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New study of brain imaging suggests that in order to forget, we must first do a little remembering

Hippocampal neuron in culture. Dendrites are green, dendritic spines are red and DNA in cells nucleus is blue.
Hippocampal neuron in culture. Dendrites are green, dendritic spines are red and DNA in cells nucleus is blue.
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How does our brain decide what information it stores and what we forget? And are humans at all able to influence what things we remember and what we forget?

Conventional wisdom might suggest that certain memories are forgotten over time and as less attention is paid to them. But a new study published last month in The Journal of Neuroscience explores whether and how humans can harness the power of the brain to voluntarily forget something. And contrary to conventional wisdom, it turns out that if you want to make a memory vanish, you might have to think about it a bit first.

For the experiment, researchers placed subjects in an MRI machine and then showed them a series of about 200 images. They were then told to remember or forget each image, and the researchers studied activity in areas of the brain that light up when focusing on simple images. After a short rest, the subjects were shown another series of images -- some they’d seen in the previous series and some they hadn’t -- and were asked to rate how certain they were they’d seen or not seen one. Overall, participants remembered 50-60% of images they were told to remember and successfully forgot about 40% of the images they were told to forget. And when the research team looked at the brain imaging, they discovered that very high or very low levels of brain activity were usually linked to a failed attempt to forget one of the images. It didn’t help a person to forget something if he or she focused really hard on forgetting it or tried to mentally ignore it, but in that sweet spot between the two was where subjects were most successful in forgetting unwanted memories.

What can we learn from the findings of this study about humans’ ability to voluntarily forget certain memories? How could this power be harnessed to help certain groups of people? Are there potential unintended consequences?


Tracy Wang, lead researcher on the study “More is less: increased processing of unwanted memories facilitates forgetting” (Journal of Neuroscience, March 2019) and a postdoctoral psychology fellow at The University of Texas at Austin; she tweets @TweetTwang