From Dr. Matt Walker's book [[Why We Sleep]] - he presents the functions of REM and NREM sleep on the brain in this way. > [!tldr] > - **NREM** - clears way for new connections to be formed > - **REM** - uses some of that cleared space # NREM **Non-rapid Eye Movement** sleep is associated more predominantly with the first half of the [[Sleep Stages Cycle]]. Its role is essentially to determine what neuronal connections it can prune. What's not relevant. What's duplicative. > [!tldr] NREM sleep makes space for new connections in the brain. NREM is key for memory. You can think of it as shifting things out of your mind's RAM (hippocampus) into long-term storage (cortex). This both builds your retention of learned facts and creates space for new ones. What is stored in long-term memory during sleep is somehow guided toward what we believe is important. See the [[Sleep Recall Steering Experiments]] NREM is broken up into 3 substages - stages 1, 2, and 3. Where 1 is "light sleep", 3 is "deep sleep", and 2 is the transitional period between them. Sleepwalking happens during NREM sleep, which is surprising. # REM **Rapid Eye Movement** sleep is associated more predominantly with the second half of the [[Sleep Stages Cycle]]. Its role is essentially to formulate new and strengthen connections within the brain based on new experience. > [!tldr] REM builds new connections by assimilating recent experience. Alcohol inhibits REM sleep. Drinking causes your REM sleep to drop. This has been shown to ruin sleeps ability to cement memory. [[Drinking Disrupts the Benefits of Sleep]]. REM is also associated with dreaming. See [[The Function of Dreams]]. **** # More ## Source - [[Why We Sleep]]