The Phenomenology of Pain During REM Sleep

Coarse — Pain in Dreams

Have you ever felt pain in dreams? I have. Once I dreamed I was lying on my stomach, getting a tattoo on my calf against my will. Because it was a particularly malevolent tattoo studio, I cried out in the dream. When I woke up, I felt no pain at all. It was false, a figment of the Pain Matrix. Another time a monkey bit me on the arm. Once again, the pain vanished upon awakening.

I think these examples of what I'll call "fake pain" are unusual. More common are instances when you get a calf cramp or have pins and needles in your arm while sleeping, and this real life pain gets incorporated into dreams about tattoos or monkey bites. But even these possibilities have been discounted as unlikely, because of limitations on which sensory modalities can be represented in dreams (Nielsen et al., 1993):

One possibility is that pain is beyond the representational capability of image formation processes -- that neither pain memories nor pain images are reproducible in the dreaming mode. A second possibility is that the sensory systems that might contribute to the representation of pain imagery are not functional during dreaming. This possibility is consistent with the finding that the high threshold polysynaptic afferent fibers that conduct pain sensations are actively inhibited during REM sleep in cats.

But plenty of people have reported feeling pain in dreams, so why construct hypotheses about why it's impossible? So skeptics Tore A. Nielsen and three fellow psychology graduate students, along with an undergrad art therapy student, conducted experiments on themselves in a 1993 paper. They inflated a blood pressure cuff above the knee of their colleagues 5 min into a bout of REM sleep¹ [to produce ischemia of the leg muscles, i.e. pins and needles or paralysis].

Results indicated that pain sensations occurred in 13 out of 42 stimulation trials with usable dream reports (31%). In contrast, only one of the 21 non-stimulated control dreams contained a reference to pain (4.8%). Many of the dreams were realistic and took place in a sleep lab-like setting. Others were more fantastic; one was set at a rodeo, another at a dance party in a barn [the authors lived in Montreal]. Some were lucid², like the "ugly shoe" dream:

I'm in a small store trying on a pair of ugly shoes. I started walking. Then I staggered forward because I was waking up and not fully conscious. You were laughing at me. I said "come on, its not funny, I'm trying to wake up!" This is the second or third time I've been trying to wake up.

Some of the participants were more likely to experience pain dreams than others. Subject B, who reported pain dreams on 70% of the stimulation trials, had knee surgery a few years prior and still felt numbness or tingling sensations on occasion. Most of the time, the pain sensations occurred in the appropriate leg for all participants. Interestingly, the "crampy pressure", "tingling", or "hurting a bit" sensations felt upon awakening were much less intense than those that occurred during the dream.

When interpreting these subjective reports, one has to consider an expectation or priming effect, since all the students were focused on dream research, with extensive experience in the sleep lab. However, this was not the case in a study of 28 hospitalized burn patients (Raymond et al., 2002). Obviously, the severity of suffering in burn patients is intense and chronic, unlike having temporary "pins and needles" in your leg. Over a period of 5 days, pain dreams comprised 30% of all reported dreams, which is quite comparable to the artificial BP cuff study. The patients who reported pain dreams (39%) had more nightmares, worse sleep quality, and more post-traumatic stress symptoms. The other 61% of the patients did not have any pain dreams. Why?

What sort of neurophysiological activity can account for painful sensations that are experienced during REM sleep? We'll find out in the next post.


Footnotes

¹ It wasn't clear how they monitored for REM, since EEG methods were not described. However, the transcript of one dream suggested that EEG was in fact recorded:

Then I was trying to get comfortable on the bed. All the electrodes but one for the EEG had fallen off; the others were dangling free.

The dream transcript continues:

You said that this was too bad. I had tossed around in bed trying to get comfortable. It was really cold and hurt my backside. There was almost no mattress; I was on a board. I was saying to you that we had hit rock bottom in this bed.

The interesting part about this segment is that there was no BP cuff applied; out of 14 dreams this was the only one without external stimulation (kind of like my "fake pain" dreams).

² The subject was aware they were dreaming and tried to control the action.


References

Nielsen TA, McGregor DL, Zadra A, Ilnicki D, & Ouellet L (1993). Pain in dreams. Sleep, 16 (5), 490-8 PMID: 7690981

Raymond I, Nielsen TA, Lavigne G, Choinière M. (2002). Incorporation of pain in dreams of hospitalized burn victims. Sleep 25:765-70.