Hi, a few years ago I'v seen and heard presentation of prof Kukwa Andrzej - ENT from Poland, Warsaw - about cranial nervs action during sleep. it was a symposium for snorring and OSAS. He reported and showed in his study - electrical potentials of several cranial nervs including vagus - X nerv - you can proove electr. potentials of muscles nerved by cranial nervs. There is phisiological vocal fold activity during a sleep - abduction during brath take, and adduction during exhaust. As well as phisiological activity of the nervs V,VII, IX, XII that helps us breath well during sleep.

Patophysiology of this activity can provide to snoring and sleep apneas, besides hole others typical causes. It is very important and amazing to discover and know physiology when you deal with OSAS patients.

When you say vocal fold activity, what do you mean. People can talk in both state REM and NREM sleep