Memory lapses ‘key part of learning’

It is a common, yet embarrassing, scenario but British scientists have offered an insight into why we forget people’s names only for them to return hours later.

Scientists have observed that, in all animals, memories that can be recalled several hours after learning them may become inaccessible for brief periods after their formation.

It is believed such lapses occur because they are a necessary part of the brain’s process to consolidate memories.

University of Sussex neuroscientists found that causing a disturbance during these memory lapses disrupts the process and appears to prevent the memories being formed.

One of the experts involved in the study, Ildiko Kemenes, said: “Scientists have long wondered why the brain shows these memory lapses.

“Here we showed that lapses in memory coincide with periods when consolidation of memory is susceptible to disturbances from outside the memory network.

“Changes in the molecular pathways underlying consolidation are responsible for these periods of vulnerability.”

Kemenes and colleagues introduced snails to an unfamiliar substance during feeding so the animals would learn to recognise it as food.

When they were fed later, the snails responded to the stimulus, with memory lapses after 30 minutes and two hours, before the memory became consolidated at about four hours.

But if the snail received another different stimulus during the memory-lapse periods, the memory consolidation became disrupted, it was discovered.

“Memory formation is an energy-consuming process,” said Kemenes. “The brain would need to decide if it was worth expending energy for the consolidation of that particular memory.

“The brain has a restricted capacity to learn things and preventing some memory formation would be a way to avoid overload.”

The next stage of the study will investigate what happens to the brain during the memory disruption.

Co-investigator Paul Benjamin said: “We hadn’t realised quite how complicated the process would be.

“It could be that, rather than just disrupting the original stimulus, the brain is creating a new memory from the second stimulus.”

* Susceptibility of memory consolidation during lapse in recall, by Vincenzo Marra, Michael O’Shea, Paul R Benjamin, and Ildiko Kemenes, is published in Nature Communications.

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