Researchers at the Douglas Mental Health University Institute (McGill University) and the University of Bern confirm that rapid eye movement (REM) sleep is crucial for the formation of normal spatial memory. The study published online on May 13 in the journal Science suggests that disruptions of REM sleep can lead to memory problems as seen in patients with Alzheimer’s disease and other neurodegenerative diseases.
The research team utilised optogenetics to control neurons that regulate the hippocampal activity, a part of the brain known as its GPS system and is important for memory formation when a person is awake. Optogenetics is a new technology that entails using light to target neurons and control its activity.
During their experiment, the researchers trained mice to spot a new object in a setting where objects with similar shape and volume are placed together. Their use of learning and recall enabled the rodents to spend more time exploring the new object than the old, familiar ones.
Using light, the researchers switched off the animals’ neurons associated with memory when the mice were in their REM sleep. The team observed that the mice with the switched-off neurons were not able to recall the novel object, suggesting that their spatial memory was completely erased or impaired.
“Silencing the same neurons for similar durations outside REM episodes had no effect on memory,” says lead author Richard Boyce. “This indicates that neuronal activity specifically during REM sleep is required for normal memory consolidation.”
The new study’s findings add to countless research that showed poor sleep is related to the onset of several neurodegenerative disorders characterised by memory problems such as Alzheimer’s and Parkinson’s disease.