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Our brain has an alert system to shut down unwanted memories

A new study published by the Society for Neuroscience describes an “alarm system” in the brain that helps suppress unwanted thoughts. According to the experts, this brain region proactively detects unwanted memories and responds by alerting other areas of the brain to inhibit them. 

“Preventing unwanted memories from coming to mind is an adaptive ability of humans. This ability relies on inhibitory control processes in the prefrontal cortex to modulate hippocampal retrieval processes. How and when reminders to unwelcome memories come to trigger prefrontal control mechanisms remains unknown,” wrote study lead author Maité Crespo García and colleagues.

As study participants executed a memory task, the experts measured brain activity with both EEG and fMRI. The volunteers were asked to memorize sets of words, such as gate and train. They were instructed to either recall the pair of words by association (see a gate, think about a train), or to focus only on the cue word (see a gate, only think about the gate). 

When the participants were proactively suppressing a memory, the experts found  that activity increased in the anterior cingulate cortex (ACC), a brain region  cognitive control. This area of the brain connects to both the emotional limbic system and the cognitive prefrontal cortex. The ACC plays an important role in “affect-regulation,” the ability to control uncomfortable emotions.

Elevated activity in the ACC was detected within the first 500 milliseconds of the proactive memory suppression task, according to the study authors. The ACC was found to relay information to the dorsolateral prefrontal cortex (DLPFC), which then inhibited activity in the hippocampus – a region that regulates memory recall. 

When memory suppression was successful, activity levels in the ACC and DLPFC remained low throughout the remainder of the trial. On the other hand, if the memory was not quickly suppressed, the anterior cingulate cortex ramped up its activity to alert the DLPFC to stop the intrusion.

“Here we acquired neuroimaging data with both high spatial and temporal resolution as participants suppressed specific memories,” explained the researchers.

“We found that the anterior cingulate cortex detects the need for memory control, responding both proactively to early warning signals about unwelcome content and reactively to intrusive thoughts themselves.”

“When unwanted traces emerge in awareness, anterior cingulate communicates with prefrontal cortex and triggers top-down inhibitory control over the hippocampus through specific neural oscillatory networks.”

The study is published in the journal JNeurosci.

By Chrissy Sexton, Staff Writer

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