This is how the brain blocks unpleasant memories

Preventing unwanted memories from coming to mind is an adaptive ability of humans, which relies on inhibitory control processes in the prefrontal cortex responsible for modulating recovery processes in the hippocampus. This “unconscious” ability allows the individual to preserve himself. But scientists do not know how or when unwanted memory memories trigger these control mechanisms. A team of researchers was able to unravel this mystery using neuroimaging data, collected while volunteers were being asked to erase specific memories from their memory. The results of this study have just been published in Journal of Neuroscience.

An alarm signal in case of negative thoughts

The anterior cingulate cortex (ACC), located in the front of the skull and the surrounding part of the corpus callosum, is involved in a variety of autonomous functions, such as regulating blood pressure and heart rate, and cognitive skills. , as the anticipation of the reward. , decision making, empathy and emotion. Many studies have also shown the involvement of dorsal CCA (CCAd) in the subjective perception of physical pain. It is therefore not surprising that this brain region comes into play when it comes to soothing mental pain.

To better understand the mechanisms underlying the suppression of unpleasant memories, the researchers examined the brain activity of 24 participants using an electroencephalogram and a functional brain MRI while performing a memory task. It was precisely a matter of memorizing 64 pairs of unrelated words (for example, “door” and “train”), displayed side by side for 5 seconds; then, starting with a word, participants were invited to remember the word associated with it (see “door”, so think “train”) or, conversely, to curb this thought and focus only on the word represented. (see “door”, and think only of the door).

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Note that this experiment is based on the “think / not think” paradigm, developed in 2001 by psychologists Michael Anderson and Collin Green, to study the effect of the intention not to remember on memory.

During the exercise, while participants struggled not to remember one of the terms that formed a couple of words, the team observed a marked increase in CCAd activity in the first 500 milliseconds of the task. This part of the cortex then “relayed” the need for control to the dorsolateral prefrontal cortex (dlPFC), which plays an important role in the planning process and executive functions, which in turn, through neural networks. specific, inhibited hippocampal activity. a region of the brain that is known to be essential for memory.

An illustration of how the anterior cingulate cortex proactively and reactively indicates the need to suppress negative thoughts, such as associating a toy with a recently dead dog. Credits: M. García et al., JNeurosci (2022)

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An inhibition process essential to our well-being

The researchers noted that activity levels in CCAd and dlPFC remained relatively low throughout the duration of the trial, suggesting that the recovery process was stopped well in advance because no further suppression was needed. ” Lpreventing recovery reduces the general demands of neuronal control “If the memory was not cleared in time, the CCAd instructed the dlPFC to stop this intrusion by activating an alarm signal manifested by an increase in its activity.

We found a clear role of CCA by detecting the need to control memory and by regulating prefrontal inhibition. It is important to note that we have identified different contributions fromin CCA early (350-400 ms) and late (500-700 ms), suggesting both proactive control before recovery and reactive control in response to intrusions summarize the researchers. Therefore, this study demonstrated that CCAd detects the need to control memories and responds both proactively to the first signals of unwanted memories and reactively to intrusive thoughts that evade proactive suppression mechanisms.

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That is, in fact, memory inhibition is the basis of an effective memory system. In fact, inhibiting the recollection of irrelevant information is essential to remembering important things quickly and efficiently. But this process is also responsible for our well-being, a failure at this level can lead to negative thoughts. ” Our ability to control our thoughts is critical to our well-being. When this skill sinks, it causes certain […] Key Symptoms of Mental Illness such as Post Traumatic Stress Disorder, Schizophrenia, Depression and Anxiety “, explained Professor Michael Anderson in 2017, who participated in this new study.

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