Despite myriad challenges, clinicians see room for progress.
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Edited by Howard L. Fields, University of California, San Francisco, CA, and accepted by the Editorial Board April 22, 2015 (received for review March 5, 2015)
Article Figures & SI
Figures
- Fig. 1.
Stimulus parameters and experimental design. The conditioning procedure (COND) included images of two male faces (conditional cues) presented on a computer screen. Human faces used with permission from KDEF. Each face cue was consistently paired with either a high or low heat pain stimulus on the volar forearm. After conditioning, a test sequence was performed (TEST) in which the High cue, the Low cue, and a neutral Control cue were paired with identical moderate heat stimuli. Subliminal images were shown by means of masked faces, and supraliminal images were shown unmasked. Faces were exposed for 12 ms during masked trials (followed by an 84-ms mask) and for 100 ms during unmasked trials. Participants were randomly assigned to one of four combinations of subliminal/supraliminal conditioning and subliminal/supraliminal test sequence.
- Fig. 2.
Pain ratings during subliminal and supraliminal analgesia and hyperalgesia trials. Identical moderate temperatures were paired with a conditioned High Pain cue, Low Pain cue, or Control cue to test how predictive cues changed participants’ pain perception. Participants rated pain intensity on a 0–100 NRS. (Left) Representation of pain ratings during the test sequence that followed the initial conditioning sequence. Bars represent the average pain rating in response to identical moderate temperatures. Error bars represent 2 intrasubject SEs. The P value (P < 0.001) reflects the main effect for cue type across all experimental groups. (Right) Illustration of the interaction of cue type (High, Low, Control) by experimental group (A, B, C, and D). P values reflect the pairwise comparisons between cue types across experimental groups (High–Control, Low–Control, High–Low).
Tables
Variable Group A Group B Group C Group D Age 25.1 (5.2) 25.9 (4.7) 29.5 (10.1) 25.0 (5.2) Male/female ratio, M/F% 39/61 36/64 58/42 27/73 High pain temperature (calibrated), °C 47.5 (1.1) 47.1 (1.5) 47.1 (1.4) 47.5 (1.6) Low pain temperature (fixed), °C 44.5 (1.1) 44.1 (1.5) 44.1 (1.4) 44.5 (1.6) Moderate pain temperature (fixed), °C 46.0 (1.1) 45.6 (1.5) 45.6 (1.4) 46.0 (1.6) Pain rating, high temperature (NRS) 51.7 (20) 51.4 (16.5) 53.8 (17) 55.9 (19) Pain rating, low temperature (NRS) 11.6 (9.5) 18.8 (18) 18.3 (12.2) 14.2 (13) Calibrated high pain temperatures represent the temperature at which each participant rated pain around 60 on a 0–100 pain NRS. Low pain temperatures were set as 3 °C below the calibrated high pain temperature (fixed), and moderate pain was set as the temperature right in between high and low pain (fixed). Pain ratings (0–100 NRS) are from the conditioning phase, when tailored high and low temperatures were used. Values represent group means and SDs.
- Table 2.
Pairwise comparisons of test sequence pain ratings with Bonferroni adjustments for multiple comparisons
Comparison Mean difference (SD) t P 95% confidence interval Cohen’s dz High–Control 5.21 (7.42) 4.82 0.00003 2.65–7.96 0.70 Control–Low 1.53 (2.73) 3.84 0.0009 0.57–2.53 0.56 High–Low 6.75 (7.88) 5.87 0.000001 3.98–9.72 0.86
Conditioning without awareness
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- Psychological and Cognitive Sciences
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