Choosing to forget something uses more brain power than trying to remember it, according to a study that could lead to treatments to help people rid themselves of unwanted memories.
The findings, published in the Journal of Neuroscience, suggest that in order to forget an unwanted experience, more attention should be focused on it.
The study extends prior research on intentional forgetting, which focused on reducing attention to the unwanted information through redirecting attention away from unwanted experiences or suppressing the memory's retrieval.
"We may want to discard memories that trigger maladaptive responses, such as traumatic memories, so that we can respond to new experiences in more adaptive ways," said Jarrod Lewis-Peacock, an assistant professor at The University of Texas at Austin in the US.
"Once we can figure out how memories are weakened and devise ways to control this, we can design treatment to help people rid themselves of unwanted memories," Lewis-Peacock.
Memories are are dynamic constructions of the brain that regularly get updated, modified and reorganised through experience.
The brain is constantly remembering and forgetting information -- and much of this happens automatically during sleep.
Prior studies focused on locating "hotspots" of activity in the brain's control structures, such as the prefrontal cortex, and long-term memory structures, such as the hippocampus.
The latest study focuses, instead, on the sensory and perceptual areas of the brain, specifically the ventral temporal cortex, and the patterns of activity there that correspond to memory representations of complex visual stimuli.
"We are looking not at the source of attention in the brain, but the sight of it," said Lewis-Peacock.
Using neuroimaging to track patterns of brain activity, the researchers showed a group of healthy adults images of scenes and faces, instructing them to either remember or forget each image.
Their findings not only confirmed that humans have the ability to control what they forget, but that successful intentional forgetting required "moderate levels" of brain activity in these sensory and perceptual areas -- more activity than what was required to remember.
"A moderate level of brain activity is critical to this forgetting mechanism. Too strong, and it will strengthen the memory; too weak, and you won't modify it," said Tracy Wang, lead author of the study and a psychology postdoctoral fellow at UT Austin.
"Importantly, it is the intention to forget that increases the activation of the memory, and when this activation hits the 'moderate level' sweet spot, that is when it leads to later forgetting of that experience," Wang said.
The researchers also found that participants were more likely to forget scenes than faces, which can carry much more emotional information, the researchers said.
"This will make way for future studies on how we process, and hopefully get rid of, those really strong, sticky emotional memories, which can have a powerful impact on our health and well-being," Lewis-Peacock said.
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