Brain Pathway To Control Sleep
Channel: Health Spot
Date: 17/11/2022

Sleep has a profound influence on how we feel and function. But simply clocking a lot of Zs is not enough; the type of sleep matters too. Researchers have long known that a night's rest includes multiple types of sleep, each of which restores the mind and body in a specific way. But how we slip from one type to the next has remained unclear--until now. In a new study, researchers identified a brain circuit that controls sleep stage transitions, potentially revealing a path to improve sleep aids.
Sleep can be divided into two basic types: rapid eye movement, or REM, and non-rapid eye movement, or NREM. Brain activity during REM sleep is fast and irregular, much like during wakefulness. In contrast, NREM sleep is deep, with slow and rhythmic activity. This slow, steady rhythm is possible because of the coordination of two brain regions: the cortex and thalamus.   
Here, the research team studied one of the ways that the cortex and thalamus communicate - through a specific pair of proteins: the type 1 metabotropic glutamate receptor and the PLCβ4 enzyme. The metabotropic glutamate receptor in the thalamus receives the cortical input. To figure out how this particular pathway influences sleep, researchers used mutant mice lacking the enzyme. 
When the team evaluated the sleep patterns of the animals, they found that the mutant mice spent more time in NREM sleep and had fewer REM episodes. Because NREM sleep always comes before REM, these results show that loss of this signaling disrupted the transition from NREM to REM and distorted how much of each sleep type the mice got. The mutants also had abnormally strong rhythmic activity in the thalamus, indicating that sleep quality may have been harmed as well. 
Taken together, the results suggest that this signaling pathway enables the cortex to control the transition from NREM to REM sleep by regulating activity in the thalamus. Targeting this pathway could help mitigate the negative effects of too little REM sleep, such as memory problems and weight gain, and allow more people to get a full, healthy night’s rest.