How to forget unwanted memories

Everyone has memories they would rather forget, and they may know the triggers that bring them bouncing back. Bad memories can underlie a number of problems, from post-traumatic stress disorder to phobias.

When an unwanted memory intrudes on the mind, it is a natural human reaction to want to block it out.

A hundred years ago, Freud suggested that humans have a mechanism that they can use to block unwanted memories out of consciousness.

More recently, scientists have started to understand how this works.

Neuroimaging studies have observed which brain systems play a part in deliberate forgetting, and studies have shown that it is possible for people deliberately to block memories from consciousness.

How do memories form?

For a person's mind to store a memory, proteins stimulate the brains cells to grow and form new connections.

The more we dwell on a memory or rehearse the specific events surrounding the memory, the stronger these neuronal connections become.

The memory remains there as long as we revisit it from time to time.

For a long time, people thought that the older the memory, the more fixed it is, but this is not necessarily true.

Each time we revisit a memory, it becomes flexible again. The connections appear to become malleable, and then they reset. The memory can change a little each time we recall it, and it resets stronger and more vividly with every recall.

Even long-term memories are not stable.

This process of strengthening is called reconsolidation. Reconsolidation can change our memories slightly for better or for worse. Manipulating this process can do the same.

If something frightens us when we are young, the memory of that event can become a little more frightening each time we recall it, leading to a fear that may be out of proportion with the real event.

A small spider that frightened us once may get bigger in our minds over time. A phobia can result.

In contrast, casting a humorous light on an embarrassing memory, for example, by weaving it into a funny story, can mean that in time, it loses its power to embarrass. A social gaff can become a party piece.

Why are bad memories so vivid?

Many people find that bad experiences stand out in the memory more than good ones. They intrude on our consciousness when we do not want them to.

Researchers have shown that bad memories really are more vivid than good ones, possibly due to the interaction between the emotions and the memories. This is particularly so when the emotions and memories are negative.

Neuroimaging has shown scientists that the process of encoding and retrieving bad memories involves the parts of the brain that process emotions, specifically the amygdala and the orbitofrontal cortex.

It seems the stronger the emotions associated with the memory, the more detail we will recall.

fMRI studies reveal greater cellular activity in these regions when someone is going through a bad experience.

Substituting memories

In 2012, scientists at the University of Cambridge showed for the first time which brain mechanisms are involved in substituting and suppressing memories.

They found that a person can suppress a memory, or force it out of awareness, by using a part of the brain, known as the dorsolateral prefrontal cortex, to inhibit activity in the hippocampus. The hippocampus plays a key role in remembering events.

To substitute a memory, people can redirect their consciousness towards an alternative memory.

They can do this by using two regions called the caudal prefrontal cortex and the mid-ventrolateral prefrontal cortex. These areas are important for bringing specific memories into the conscious mind, in the presence of distracting memories.

Suppressing a memory involves shutting down parts of the brain that are involved in recall. To substitute a memory, those same regions must be actively engaged in redirecting the memory way towards a more attractive target.

One of the report's authors, Dr. Michael Anderson, likens this to either slamming on the brakes in a car or steering to avoid a hazard.

The researchers used functional magnetic resonance imaging (fMRI) to observe the brain activity of participants during an activity.

This activity involved learning associations between pairs of words, and then trying to forget the memories by either recalling alternative ones to substitute them or blocking them out.

Results showed that both strategies are equally effective, but that different neural circuits are activated.

In post-traumatic stress disorder (PTSD), people who have experienced a traumatic life event are troubled by unwanted memories that insist on intruding into the consciousness.

Knowing more about how a memory can be substituted or suppressed might help people with this debilitating condition.

Source: Medical News Today