive process, called state-dependent learning, which can contribute to some memories becoming inaccessible to the normal consciousness. These are memories that are formed in the context of a special mood or emotional state, and which can thus best be recalled when the brain is in a similar state.

 

The brain's different radio frequencies

In a new study done on mice, researchers have discovered a mechanism in the brain that may help explain why trauma-related memories can be stored as unconscious in the brain - and how they can be recovered.

While the neurotransmitter glutamate is claimed to be particularly effective in storing normal memories, the researchers believe that another neurotransmitter in the brain, extra-synaptic GABA, has a special role in storing fear-related memories - and that this system makes memory inaccessible or unconscious for consciousness.

Professor Jelena Radulovic uses the following metaphor to explain what they have actually found:

The brain works differently in different states, much like a radio works completely differently depending on whether it is set to AM or FM frequency.

It is as if the brain in its normal state is set to FM frequency to access ordinary memories, but that it must be set to AM frequency to access unconscious memories.

In response to traumatic stress, instead of activating the glutamate system to store memories, some individuals will activate the extra synaptic GABA system and thus form inaccessible traumatic memories, Eurekalert continues.

 

Retrieved fear-related memories

In the new study, the researchers did an experiment in which they added a chemical to the mice, gaboxadol, which stimulates extra-synaptic GABA receptors.

It's like we got them a little drunk, just enough to change their brain state, Radulovic says.

In the experiment, the mice were placed in a box and given a short electric shock. When the mice returned to the box the next day, there was no indication that they remembered this shock. They moved around freely without seeming to be afraid of another shock. 

However, when they were given some of the drug gaboxadol, everything changed. The mice froze in terror, and it was clear that they were expecting another shock.

The researchers interpret the findings as follows: When the mice were now chemically brought back into the same state of consciousness as when they were shocked, they could also remember the fear-creating event.

They point out that there are some fundamental differences between storing memories in the normal way, where the neurotransmitter glutamate is central and where the memories are made in networks of the brain that include the cortex (thinking brain), and between storing memories in an unconscious way, where the neurotransmitter extra-synaptic GABA is central and where the memories are stored in sub-cortical networks, ie in networks that are not accessible to the normal consciousness.

 

May be important for future treatment of mental disorders

In short, in this study it was possible through the use of the drug gaboxadol to activate such a state of consciousness that the fear-related, unconscious memories could be made consciously available.

Professor Radulovic says that the study may be relevant for future treatment of some forms of mental disorders. She says that it can be difficult for therapists to help patients with the traumatic experiences that are the cause of their symptoms, but where the patients do not remember these experiences.

The best way to access the memories in the unconscious system is to return the brain to the same state of consciousness as when the memory was encoded, the study showed according to Eurekalert.org.

Eurekalert writes:

The findings show that there are several paths for storing fear-related memories, and we have identified one such path, says Professor Jelena Radulovic. 

This may in the long run lead to new treatment methods for patients with mental disorders in those cases where access to traumatic memories is necessary if they are to recover.

 

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