̽��ֱ�� of Cambridge - Michael Anderson

Suppressing negative thoughts may be good for mental health after all

cjb250 — Wed, 20 Sep 2023 18:00:39 +0000

Researchers at the Medical Research Council (MRC) Cognition and Brain Sciences Unit trained 120 volunteers worldwide to suppress thoughts about negative events that worried them, and found that not only did these become less vivid, but that the participants’ mental health also improved.

“We’re all familiar with the Freudian idea that if we suppress our feelings or thoughts, then these thoughts remain in our unconscious, influencing our behaviour and wellbeing perniciously,” said Professor Michael Anderson.

“ ̽��ֱ��whole point of psychotherapy is to dredge up these thoughts so one can deal with them and rob them of their power. In more recent years, we’ve been told that suppressing thoughts is intrinsically ineffective and that it actually causes people to think the thought more – it’s the classic idea of ‘Don’t think about a pink elephant’."

These ideas have become dogma in the clinical treatment realm, said Anderson, with national guidelines talking about thought avoidance as a major maladaptive coping behaviour to be eliminated and overcome in depression, anxiety, PTSD, for example.

When COVID-19 appeared in 2020, like many researchers, Professor Anderson wanted to see how his own research could be used to help people through the pandemic. His interest lay in a brain mechanism known as inhibitory control – the ability to override our reflexive responses – and how it might be applied to memory retrieval, and in particular to stopping the retrieval of negative thoughts when confronted with potent reminders to them.

Dr Zulkayda Mamat – at the time a PhD student in Professor Anderson’s lab and at Trinity College, Cambridge – believed that inhibitory control was critical in overcoming trauma in experiences occurring to herself and many others she has encountered in life. She had wanted to investigate whether this was an innate ability or something that was learnt – and hence could be taught.

Dr Mamat said: “Because of the pandemic, we were seeing a need in the community to help people cope with surging anxiety. There was already a mental health crisis, a hidden epidemic of mental health problems, and this was getting worse. So with that backdrop, we decided to see if we could help people cope better.”

Professor Anderson and Dr Mamat recruited 120 people across 16 countries to test whether it might in fact be possible – and beneficial – for people to practice suppressing their fearful thoughts. Their findings are published today in Science Advances.

In the study, each participant was asked to think of a number of scenarios that might plausibly occur in their lives over the next two years – 20 negative ‘fears and worries’ that they were afraid might happen, 20 positive ‘hopes and dreams’, and 36 routine and mundane neutral events. ̽��ֱ��fears had to be worries of current concern to them, that have repeatedly intruded in their thoughts.

Each event had to be specific to them and something they had vividly imagined occurring. For each scenario, they were to provide a cue word (an obvious reminder that could be used to evoke the event during training) and a key detail (a single word expressing a central event detail). For example:

Negative – visiting one’s parents at the hospital as a result of COVID-19, with the cue ‘Hospital’ and the detail ‘Breathing’.
Neutral – a visit to the opticians, with the cue ‘Optician’ and the detail ‘Cambridge’.
Positive – seeing one’s sister get married, with the cue ‘Wedding’ and the detail ‘Dress’.

Participants were asked to rate each event on a number of points: vividness, likelihood of occurrence, distance in the future, level of anxiety about the event (or level of joy for positive events), frequency of thought, degree of current concern, long-term impact, and emotional intensity.

Participants also completed questionnaires to assess their mental health, though no one was excluded, allowing the researchers to look at a broad range of participants, including many with serious depression, anxiety, and pandemic-related post-traumatic stress.

Then, over Zoom, Dr Mamat took each participant through the 20-minute training, which involved 12 ‘No-imagine’ and 12 ‘Imagine’ repetitions for events, each day for three days.

For No-imagine trials, participants were given one of their cue words, asked to first acknowledge the event in their mind. Then, while continuing to stare directly at the reminder cue, they were asked to stop thinking about the event – they should not try to imagine the event itself or use diversionary thoughts to distract themselves, but rather should try to block any images or thoughts that the reminder might evoke. For this part of the trial, one group of participants was given their negative events to suppress and the other given their neutral ones.

For Imagine trials, participants were given a cue word and asked to imagine the event as vividly as possible, thinking what it would be like and imagining how they would feel at the event. For ethical reasons, no participant was given a negative event to imagine, but only positive or neutral ones.

At the end of the third day and again three months later, participants were once again asked to rate each event on vividness, level of anxiety, emotional intensity, etc., and completed questionnaires to assess changes in depression, anxiety, worry, affect, and wellbeing, key facets of mental health.

Dr Mamat said: “It was very clear that those events that participants practiced suppressing were less vivid, less emotionally anxiety-inducing, than the other events and that overall, participants improved in terms of their mental health. But we saw the biggest effect among those participants who were given practice at suppressing fearful, rather than neutral, thoughts.”

Following training – both immediately and after three months – participants reported that suppressed events were less vivid and less fearful. They also found themselves thinking about these events less.

Suppressing thoughts even improved mental health amongst participants with likely post-traumatic stress disorder. Among participants with post-traumatic stress who suppressed negative thoughts, their negative mental health indices scores fell on average by 16% (compared to a 5% fall for similar participants suppressing neutral events), whereas positive mental health indices scores increased by almost 10% (compared to a 1% fall in the second group).

In general, people with worse mental health symptoms at the outset of the study improved more after suppression training, but only if they suppressed their fears. This finding directly contradicts the notion that suppression is a maladaptive coping process.

Suppressing negative thoughts did not lead to a ‘rebound’, where a participant recalled these events more vividly. Only one person out of 120 showed higher detail recall for suppressed items post-training, and just six of the 61 participants that suppressed fears reported increased vividness for No-Imagine items post-training, but this was in line with the baseline rate of vividness increases that occurred for events that were not suppressed at all.

“What we found runs counter to the accepted narrative,” said Professor Anderson. “Although more work will be needed to confirm the findings, it seems like it is possible and could even be potentially beneficial to actively suppress our fearful thoughts.”

Although participants were not asked to continue practising the technique, many of them chose to do so spontaneously. When Dr Mamat contacted the participants after three months, she found that the benefits in terms of reduced levels of depression and negative emotions, continued for all participants, but were most pronounced among those participants who continued to use the technique in their daily lives.

“ ̽��ֱ��follow up was my favourite time of my entire PhD, because every day was just joyful,” she said. “I didn’t have a single participant who told me ‘Oh, I feel bad’ or ‘This was useless’. I didn't prompt them or ask ‘Did you find this helpful?’ They were just automatically telling me how helpful they found it.”

One participant was so impressed by the technique that she taught her daughter and her own mother how to do it. Another reported how she had moved home just prior to COVID-19 and so felt very isolated during the pandemic.

“She said this study had come exactly at the time she needed it because she was having all these negative thoughts, all these worries and anxiety about the future, and this really, really helped her,” said Dr Mamat. “My heart literally just melted, I could feel goosebumps all over me. I said to her ‘If everyone else hated this experiment, I would not care because of how much this benefited you!’.”

̽��ֱ��research was funded by the Medical Research Council and the Mind Science Foundation.

Reference
Mamat, Z, and Anderson, MC. Improving Mental Health by Training the Suppression of Unwanted Thoughts. Sci Adv; 20 Sept 2023; DOI: 10.1126/sciadv.adh5292

̽��ֱ��commonly-held belief that attempting to suppress negative thoughts is bad for our mental health could be wrong, a new study from scientists at the ̽��ֱ�� of Cambridge suggests.

What we found runs counter to the accepted narrative

Michael Anderson

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Women enjoying sun

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Selective amnesia: how rats and humans are able to actively forget distracting memories

cjb250 — Wed, 07 Nov 2018 09:45:20 +0000

̽��ֱ��human brain is estimated to include some 86 billion neurons (or nerve cells) and as many as 150 trillion synaptic connections, making it a powerful machine for processing and storing memories. We need to retrieve these memories to help us carry out our daily tasks, whether remembering where we left the car in the supermarket car park or recalling the name of someone we meet in the street. But the sheer scale of the experiences people could store in memory over our lives creates the risk of being overwhelmed with information. When we come out of the supermarket and think about where we left the car, for example, we only need to recall where we parked the car today, rather than being distracted by recalling every single time we came to do our shopping.

Previous work by Professor Michael Anderson at the Medical Research Council Cognition and Brain Sciences Unit, ̽��ֱ�� of Cambridge, showed that humans possess the ability to actively forget distracting memories, and that retrieval plays a crucial role in this process. His group has shown how intentional recall of a past memory is more than simply reawakening it; it actually leads us to forget other competing experiences that interfere with retrieval of the memory we seek.

“Quite simply, the very act of remembering is a major reason why we forget, shaping our memory according to how it is used,” says Professor Anderson.

“People are used to thinking of forgetting as something passive. Our research reveals that people are more engaged than they realise in actively shaping what they remember of their lives. ̽��ֱ��idea that the very act of remembering can cause forgetting is surprising and could tell us more about people’s capacity for selective amnesia.”

While this process improves the efficiency of memory, it can sometimes lead to problems. If the police interview a witness to a crime, for example, their repeated questioning about selected details might lead the witness to forget information that could later prove important.

Although the ability to actively forget has been seen in humans, it is unclear whether it occurs in other species. Could this ability be unique to our species, or at least to more intelligent mammals such as monkeys and great apes?

In a study published today in the journal Nature Communications, Professor Anderson together with Pedro Bekinschtein and Noelia Weisstaub of Universidad Favaloro in Argentina, has shown that the ability to actively forget is not a peculiarly human characteristic: rats, too, share our capacity for selective forgetting and use a very similar brain mechanism, suggesting this is an ability shared among mammals.

To demonstrate this, the researchers devised an ingeniously simple task based on rats’ innate sense of curiosity: when put into an environment, rats actively explore to learn more about it. When exploring an environment, rats form memories of any new objects they find and investigate.

Building on this simple observation, the researchers allowed rats to explore two previously-unseen objects (A and B) in an open arena – the objects included a ball, a cup, small toys, or a soup can. Rats first got to explore object A for five minutes, and then were removed from the arena; they were then placed back in the arena 20 minutes later with object B, which they also explored for five minutes.

To see whether rats showed retrieval-induced forgetting, like humans, rats next performed “retrieval practice” on one of the two objects (e.g. A) to see how this affected their later memory for the competitor object (B). During this retrieval practice phase, the researchers repeatedly placed the rat in the arena with the object they wanted the rat to remember (e.g. A), together with another object never seen in the context of the arena. Rats instinctively prefer exploring novel objects, and so on these “retrieval practice” trials, the rats clearly preferred to explore the new objects, implying that they indeed had remembered A and saw it as “old news”.

To find out how repeatedly retrieving A affected rats’ later memory for B, in a final phase conducted 30 minutes later, the researchers placed the rat into the arena with B and an entirely new object. Strikingly, on this final test, the rats explored both B and the new object equally – by selectively remembering their experience with A over and over, rats had actively trained themselves to forget B.

In contrast, in control conditions in which the researchers skipped the retrieval practice phase and replaced it with an equal amount of relaxing time in the rats’ home cage, or an alternative memory storage task not involving retrieval, rats showed excellent memory for B.

Professor Anderson’s team then identified an area towards the front of the rat’s brain that controls this active forgetting mechanism. When a region at the front of the rat’s brain known as the medial prefrontal cortex was temporarily ‘switched off’ using the drug muscimol, the animal entirely lost its ability to selectively forget competing memories; despite undergoing the same “retrieval practice” task as before, rats now recognised B. In humans, the ability to selectively forget in this manner involves engaging an analogous region in the prefrontal cortex.

“Rats appear to have the same active forgetting ability as humans do – they forget memories selectively when those memories cause distraction,” says Professor Anderson. “And, crucially, they use a similar prefrontal control mechanism as we do. This discovery suggests that this ability to actively forget less useful memories may have evolved far back on the ‘Tree of Life’, perhaps as far back as our common ancestor with rodents some 100 million years ago.”

Professor Anderson says that now that we know that the brain mechanisms for this process are similar in rats and humans, it should be possible to study this adaptive forgetting phenomenon at a cellular – or even molecular – level. A better understanding of the biological foundations of these mechanisms may help researchers develop improved treatments to help people forget traumatic events.

̽��ֱ��research was funded by the Medical Research Council, the National Agency of Scientific and Technological Promotion of Argentina and the International Brain Research Organization.

Reference
Bekinschtein, B, et al. A Retrieval-Specific Mechanism of Adaptive Forgetting in the Mammalian Brain. Nature Comms; 7 Nov 2019; DOI: 10.1038/s41467-018-07128-7

Our ability to selectively forget distracting memories is shared with other mammals, suggests new research from the ̽��ֱ�� of Cambridge. ̽��ֱ��discovery that rats and humans share a common active forgetting ability – and in similar brain regions – suggests that the capacity to forget plays a vital role in adapting mammalian species to their environments, and that its evolution may date back at least to the time of our common ancestor.

Quite simply, the very act of remembering is a major reason why we forget, shaping our memory according to how it is used

Michael Anderson

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Puzzle Unfinished Mess

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Scientists identify mechanism that helps us inhibit unwanted thoughts

cjb250 — Fri, 03 Nov 2017 09:13:20 +0000

We are sometimes confronted with reminders of unwanted thoughts — thoughts about unpleasant memories, images or worries. When this happens, the thought may be retrieved, making us think about it again even though we prefer not to. While being reminded in this way may not be a problem when our thoughts are positive, if the topic was unpleasant or traumatic, our thoughts may be very negative, worrying or ruminating about what happened, taking us back to the event.

“Our ability to control our thoughts is fundamental to our wellbeing,” explains Professor Michael Anderson from the Medical Research Council Cognition and Brain Sciences Unit, which recently transferred to the ̽��ֱ�� of Cambridge. “When this capacity breaks down, it causes some of the most debilitating symptoms of psychiatric diseases: intrusive memories, images, hallucinations, ruminations, and pathological and persistent worries. These are all key symptoms of mental illnesses such as PTSD, schizophrenia, depression, and anxiety.”

Professor Anderson likens our ability to intervene and stop ourselves retrieving particular memories and thoughts to stopping a physical action. “We wouldn’t be able to survive without controlling our actions,” he says. “We have lots of quick reflexes that are often useful, but we sometimes need to control these actions and stop them from happening. There must be a similar mechanism for helping us stop unwanted thoughts from occurring.”

A region at the front of the brain known as the prefrontal cortex is known to play a key role in controlling our actions and has more recently been shown to play a similarly important role in stopping our thoughts. ̽��ֱ��prefrontal cortex acts as a master regulator, controlling other brain regions – the motor cortex for actions and the hippocampus for memories.

In research published today in the journal Nature Communications, a team of scientists led by Dr Taylor Schmitz and Professor Anderson used a task known as the ‘Think/No-Think’ procedure to identify a significant new brain process that enables the prefrontal cortex to successfully inhibit our thoughts.

In the task, participants learn to associate a series of words with a paired, but otherwise unconnected, word, for example ordeal/roach and moss/north. In the next stage, participants are asked to recall the associated word if the cue is green or to suppress it if the cue is red; in other words, when shown ‘ordeal’ in red, they are asked to stare at the word but to stop themselves thinking about the associated thought ‘roach’.

Using a combination of functional magnetic resonance imaging (fMRI) and magnetic resonance spectroscopy, the researchers were able to observe what was happening within key regions of the brain as the participants tried to inhibit their thoughts. Spectroscopy enabled the researchers to measure brain chemistry, and not just brain activity, as is usually done in imaging studies.

Professor Anderson, Dr Schmitz and colleagues showed that the ability to inhibit unwanted thoughts relies on a neurotransmitter – a chemical within the brain that allows messages to pass between nerve cells – known as GABA. GABA is the main ‘inhibitory’ neurotransmitter in the brain, and its release by one nerve cell can suppress activity in other cells to which it is connected. Anderson and colleagues discovered that GABA concentrations within the hippocampus – a key area of the brain involved in memory – predict people’s ability to block the retrieval process and prevent thoughts and memories from returning.

“What’s exciting about this is that now we’re getting very specific,” he explains. “Before, we could only say ‘this part of the brain acts on that part’, but now we can say which neurotransmitters are likely important – and as a result, infer the role of inhibitory neurons – in enabling us to stop unwanted thoughts.”

“Where previous research has focused on the prefrontal cortex – the command centre – we’ve shown that this is an incomplete picture. Inhibiting unwanted thoughts is as much about the cells within the hippocampus – the ‘boots on the ground’ that receive commands from the prefrontal cortex. If an army’s foot-soldiers are poorly equipped, then its commanders’ orders cannot be implemented well.”

̽��ֱ��researchers found that even within his sample of healthy young adults, people with less hippocampal GABA (less effective ‘foot-soldiers’) were less able to suppress hippocampal activity by the prefrontal cortex—and as a result much worse at inhibiting unwanted thoughts.

̽��ֱ��discovery may answer one of the long-standing questions about schizophrenia. Research has shown that people affected by schizophrenia have ‘hyperactive’ hippocampi, which correlates with intrusive symptoms such as hallucinations. Post-mortem studies have revealed that the inhibitory neurons (which use GABA) in the hippocampi of these individuals are compromised, possibly making it harder for the prefrontal cortex to regulate activity in this structure. This suggests that the hippocampus is failing to inhibit errant thoughts and memories, which may be manifest as hallucinations.

According to Dr Schmitz: “ ̽��ֱ��environmental and genetic influences that give rise to hyperactivity in the hippocampus might underlie a range of disorders with intrusive thoughts as a common symptom.”

In fact, studies have shown that elevated activity in the hippocampus is seen in a broad range of conditions such as PTSD, anxiety and chronic depression, all of which include a pathological inability to control thoughts – such as excessive worrying or rumination.

While the study does not examine any immediate treatments, Professor Anderson believes it could offer a new approach to tackling intrusive thoughts in these disorders. “Most of the focus has been on improving functioning of the prefrontal cortex,” he says, “but our study suggests that if you could improve GABA activity within the hippocampus, this may help people to stop unwanted and intrusive thoughts.”

̽��ֱ��research was funded by the Medical Research Council.

Reference
Schmitz, TW et al. Hippocampal GABA enables inhibitory control over unwanted thoughts. Nature Communications; 3 Nov 2017; DOI: 10.1038/s41467-017-00956-z

Scientists have identified a key chemical within the ‘memory’ region of the brain that allows us to suppress unwanted thoughts, helping explain why people who suffer from disorders such as anxiety, post-traumatic stress disorder (PTSD), depression, and schizophrenia often experience persistent intrusive thoughts when these circuits go awry.

Our ability to control our thoughts is fundamental to our wellbeing. When this capacity breaks down, it causes some of the most debilitating symptoms of psychiatric diseases

Michael Anderson

Jacob Bøtter

Thinking RFIP

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Recalling memories may make us forget

cjb250 — Mon, 16 Mar 2015 16:00:00 +0000

̽��ֱ��research, published today in Nature Neuroscience, is the first to isolate the adaptive forgetting mechanism in the human brain. ̽��ֱ��brain imaging study shows that the mechanism itself is implemented by the suppression of unique patterns in the cortex that underlie competing memories. Via this mechanism, remembering dynamically alters which aspects of our past remain accessible.

In a study funded by the Medical Research Council (MRC), researchers monitored patterns of brain activity in the participants using magnetic resonance imaging (MRI) scans while the participants were asked to recall individual memories based on images they had been shown earlier.

̽��ֱ��team from the ̽��ֱ�� of Cambridge, the MRC Cognition and Brain Sciences Unit, Cambridge, and the ̽��ֱ�� of Birmingham, was able to track the brain activity induced by individual memories and show how this suppressed others by dividing the brain into tiny voxels (3D pixels). Based on the fine-grained activation patterns of these voxels, the researchers were able to witness the neural fate of individual memories as they were initially reactivated, and subsequently suppressed.

Over the course of four selective retrievals the participants in the study were cued to retrieve a target memory, which became more vivid with each trial. Competing memories were less well reactivated as each trial was carried out, and indeed were pushed below baseline expectations for memory, supporting the idea that an active suppression of memory was taking place.

Dr Michael Anderson from the MRC Cognition and Brain Sciences Unit and the Behavioural and Clinical Neurosciences Institute at the ̽��ֱ�� of Cambridge said: “People are used to thinking of forgetting as something passive. Our research reveals that people are more engaged than they realise in shaping what they remember of their lives. ̽��ֱ��idea that the very act of remembering can cause forgetting is surprising, and could tell us more about selective memory and even self-deception.”

Dr Maria Wimber from the ̽��ֱ�� of Birmingham added: “Forgetting is often viewed as a negative thing, but of course, it can be incredibly useful when trying to overcome a negative memory from our past. So there are opportunities for this to be applied in areas to really help people.”

̽��ֱ��team note that their findings may have implications for the judicial process, for example, in eyewitness testimonies. When a witness is asked to recall specific information about an event and is quizzed time and time again, it could well be to the detriment of associated memories, giving the impression that their memory is sketchy.

Studying the neural basis of forgetting has proven challenging in the past because the ’engram’ – the unique neural fingerprint that an experience leaves in our memory – has been difficult to pinpoint in brain activity. By capitalising on the relationship between perception and memory, the study detected neural activity caused by the activation of individual memories, giving a unique window into the invisible neurocognitive processes triggered when a reminder recapitulates several competing memories.

Adapted from a press release by the Medical Research Council.

Reference
Wimber, M et al. Retrieval induces adaptive forgetting of competing memories via cortical pattern suppression. Nature Neuroscience; 16 March 2015

Intentionally recalling memories may lead us to forget other competing experiences that interfere with retrieval, according to a study published today. In other words, the very act of remembering may be one of the major reasons why we forget.

̽��ֱ��idea that the very act of remembering can cause forgetting is surprising, and could tell us more about selective memory and even self-deception

Michael Anderson

Sara

Forgetting

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Out of mind, out of sight: suppressing unwanted memories reduces their unconscious influence on behaviour

jfp40 — Tue, 18 Mar 2014 12:09:10 +0000

̽��ֱ��study, part-funded by the Medical Research Council (MRC) and published online in PNAS, challenges the idea that suppressed memories remain fully preserved in the brain’s unconscious, allowing them to be inadvertently expressed in someone’s behaviour. ̽��ֱ��results of the study suggest instead that the act of suppressing intrusive memories helps to disrupt traces of the memories in the parts of the brain responsible for sensory processing.

̽��ֱ��team at the MRC Cognition and Brain Sciences Unit and the ̽��ֱ�� of Cambridge’s Behavioural and Clinical Neuroscience Institute (BCNI) have examined how suppression affects a memory’s unconscious influences in an experiment that focused on suppression of visual memories, as intrusive unwanted memories are often visual in nature.

After a trauma, most people report intrusive memories or images, and people will often try to push these intrusions from their mind, as a way to cope. Importantly, the frequency of intrusive memories decreases over time for most people. It is critical to understand how the healthy brain reduces these intrusions and prevents unwanted images from entering consciousness, so that researchers can better understand how these mechanisms may go awry in conditions such as post-traumatic stress disorder.

Participants were asked to learn a set of word-picture pairs so that, when presented with the word as a reminder, an image of the object would spring to mind. After learning these pairs, brain activity was recorded using functional magnetic resonance imaging (fMRI) while participants either thought of the object image when given its reminder word, or instead tried to stop the memory of the picture from entering their mind.

̽��ֱ��researchers studied whether suppressing visual memories had altered people’s ability to see the content of those memories when they re-encountered it again in their visual worlds. Without asking participants to consciously remember, they simply asked people to identify very briefly displayed objects that were made difficult to see by visual distortion. In general, under these conditions, people are better at identifying objects they have seen recently, even if they do not remember seeing the object before—an unconscious influence of memory. Strikingly, they found that suppressing visual memories made it harder for people to later see the suppressed object compared to other recently seen objects.

Brain imaging showed that people’s difficulty seeing the suppressed object arose because suppressing the memory from conscious awareness in the earlier memory suppression phase had inhibited activity in visual areas of the brain, disrupting visual memories that usually help people to see better. In essence, suppressing something from the mind’s eye had made it harder to see in the world, because visual memories and seeing rely on the same brain areas: out of mind, out of sight.

Over the last decade, research has shown that suppressing unwanted memories reduces people’s ability to consciously remember the experiences. ̽��ֱ��researchers’ studies on memory suppression have been inspired, in part, by trying to understand how people adapt memory after psychological trauma. Although this may work as a coping mechanism to help people adapt to the trauma, there is the possibility that if the memory traces were able to exert an influence on unconscious behaviour, they could potentially exacerbate mental health problems. ̽��ֱ��idea that suppression leaves unconscious memories that undermine mental health has been influential for over a century, beginning with Sigmund Freud.

These findings challenge the assumption that, even when supressed, a memory remains fully intact, which can then be expressed unconsciously. Moreover, this discovery pinpoints the neurobiological mechanisms underlying how this suppression process happens, and could inform further research on uncontrolled ‘intrusive memories’, a classic characteristic of post-traumatic stress disorder.

Dr Michael Anderson, at the MRC Cognition and Brain Sciences Unit said: “While there has been a lot of research looking at how suppression affects conscious memory, few studies have examined the influence this process might have on unconscious expressions of memory in behaviour and thought. Surprisingly, the effects of suppression are not limited to conscious memory. Indeed, it is now clear, that the influence of suppression extends beyond areas of the brain associated with conscious memory, affecting perceptual traces that can influence us unconsciously. This may contribute to making unwanted visual memories less intrusive over time, and perhaps less vivid and detailed.”

Dr Pierre Gagnepain, lead author at INSERM in France said: “Our memories can be slippery and hard to pin down. Out of hand and uncontrolled, their remembrance can haunt us and cause psychological troubles, as we see in PTSD. We were interested whether the brain can genuinely suppress memories in healthy participants, even at the most unconscious level, and how it might achieve this. ̽��ֱ��answer is that it can, though not all people were equally good at this. ̽��ֱ��better understanding of the neural mechanisms underlying this process arising from this study may help to better explain differences in how well people adapt to intrusive memories after a trauma”

New research shows that, contrary to what was previously assumed, suppressing unwanted memories reduces their influence on behaviour, and sheds light on how this process happens in the brain.

It is now clear that the influence of suppression extends beyond areas of the brain associated with conscious memory. This may contribute to making unwanted visual memories less intrusive over time, and perhaps less vivid and detailed.

Dr Michael Anderson

QThomas Bower

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