Several years ago, my attempts to go to sleep were often sabotaged by words flashing in neon green in the right side of my head. All the words started with a "z" like zonk, zip, zap, zoom and sometimes they were accompanied by the sensation these words were shouted at me. They would violently wrench me awake. But I never discussed it with my therapist or doctor.
Yes, it would be interesting to know the scientific explanation.
Carolyn