The influence of warning signal timing and cognitive preparation on the aversiveness of electric shock

Emotional modulation of spinal nociception and pain: The impact of predictable noxious stimulation

Recent evidence suggests that emotional picture-viewing is a reliable method of engaging descending modulation of spinal nociception. The present study attempted to replicate these findings and determine the effect of noxious stimulus predictability. Participants viewed pictures from the International Affective Picture System (IAPS), during which pain and nociceptive flexion reflexes (NFR) were elicited by electric shocks delivered to the sural nerve. For half of the participants (n=25) shocks were preceded by a cue (predictable), whereas the other half received no cue (unpredictable). Results suggested emotion was successfully induced by pictures, but the effect of picture-viewing on the NFR was moderated by the predictability of the shocks. When shock was unpredictable, spinal nociception (NFR) and pain ratings were modulated in parallel. Specifically, pain and NFR magnitudes were lower during pleasant emotions and higher during unpleasant emotions. However, when shocks were predictable, only pain was modulated in this way. NFRs from predictable shocks were not altered by pictures. Further, exploratory analyses found that pain ratings, but not NFRs, were lower during predictable shocks. These data suggest emotional picture-viewing is a reliable method of engaging descending modulation of spinal nociception. However, descending modulation could not be detected in NFRs resulting from predictable noxious stimuli. Although preliminary, this study implies that separate mechanisms are responsible for emotional modulation of nociception at spinal vs. supraspinal levels, and that predictable noxious events may disengage modulation at the spinal level. The current paradigm could serve as a useful tool for studying descending modulation.

Sleep arousal response to experimental thermal stimulation during sleep in human subjects free of pain and sleep problems

Although the interaction between sleep and pain is generating considerable interest (NIH Technology Assessment Panel, 1996), it is still unknown if chronic pain is the cause or effect of poor sleep. To further this understanding, subjects free of pain and sleep problems need to be studied in order to assess their response to pain during sleep, defined as a behavioral and a physiological state in which sensory processing is altered. (For example, while auditory perception remains active, other sensory inputs are facilitated, attenuated, or suppressed (Velluti, 199746 degrees C) was statistically greater in the lighter sleep stage 2 (48.3%) than in the deeper stages 3&4 (27.9%). A nocifensive behavioral-motor response was associated with only 2.5% of the 351 heat pain stimuli. Two other markers of sleep quality-sleep stage shift and awakening-were not influenced by the thermal stimuli. None of the subjects demonstrated any burns in the morning following the thermal stimulations applied during sleep. We conclude that the processing of nociceptive inputs is attenuated across sleep stages.

The influence of film-induced mood on pain perception

It has been shown that a person's mood can influence pain tolerance. Films have been used as a means of inducing a desired mood. The effect on pain perception of film type and film length to induce mood was investigated. Previous research with brief humorous films had not indicated any unique advantage of humor over distraction approaches. Other recent research had indicated that after exposure to film stimulation there is a need to wait approximately 40 min before physiological changes can be obtained. Thus, the present study varied both film type and length and introduced a 30-min waiting period following the mood induction via film prior to exposure to cold-pressor pain. Two hundred subjects in nine different groups participated in the study. Three types of films were used: (1) humorous, (2) holocaust, (3) neutral. Three lengths of each type were also used: 15 min, 30 min, and 45 min. In addition, a tenth no-film group served as a control for the effects of a film. Each subject was given a baseline trial of cold-pressor pain, a trial immediately following the film and a trial 30 min later. Results indicated an advantage in increased pain tolerance for the humorous film and an increased pain tolerance for the longer film regardless of type only after the 30-min waiting period. Results were discussed from a pain theoretical perspective with emphasis placed on returning to psychological manipulations of the sensory aspects of pain and not just the cognitive/emotional/motivational dimensions.

The influence of warning signal timing and cognitive preparation on the aversiveness of cold-pressor pain

This study examined the role of prior warning time, cognitive preparation and self-efficacy in the reaction to cold-pressor pain that has a substantial stimulus duration and leaves a residual effect. Forty-eight, paid, male subjects were randomly assigned to one of 3 cognitive preparation groups: (1) Training group, provided with a self-instructional booklet of pain control techniques, (2) Citizenship group, to control for reading a booklet, and (3) Control group with no advanced preparation. Warning times used on a within-subjects basis were 0, 30, and 180 sec prior to immersion of their arms in cold water. Results indicated that overall, the 180 sec warning time yielded the lowest pain ratings. Warning time had no effect on duration in water for subjects who underwent training, but the 30 sec and 180 sec warning time yielded longer duration in water, for subjects in the other groups. The Training group preparation was effective in raising perceived self-efficacy for coping with pain which, in turn, was found to be correlated with pain tolerance. Perceived self-efficacy was also found to have an effect on heart rate with high scorers yielding a lower reaction upon immersion into the cold water compared to the low scorers. The results point to the need to consider the effect of the stimulus characteristics and the centrality of perceived self-efficacy when preparing a subject prior to pain stimulation.

Humor as a cognitive technique for increasing pain tolerance

Substantial research has demonstrated that cognitive psychological techniques including distraction can increase pain tolerance. In recent years, there also have been claims that humor and laughter possess unique characteristics for coping with pain and stress. Theoretically, explanations include the release of endorphins, the lowering of tension, as well as the distraction that results from humor. The question is whether humor is more effective than simple distraction. For this purpose humor was contrasted with a repulsive stimulus and a neutral stimulus controlled for interest level, that would also have distraction capabilities but not the unique aspects of humor. Pain tolerance was tested using cold pressor stimulation. Four groups (20 subjects in each) were tested. Three groups were shown a film: (1) a humorous film, (2) a repulsive film, (3) a neutral film. Group 4 was not shown any film. Results indicated that both the humor and repulsive groups showed a significant increase in pain tolerance as compared to the other groups. The repulsive group yielded the largest increase in pain tolerance although not different from the humor group. Except for sex differences, pain ratings did not show any group effects. Discussion focused on the type of distraction that would be meaningful for increasing pain tolerance and on the place of humor in pain control.

A dose-response study of the effects of intravenous midazolam on cold pressor-induced pain

The effects of intravenous midazolam (0.75, 1.5, and 3 mg/70 kg) were examined and compared to that of fentanyl (0.1 mg/70 kg; positive control) and saline on pain induced by a cold pressor test. Both sensory and affective components of the pain response were assessed, as there is some evidence that benzodiazepines reduce the affective component. Healthy volunteers (three females, nine males) were enrolled in a prospective, double-blind, randomized, cross-over trial in which mood and psychomotor performance were also examined. Five minutes and 135 min postinjection, subjects immersed their forearm in ice-cold water for 3 min while assessments of pain were recorded. During the first immersion, subjects reported significantly lower pain intensity and bothersomeness ratings after having been injected with fentanyl, relative to the saline and midazolam conditions, which did not differ significantly from each other. Fentanyl and midazolam had prototypical mood altering and psychomotor impairing effects. We conclude that midazolam in our laboratory setting at the doses and route of administration studied had no effects on either the sensory or affective components of the pain experience.