Deep sleep could 'boost memory'

New research has shown how sleep impacts memory. It's well established that getting enough rest at night can help you to remember what happened during the day, and now a team from Japan's RIKEN Brain Science Institute has pinpointed the exact part of the brain involved in this.

This finding could help to better treat neurological disorders like Alzheimer's disease and improve dementia care across the world.

Published in Science magazine, the study highlighted a key neural connection that can either prevent or enhance the retention of memories during periods of deep sleep.

Professor Masanori Murayama from the Behavioral Neurophysiology department at the RIKEN Brain Science Institute led the research, which built on a previous study he had conducted into tactile perception.

During this earlier research, the team found that being able to notice different textures relies on communication between higher-level motor-related brain regions and lower-level touch-related sensory areas.

They concluded that the same "top-down" pathway could also consolidate memories of textures.

"There is a long-standing hypothesis that top-down input is crucial for memory consolidation and that, during sleep, neurons in sensory regions activated during the initial experience can "reactivate" by unknown pathways. We found such reactivation of the top-down pathway is critical for mice to encode memories of their tactile experiences," Professor Murayama explained.

In his latest study, he created a task that could assess memory retention that relied on the natural inclination of mice to spend more time investigating new items in their environment.

Firstly, mice were allowed to explore objects in two rooms with smooth floors, then the team changed one of the floors to a textured one and the mice were again able to explore their environment.

When the mice got a normal night's sleep, the study found that they spent more time exploring the room with the textured floor, suggesting that they were able to remember the smooth room, as they were less interested when revisiting this space.

"Our findings on sleep deprivation are particularly interesting from a clinical perspective," says Professor Murayama.

He added that patients who suffer from sleep disorders often have impaired memory functions and the findings suggest a potential route to treatment using transcortical magnetic or direct-current stimulation to top down cortical pathways to reactivate sleep-deprived neurons during non-REM sleep.

Professor Murayama said the next step was to investigate this in sleep disorders to see whether the findings would change.

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