22 Mar

Clear Out Your Attic………Often

For the Brain, a Race To Recall the Details

It is always a challenge to remember a new computer password after an old one has expired, or to memorize a new phone number.

That is because the brain is competing to recall old memories and new ones that are associated with the same thing, researchers from Yale and Stanford report (**see abstract below) in Proceedings of the National Academy of Sciences.

Brice Kuhl, a psychologist at Yale, and his colleagues found that when the brain is cluttered with similar events, the difficulty in recalling just one of them is visible through the brain-scanning technology known as functional magnetic resonance imaging.

The researchers provided subjects with words that had both face associations and scene associations. When they ran a scan and asked the subjects to recall the association they had most recently seen, blood flowed in parts of the brain that are used to recall faces and scenes.

Most people regularly encounter this competition.

“I park in a garage every day at work, and I park in a different space every day, depending on availability,” Dr. Kuhl said. “And I very often walk to where I parked the day before. It’s not that I totally forgot where I parked, it’s just that I still remember yesterday’s spot.”

* Updated: to “no one”.



Remembering an event from the past is often complicated by the fact that our memories are cluttered with similar events. Though competition is a fundamental part of remembering, there is little evidence of how mnemonic competition is neurally represented. Here, we assessed whether competition between visual memories is captured in the relative degree to which target vs. competing memories are reactivated within the ventral occipitotemporal cortex (VOTC). To assess reactivation, we used multivoxel pattern analysis of fMRI data, quantifying the degree to which retrieval events elicited patterns of neural activity that matched those elicited during encoding. Consistent with recent evidence, we found that retrieval of visual memories was associated with robust VOTC reactivation and that the degree of reactivation scaled with behavioral expressions of target memory retrieval. Critically, competitive remembering was associated with more ambiguous patterns of VOTC reactivation, putatively reflecting simultaneous reactivation of target and competing memories. Indeed, the more weakly that target memories were reactivated, the more likely that competing memories were later remembered. Moreover, when VOTC reactivation indicated that conflict between target and competing memories was high, frontoparietal mechanisms were markedly engaged, revealing specific neural mechanisms that tracked competing mnemonic evidence. Together, these findings provide unique evidence that neural reactivation captures competition between individual memories, providing insight into how well target memories are retrieved in the present and how likely competing memories will be remembered in the future.

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