Fig 1.
Time course of experimental events: Stimuli were administered in four separate experimental blocks: familiarization, calibration, conditioning, and testing.
Treatment (clonidine for REMSDs (n = 13) or placebo for control pill group (n = 13)) was given immediately before going to bed. Famil: familiarization, Calib: calibration.
Table 1.
Polysomnographic parameters for both groups (mean ± standard error of the mean).
Two-sided Kruskal—Wallis tests or two-sided ANOVAs were used according to the normal distribution of the variable.
Fig 2.
Expected pain A) intensity and B) unpleasantness measured in the morning at control and placebo test sites before placebo testing block for REMSDs and Controls. Statistical analyses revealed no group effect for expected pain intensity or unpleasantness (REMSDs vs. Controls, p = 0.501 and 0.126), but a stimulation site effect was found (control vs. placebo sites: p < 0.001 and p < 0.001) with no interaction (p = 0.761 and 0.415). Analysis of expected pain intensity (C) and unpleasantness (D) between placebo and control test sites revealed no significant between-group difference (p = 0.927 and p = 0.276) (mean ± standard error of the mean). Subjective assessments of pain intensity and unpleasantness were obtained by visual analog scale (VAS, 0–100).
Fig 3.
Concurrent pain A) intensity and B) unpleasantness measured in the morning at control and placebo sites for REMSDs and Controls. Statistical analyses revealed a group effect for concurrent pain intensity and unpleasantness (REMSDs vs. Controls, p = 0.028 and 0.030), a stimulation site effect (control vs. placebo sites: p < 0.001 and p < 0.001), and an interaction (*: p = 0.006 and 0.030). Analysis of concurrent pain intensity (C) and unpleasantness (D) between placebo and control sites revealed a significant between-group difference (p = 0.006 and p = 0.030) (mean ± standard error of the mean). 1 to 5 depict stimulations 1 to 5. Subjective assessments of pain intensity and unpleasantness were obtained by visual analog scale (VAS, 0–100).
Fig 4.
Remembered pain A) intensity and B) unpleasantness measured in the morning at control and placebo sites for REMSDs and Controls. Statistical analyses revealed a group effect for concurrent pain intensity and unpleasantness (REMSDs vs. Controls, p = 0.028 and 0.030), a stimulation site effect (control vs. placebo test sites: p < 0.001 and p < 0.001), and an interaction (p = 0.006 and 0.030). Analysis of remembered pain intensity (C) and unpleasantness (D) between placebo and control sites revealed a significant between-group difference (p = 0.002) for pain intensity, but not for unpleasantness (p = 0.070) (mean ± standard error of the mean). Subjective assessments of pain intensity and unpleasantness were obtained using visual analog scale (VAS, 0–100).
Table 2.
Results of the moderation analysis testing the effect of REM (M) on the relationship between expected (X) and placebo (Y) analgesia.
Table 3.
Psychomotor vigilance task and questionnaires administered in the evening and morning for both groups (mean ± standard error of the mean).
Two-sided ANOVAs were used.
Table 4.
Blood pressure measurements in the evening and morning for both groups (SBP: systolic blood pressure, DBP: diastolic blood pressure, mean ± standard error of the mean).
Two-sided ANOVAs were used.