London: Our brain remains constantly at work, even if the body is at rest. According to a study, the memories that are formed in one part of the brain are replayed and transferred to another area of the brain for long-term storage, even while our bodies take rest.
"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," said lead researcher, Freyja Olafsdottir, research associate at University College London, in Britain.
Replay of previous experiences during rest is important for memory consolidation, a process whereby the brain stabilises and preserves memories for quick recall in the future.
The researchers, in the paper published in Nature Neuroscience, investigated the role of sleep in memory consolidation by simultaneously studying two areas of the brain as the rats rested after activity.
The findings showed that the rats re-ran memories in their minds as they rested and 10-20 times faster.
The same replay happened almost simultaneously, with a 10-millisecond delay, in grid cells located in a different part of the brain, suggesting that the rats' memories transferred from one part of the brain to another.
During rest, the team studied the responses of place cells in the hippocampus in brain, where memories are formed, and grid cells in the entorhinal cortex, where the memories were found to transfer to.
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 safekeeping and easy access.
"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," said one of the researchers Caswell Barry.
Understanding the physiological mechanism of this is essential for tackling amnesiac conditions such as Alzheimer's disease, where memory consolidation is affected, the researchers said.
"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," Olafsdottir said.
Six rats were made to run for 30 minutes on a six metre long track before resting for 90 minutes. Their brains were then studied to investigate memory transfer to other areas of the brain.