A note to the forgetful: be thankful you don鈥檛 remember everything. It means your brain is working properly.
According to a new study, the brain only chooses to remember memories it thinks are most relevant, and actively suppresses those that are similar but less used, helping to lessen the cognitive load and prevent confusion.
Brice Kuhl at Stanford University in California, US, and colleagues used functional magnetic resonance imaging (fMRI) to measure the brain activity of 20 healthy adults while they performed a simple memory test. Participants were given three words pairs to memorise, including two pairs that were closely associated, as follows:
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- ATTIC dust
- ATTIC junk
- MOVIE reel
After studying 鈥淎TTIC dust鈥� a second time, subjects were asked to recall all three pairs using the first words as cues. On average, people were 15% worse at recalling 鈥淎TTIC junk鈥� than they were at recalling the unrelated pair, 鈥淢OVIE reel鈥�.
Initial suppression
Comparing these findings to the fMRI data taken during the test, the team found participants鈥� brains were highly active in a region known for handling competing memories, and also in an area believed to induce memory suppression.
The researchers believe that the first region identified 鈥淎TTIC dust鈥� and 鈥淎TTIC junk鈥� as conflicting memories. The second region then suppressed 鈥淎TTIC junk鈥� because it had only been seen once.
As the test was readministered a second and third time, suppression activity lessened, indicating the memory adjustment had been made.
Prioritising memories
鈥淲henever you鈥檙e engaging in remembering, the brain adapts. It鈥檚 constantly re-weighting memories,鈥� says Kuhl. 鈥淚n this simple test, we see it reverse memory to weaken competing memories. This is something that probably happens a lot in the real world.鈥�
A good example is the confusion that arises when we change passwords on our computers or email accounts. We often mix up old and new passwords at first, but through repetition we develop a strong memory of the new password and forget the old one.
鈥淭he process of forgetting serves a good functional purpose,鈥� says Michael Anderson of the University of Oregon, US, who was not involved in the study. 鈥淲hat these guys have done is clearly establish the neurobiological basis for this process.鈥�
Journal reference: Nature Neuroscience (DOI:10.1038/nn1918)
