Effects of explicit cueing and ambiguity on the anticipation and experience of a painful thermal stimulus

Abstract

Many factors can influence the way in which we perceive painful events and noxious stimuli, but less is known about how pain perception is altered by explicit knowledge about the impending sensation. This study aimed to investigate the impact of explicit cueing on anxiety, arousal, and pain experience during the anticipation and delivery of noxious thermal heat stimulations. Fifty-two healthy volunteers were randomised to receive explicit instructions about visual cue-stimulus temperature pairings, or no explicit instructions about the cue-stimulus pairs. A pain anxiety task was used to investigate the effects of explicit cueing on anticipatory anxiety, pain experience and electrophysiological responses. Participants who received explicit instructions about the cue-stimulus pairs (i.e., the relationship between the colour of the cue and the temperature of the associated stimuli) reported significantly higher subjective anxiety prior to the delivery of the thermal heat stimuli (p = .025, partial eta squared = .10). There were no effects of explicit cueing on subsequent pain intensity, unpleasantness, or the electrophysiological response to stimulus delivery. The perceived intensity and unpleasantness of the stimuli decreased across the blocks of the paradigm. In both groups anticipating the ambiguous cue elicited the largest change in electrophysiological arousal, indicating that not knowing the impending stimulus temperature led to increased arousal, compared to being certain of receiving a high temperature thermal stimulus (both p < .001). Perceived stimulus intensity varied between ambiguous and non-ambiguous cues, depending on the temperature of the stimulus. Together these findings highlight the impact and importance of explicit cueing and uncertainty in experimental pain studies, and how these factors influence the way healthy individuals perceive and react to noxious and innocuous thermal stimuli.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1. Trial design for the pain anxiety task.

Note that although the duration of the stimulus in Fig 1 is listed as four seconds, this includes one second for the thermode to increase from the baseline temperature to the target temperature, and an additional second for the thermode to return to the baseline temperature following the two second application of the stimulus at the target temperature. A 0.5s ‘beep’ signalled the commencement of thermal stimulus delivery. After each stimulus was delivered participants were prompted to provide ratings of anticipatory anxiety, pain intensity, and pain unpleasantness.

Fig 2. Subjective anxiety ratings (CUE x GROUP interaction).

(A) “Hint” participants, and (B) “No Hint” participants. The Purple cue always preceded a 45°C stimulus, the Orange cue always preceded a 41°C stimulus, the Pink cue always preceded a 32°C stimulus, and the Blue cue always preceded an ambiguous stimulus. Data presented as mean (standard error). * p < .05.

Fig 3. Subjective anxiety ratings (CUE x BLOCK) interaction.

(A) Purple cue (always preceded a 45°C stimulus), (B) Orange cue (always preceded a 41°C stimulus), (C) Pink cue (always preceded a 32°C stimulus), and (D) Blue cue (always preceded a stimulus of ambiguous temperature). Data presented as mean (standard error). * p < .05.

Fig 4. Anticipatory electrophysiological changes during cue presentation.

(A) Heart rate change, and (B) Skin conductance response change. The Purple cue always preceded a 45°C stimulus, the Orange cue always preceded a 41°C stimulus, the Pink cue always preceded a 32°C stimulus, and the Blue cue always preceded an ambiguous stimulus. Data presented as mean (standard error). * p < .001.

Fig 5. Anticipatory skin conductance response change (CUE x BLOCK) interaction.

(A) Purple cue (always preceded a 45°C stimulus), (B) Orange cue (always preceded a 41°C stimulus), (C) Pink cue (always preceded a 32°C stimulus), and (D) Blue cue (always preceded a stimulus of ambiguous temperature). Data presented as mean (standard error). * p < .05.

Fig 6. Subjective ratings of pain intensity (NATURE x TEMPERATURE x BLOCK).

(A) Ratings for thermal stimuli preceded by non-ambiguous cues, and (B) ratings for thermal stimuli preceded by ambiguous cues. Ratings provided in Block 1 are represented by black bars, ratings provided in Block 2 are represented by grey bars, while ratings provided in Block 3 are represented by white bars. Data presented as mean (standard error). * p < .05.

Fig 7. Subjective ratings of pain unpleasantness (NATURE x TEMPERATURE x BLOCK).

(A) Ratings for thermal stimuli preceded by non-ambiguous cues, and (B) ratings for thermal stimuli preceded by ambiguous cues. Ratings provided in Block 1 are represented by black bars, ratings provided in Block 2 are represented by grey bars, while ratings provided in Block 3 are represented by white bars. Data presented as mean (standard error). * p < .05.