My comment about the neuronal recovery during REM sleep comes from a published medical article. I follow a number of publications that report on the current research. Sometimes, I may mistake the details but not the principle. A recent report mentioned that the brain shuts down some brain cells while the others are active during REM sleep. This alternating of shut down cells vs active (REM) cells is thought to be when the cells recover. The shut down cells are in addition to the motor cells that are shut down and cause paralysis.

I follow a sleep disorders newsletter due to my own struggles with Central Sleep Apnea and what CSA did to my father's life.

My brain may mix the details so feel free to correct the details.