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Inverted Perceptual Judgment of Nociceptive Stimuli at Threshold Level following Inconsistent Cues.

Walter C, Dimova V, Bu J, Parnham MJ, Oertel BG, Lötsch J - PLoS ONE (2015)

Bottom Line: The random and often incorrect announcement of stimuli clearly below or above pain threshold caused the subjects to rate the stimuli at pain-threshold level in the opposite direction of the cue, i.e., when the stimuli were announced as "pain" significantly more often than as non-painful and vice versa (p < 10(-4)).The present study revealed the induction of associations incongruent with a given message in the perception of pain.These findings are consistent with reported data on the effects of distrust on non-painful cognitive responses.

View Article: PubMed Central - PubMed

Affiliation: Institute of Clinical Pharmacology, Goethe-University, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany.

ABSTRACT

Objective: The perception of pain is susceptible to modulation by psychological and contextual factors. It has been shown that subjects judge noxious stimuli as more painful in a respective suggestive context, which disappears when the modifying context is resolved. However, a context in which subjects judge the painfulness of a nociceptive stimulus in exactly the opposite direction to that of the cues has never been shown so far.

Methods: Nociceptive stimuli (300 ms intranasal gaseous CO2) at the individual pain threshold level were applied after a visual cue announcing the stimulus as either "no pain", merely a "stimulus", or "pain". Among the stimuli at threshold level, other CO2 stimuli that were clearly below or above pain threshold were randomly interspersed. These were announced beforehand in 12 subjects randomly with correct or incorrect cues, i.e., clearly painful or clearly non-painful stimuli were announced equally often as not painful or painful. By contrast, in a subsequent group of another 12 subjects, the stimuli were always announced correctly with respect to the evoked pain.

Results: The random and often incorrect announcement of stimuli clearly below or above pain threshold caused the subjects to rate the stimuli at pain-threshold level in the opposite direction of the cue, i.e., when the stimuli were announced as "pain" significantly more often than as non-painful and vice versa (p < 10(-4)). By contrast, in the absence of incongruence between announcement and perception of the far-from-threshold stimuli, stimuli at pain threshold were rated in the cued direction.

Conclusions: The present study revealed the induction of associations incongruent with a given message in the perception of pain. We created a context of unreliable cues whereby subjects perceived the stimulus opposite to that suggested by a prior cue, i.e., potentially nociceptive stimuli at pain threshold level that were announced as painful were judged as non-painful and vice versa. These findings are consistent with reported data on the effects of distrust on non-painful cognitive responses.

No MeSH data available.


Related in: MedlinePlus

Graphical scheme of the experimental settings applied in either group 1 (top bars) or group 2 (bottom bars) subjects.The paradigm applied to either group is shown in each two lines of differently colored small bars of which each denotes a CO2 stimulus and the associated cues. Specifically, in the upper lines, the CO2 stimuli are shown in their chronological succession differently colored for 25% v/v CO2 stimuli (green), CO2 concentration at the individual pain threshold level (grey) and 75% v/v CO2 (red). Below each stimulus, in the second line the cues given before stimulus application are denoted as “No pain” (green), “Stimulus”, i.e., a neutral cue (grey) and “Pain” (red). In the first group, the far-from-thresholds stimuli were cued randomly, i.e., green and red bars in lines 1 and 2 are mixed, whereas in the second group, the 25 and 75% stimuli were always preceded by correct cues, which can be seen by the consistent agreement between green or red bars in lines 1 and 2. The inequality of the experimental settings between the groups is commented on in the discussion of this paper.
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pone.0132069.g001: Graphical scheme of the experimental settings applied in either group 1 (top bars) or group 2 (bottom bars) subjects.The paradigm applied to either group is shown in each two lines of differently colored small bars of which each denotes a CO2 stimulus and the associated cues. Specifically, in the upper lines, the CO2 stimuli are shown in their chronological succession differently colored for 25% v/v CO2 stimuli (green), CO2 concentration at the individual pain threshold level (grey) and 75% v/v CO2 (red). Below each stimulus, in the second line the cues given before stimulus application are denoted as “No pain” (green), “Stimulus”, i.e., a neutral cue (grey) and “Pain” (red). In the first group, the far-from-thresholds stimuli were cued randomly, i.e., green and red bars in lines 1 and 2 are mixed, whereas in the second group, the 25 and 75% stimuli were always preceded by correct cues, which can be seen by the consistent agreement between green or red bars in lines 1 and 2. The inequality of the experimental settings between the groups is commented on in the discussion of this paper.

Mentions: The cues were given randomly, i.e., both the 25% v/v and the 75% v/v CO2 stimuli were randomly announced as “no pain”, neutral (“stimulus”) or “pain” (n = 5 per condition; group 1; for details, see Fig 1), meaning that several of the 75% CO2 stimuli were announced as non-painful, despite their clear painfulness, and several of the 25% CO2 stimuli were announced as painful, although the evoked pricking sensations were clearly below the pain threshold. This paradigm served to create a context of questioning the cues thus arousing mistrust. The details of the stimulation and cue paradigm are shown in Fig 1 (top). To interpret the results, a second group (group 2) was assessed. In this group, the 25 and 75% CO2 stimuli were always announced correctly, i.e., the 25% v/v stimuli were announced as “no pain” and the 75% v/v stimuli as “pain”. This paradigm excluded the application of the neutral cue for the far from pain thresholds stimuli. Thus, the total number of stimuli for group 1 was 45 stimuli (15 threshold stimuli and 15 far-below and far-above threshold stimuli, respectively), whereas subjects of group 2 received 63 stimuli (45 threshold stimuli and nine far-below and far-above threshold stimuli, respectively). For this reason and also due to the sequential performance of the study, the stimulation paradigms differed between groups (Fig 1), which finally posed some problems in the interpretation of the causes underlying the present observations that will be addressed in the discussion to this paper. The main experiments lasted 23 min in the first and 30 min in the second group.


Inverted Perceptual Judgment of Nociceptive Stimuli at Threshold Level following Inconsistent Cues.

Walter C, Dimova V, Bu J, Parnham MJ, Oertel BG, Lötsch J - PLoS ONE (2015)

Graphical scheme of the experimental settings applied in either group 1 (top bars) or group 2 (bottom bars) subjects.The paradigm applied to either group is shown in each two lines of differently colored small bars of which each denotes a CO2 stimulus and the associated cues. Specifically, in the upper lines, the CO2 stimuli are shown in their chronological succession differently colored for 25% v/v CO2 stimuli (green), CO2 concentration at the individual pain threshold level (grey) and 75% v/v CO2 (red). Below each stimulus, in the second line the cues given before stimulus application are denoted as “No pain” (green), “Stimulus”, i.e., a neutral cue (grey) and “Pain” (red). In the first group, the far-from-thresholds stimuli were cued randomly, i.e., green and red bars in lines 1 and 2 are mixed, whereas in the second group, the 25 and 75% stimuli were always preceded by correct cues, which can be seen by the consistent agreement between green or red bars in lines 1 and 2. The inequality of the experimental settings between the groups is commented on in the discussion of this paper.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493070&req=5

pone.0132069.g001: Graphical scheme of the experimental settings applied in either group 1 (top bars) or group 2 (bottom bars) subjects.The paradigm applied to either group is shown in each two lines of differently colored small bars of which each denotes a CO2 stimulus and the associated cues. Specifically, in the upper lines, the CO2 stimuli are shown in their chronological succession differently colored for 25% v/v CO2 stimuli (green), CO2 concentration at the individual pain threshold level (grey) and 75% v/v CO2 (red). Below each stimulus, in the second line the cues given before stimulus application are denoted as “No pain” (green), “Stimulus”, i.e., a neutral cue (grey) and “Pain” (red). In the first group, the far-from-thresholds stimuli were cued randomly, i.e., green and red bars in lines 1 and 2 are mixed, whereas in the second group, the 25 and 75% stimuli were always preceded by correct cues, which can be seen by the consistent agreement between green or red bars in lines 1 and 2. The inequality of the experimental settings between the groups is commented on in the discussion of this paper.
Mentions: The cues were given randomly, i.e., both the 25% v/v and the 75% v/v CO2 stimuli were randomly announced as “no pain”, neutral (“stimulus”) or “pain” (n = 5 per condition; group 1; for details, see Fig 1), meaning that several of the 75% CO2 stimuli were announced as non-painful, despite their clear painfulness, and several of the 25% CO2 stimuli were announced as painful, although the evoked pricking sensations were clearly below the pain threshold. This paradigm served to create a context of questioning the cues thus arousing mistrust. The details of the stimulation and cue paradigm are shown in Fig 1 (top). To interpret the results, a second group (group 2) was assessed. In this group, the 25 and 75% CO2 stimuli were always announced correctly, i.e., the 25% v/v stimuli were announced as “no pain” and the 75% v/v stimuli as “pain”. This paradigm excluded the application of the neutral cue for the far from pain thresholds stimuli. Thus, the total number of stimuli for group 1 was 45 stimuli (15 threshold stimuli and 15 far-below and far-above threshold stimuli, respectively), whereas subjects of group 2 received 63 stimuli (45 threshold stimuli and nine far-below and far-above threshold stimuli, respectively). For this reason and also due to the sequential performance of the study, the stimulation paradigms differed between groups (Fig 1), which finally posed some problems in the interpretation of the causes underlying the present observations that will be addressed in the discussion to this paper. The main experiments lasted 23 min in the first and 30 min in the second group.

Bottom Line: The random and often incorrect announcement of stimuli clearly below or above pain threshold caused the subjects to rate the stimuli at pain-threshold level in the opposite direction of the cue, i.e., when the stimuli were announced as "pain" significantly more often than as non-painful and vice versa (p < 10(-4)).The present study revealed the induction of associations incongruent with a given message in the perception of pain.These findings are consistent with reported data on the effects of distrust on non-painful cognitive responses.

View Article: PubMed Central - PubMed

Affiliation: Institute of Clinical Pharmacology, Goethe-University, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany.

ABSTRACT

Objective: The perception of pain is susceptible to modulation by psychological and contextual factors. It has been shown that subjects judge noxious stimuli as more painful in a respective suggestive context, which disappears when the modifying context is resolved. However, a context in which subjects judge the painfulness of a nociceptive stimulus in exactly the opposite direction to that of the cues has never been shown so far.

Methods: Nociceptive stimuli (300 ms intranasal gaseous CO2) at the individual pain threshold level were applied after a visual cue announcing the stimulus as either "no pain", merely a "stimulus", or "pain". Among the stimuli at threshold level, other CO2 stimuli that were clearly below or above pain threshold were randomly interspersed. These were announced beforehand in 12 subjects randomly with correct or incorrect cues, i.e., clearly painful or clearly non-painful stimuli were announced equally often as not painful or painful. By contrast, in a subsequent group of another 12 subjects, the stimuli were always announced correctly with respect to the evoked pain.

Results: The random and often incorrect announcement of stimuli clearly below or above pain threshold caused the subjects to rate the stimuli at pain-threshold level in the opposite direction of the cue, i.e., when the stimuli were announced as "pain" significantly more often than as non-painful and vice versa (p < 10(-4)). By contrast, in the absence of incongruence between announcement and perception of the far-from-threshold stimuli, stimuli at pain threshold were rated in the cued direction.

Conclusions: The present study revealed the induction of associations incongruent with a given message in the perception of pain. We created a context of unreliable cues whereby subjects perceived the stimulus opposite to that suggested by a prior cue, i.e., potentially nociceptive stimuli at pain threshold level that were announced as painful were judged as non-painful and vice versa. These findings are consistent with reported data on the effects of distrust on non-painful cognitive responses.

No MeSH data available.


Related in: MedlinePlus