1. "Researchers at New York University suggest that wakefulness and REM sleep are essentially similar brain states, differing only in the extent to which they are shaped by sensory stimuli from the outside world."

Brynie, Faith Hickman. 2006. Sleep and Dreams: 101 Questions about Sleep and Dreams. Minneapolis, MN: Twenty-First Century Books.

2. "...the present study describes experiences of dreamed pain that were reported incidentally in experiments on the effects of somatosensory stimulation administered during rapid eye movement (REM) sleep...Most often, these references appeared to be direct, untransformed incorporations of real sensations produced by stimulation. Pain was the principal motivating agent in a majority of these dreams and was in many cases associated with strong emotion--typically anger. Dreams often depicted the subjects' attempts to obtain relief from pain, in some cases by repetition of actions, in others by metaphoric renditions of the goal. The results indicate that although pain is rare in dreams, it is nevertheless compatible with the representational code of dreaming."

Nielsen TA et al. 1993. Pain in dreams. Sleep. Aug;16(5):490-8.