Study looks at how brain ‘resets’ itself while sleeping, allows lifelong learning

New Delhi: While sleep is known to help with forming and storing memories during the day, a new study has found answers to how this continues to happen over one’s lifetime without running out of neurons or brain cells.

Researchers found that at certain times during deep sleep, certain parts of the hippocampus — one of the brain regions involved in learning new things and forming memories — go silent, allowing those neurons to ‘reset’.

“This mechanism could allow the brain to reuse the same resources, the same neurons, for new learning the next day,” said Azahara Oliva, an assistant professor of neurobiology and behaviour at Cornell University, US, and corresponding author of the study published in the journal Science.

While we sleep, the brain cells go over everything we learn or experience during the day by repeating the patterns that were activated the first time, thereby helping with how memories are stored.

The process is called ‘memory consolidation’, following which the memories are then stored in a large area in the brain called the cortex. Both the hippocampus and the cortex play a role in memory, with the hippocampus transferring temporary or ‘short-term’ information to the cortex to form permanent or ‘long-term’ memories.

The researchers said that the hippocampus is divided into three regions, two of which are well-known to help form memories related to time and space. The third, they said, is involved in silencing and resetting parts of the hippocampus during sleep, which this study found.

“We realised there are other hippocampal states that happen during sleep where everything is silenced. The (two) regions that had been very active were suddenly quiet. It’s a reset of memory, and this state is generated by the (third) region,” Oliva said.

For the study, the researchers implanted electrodes into the hippocampi of the brains of mice, which are commonly studied as they are known to bear genetic material similar to humans. This allowed the team to observe the brain’s activity during learning and sleep, they said.

The study’s results help explain why all animals require sleep, not only to fix memories but also to reset the brain and keep it working during waking hours, the researchers said.

They believe that by tinkering with the processes at play during memory consolidation, they now have the tools to boost memory.

The tools could be applied when memory function falters, such as in Alzheimer’s disease, in which memory and decision-making are impaired, thereby interfering with one’s daily activities, the authors said.

They also said that the evidence could be used to explore means for erasing negative or traumatic memories, which could then help treat conditions such as post-traumatic stress disorder.