Memories are made by the brain filing them in a ‘library’ whilst we rest, new research reveals.

And the finding could help treat conditions such as Alzheimer’s.

Memories are made by one part of the brain before being replayed at 20 times the speed and stored in another part of the brain according to the research.

The team at University College London investigated the role of sleep in memory consolidation by simultaneously studying two areas of the brain as rats rested following activity.

The rodents were placed on a six-metre track where they ran for 30 minutes.

They were then allowed to rest for 90 minutes, during which time their brain activity was monitored.

The scientists watched the responses of ‘place cells’ in the hippocampus, where memories are formed, and ‘grid cells’ in the entorhinal cortex, to where the memories are transferred.

Responses from the place cells showed that the rats ‘re-ran’ the track in their mind, between 10 and 20 times faster that they experience in real time.

But interestingly, the rats’ grid cells repeated the same replay almost instantaneously, albeit with a 10 millisecond delay – suggesting that the brain transferred the memories to another part of the brain.

Lead researcher, Dr Freyja Ólafsdóttir (doub corr), said: “We want to understand how a healthy brain stores and accesses memories as this will give us a window into how conditions such as Alzheimer’s disease disrupt the process.

“We know people with Alzheimer’s have difficulty recalling the recent past but can often readily remember childhood memories, which seem more resilient.

“The parts of the brain we studied are some of the first regions affected in Alzheimer’s and now we know they are also involved in memory consolidation.”

The study was published in Nature Neuroscience.

Supervisor, Dr Caswell Barry, said: “This is the first time we’ve seen coordinated replay between two areas of the brain known to be important for memory, suggesting a filing of memories from one area to another.

“The hippocampus constantly absorbs information but it seems it can’t store everything so replays the important memories for long term storage and transfers them to the entorhinal cortex, and possibly on to other areas of the brain, for safe-keeping and easy access.”

Now researchers plan to investigate memory transfer to other areas of the brain in rats with Alzheimer’s disease to better understand the memory consolidation mechanism and the link between quality of sleep and amnesiac conditions.

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