For the first time ever, scientists may have solidified a link between memory formation and REM sleep. We know that a bad night’s sleep can leave our heads in a fog and may even cause irritability, but it turns out a bad night’s sleep could also rob us of our memories. 
Researchers from Canada and Switzerland report that without the deep sleep of a REM cycle, the brain fails to organize and coordinate spatial and emotional memory. The researchers also suggested this may account for some part of the memory problems Alzheimer’s patients experience as a result of poor sleep patterns.
To prove the importance of the REM cycle of sleep on memory, researchers used mice with a genetically modified variation allowing researchers to “turn-off” a part of the brain. With light pulses, researchers were able to turn off brain cells associated with REM sleep in the hippocampus, the part of the brain that controls memory.
When those brain cells were turned off during the REM portion of sleep, the mice failed to perform tasks they had learned the previous day. Turning off those brain cells during any other part of their sleep cycle had no effect on their memory or ability to perform recently-learned tasks.
REM sleep makes up one of five stages of a normal sleep cycle and 25% of sleep every night. A good night’s sleep includes 4 to 5 REM cycles for an adult.
This study demonstrated conclusively that memory coordination, the time when the brain organizes spatial and emotion memory, occurs only during the REM stage of sleep. While it’s not known yet whether poor sleep contributes to Alzheimer’s disease itself, your ability to function everyday relies on your getting enough sleep.
Here is what the study abstract has to say:
“Rapid eye movement sleep (REMS) has been linked with spatial and emotional memory consolidation. However, establishing direct causality between neural activity during REMS and memory consolidation has proven difficult because of the transient nature of REMS and significant caveats associated with REMS deprivation techniques.
In mice, we optogenetically silenced medial septum γ-aminobutyric acid–releasing (MSGABA) neurons, allowing for temporally precise attenuation of the memory-associated theta rhythm during REMS without disturbing sleeping behavior.
REMS-specific optogenetic silencing of MSGABA neurons selectively during a REMS critical window after learning erased subsequent novel object place recognition and impaired fear-conditioned contextual memory. Silencing MSGABA neurons for similar durations outside REMS episodes had no effect on memory.
These results demonstrate that MSGABA neuronal activity specifically during REMS is required for normal memory consolidation.”
How to Get a Good Night’s Sleep
To get a good night’s sleep, the Sleep Foundation recommends setting a regular bedtime routine that gives you a chance to wind down, even on weekends. An adult requires 7 to 8 hours of sleep every night. To help regulate your body’s natural wake-sleep rhythms, you can use bright light. Expose yourself to it in the morning and avoid it at night.
This includes mobile devices, computer screens, and TV. While a quick peak at a mobile device may not seem like a problem, studies have shown mobile use within one hour before going to bed disrupts normal sleep patterns in both adults and children.  
The Sleep Foundation also recommends these approaches to ease yourself into a restful night’s sleep. Eat lighter evening meals. Avoid drinking water or other beverages that might wake you to use the washroom. And sleep on supportive and comfortable mattress, pillows and sheets in a temperature between 60 to 67 degrees.
 Science News
 Science Direct