High-Anxious People Generalize Costly Pain-Related Avoidance Behavior More to Novel Safe Contexts Compared to Low-Anxious People.

Pain-related avoidance is adaptive when there is a bodily threat, but when it generalizes to safe movements/situations, it may become disabling. Both subclinical anxiety-a vulnerability marker for chronic pain-and chronic pain are associated with excessive fear generalization to safe stimuli/situations. Previous research focused mainly on passive fear correlates (psychophysiological arousal and self-reports) leaving avoidance behavior poorly understood. Therefore, we tested whether high-anxious individuals generalize their pain-related avoidance behavior more to novel, safe contexts than low-anxious people. In a robotic-arm-reaching task, both groups (low vs high trait anxiety) performed 1 of 3 movements to reach a target. In the threat context (black background), a painful stimulus could be partly/completely prevented by performing more effortful trajectories (longer and more force needed); in the safe context (white background), no pain occurred. Generalization of avoidance was tested in 2 novel contexts (light/dark gray backgrounds). We assessed pain expectancy, pain-related fear, startle eyeblink responses for all trajectories, and avoidance behavior (ie, maximal deviation from shortest trajectory). Results indicated that differential fear and expectancy selectively generalized to the novel context resembling the original threat context in both groups. Interestingly and in contrast with the verbal reports, high-anxious participants avoided more in the novel context resembling the original safe context, but not in the 1 resembling the threat context. No generalization emerged in the startle data. Because excessive pain-related avoidance specifically may cause withdrawal from daily life activities, these findings suggest that high-anxious individuals may be vulnerable to developing chronic pain disability. PERSPECTIVE: This paper shows that high-anxious people do not overgeneralize pain-related fear and pain expectancy learned in a threat context more to novel, safe contexts than low-anxious individuals, but that they do avoid more in those contexts. These findings suggest that high-anxious individuals may be vulnerable to developing chronic pain disability.

Error Processing and Pain: A New Perspective.

Errors put organisms in danger. Upon error commission, error processing allows for the updating of behavior that proved ineffective in light of the current context and goals, and for the activation of behavioral defensive systems. Pain, on the other hand, signals actual or potential danger to one's physical integrity and, likewise, motivates protective behavior. These parallels suggest the existence of cross-links between pain and error processing but so far their relationship remains elusive. In this review, we tie together findings from the field of pain research with those from electroencephalography studies on error processing [specifically the Error Related Negativity (ERN) and Positivity (Pe)]. More precisely, we discuss 3 plausible associations: Firstly, pain may enhance error processing as it increases error salience. Secondly, persons fearful of pain may be particularly vigilant towards painful errors and thus show a stronger neural response to them. Thirdly, the ERN as a component of the neural response to error commission is considered an endophenotype of threat sensitivity. As high sensitivity to pain threats is known to incite avoidance behavior, this raises the intriguing possibility that neural signatures of error processing predict pain-related protective behaviors, such as avoidance. We propose an integration of these findings into a common framework to inspire future research. PERSPECTIVE: Inspired by research in anxiety disorders, we discuss the potential bi-directional relationships between error processing and pain, and identify future directions to examine the neural and psychological processes involved in acute and chronic pain and respective avoidance behavior.

Pain by mistake: investigating a link between error-related negativity and pain avoidance behavior.

ABSTRACT: Pain can be considered as a signal of "bodily error": errors put organisms at danger and activate behavioral defensive systems. If the error is of physical nature, pain is the warning signal that motivates protective action such as avoidance behavior to safeguard our body's integrity. Interestingly, an important component of neural error processing, the error-related negativity (ERN), has been found to be related to avoidance in anxiety disorders. The present study is the first to extend these findings to pain and investigate the relationship between ERN and pain-related avoidance behavior. It was hypothesized that individuals with larger ERN amplitudes would show more pain-related avoidance behavior and would be more persistent in their avoidance despite changes in the environment. Fifty-three healthy individuals performed the Eriksen flanker task during which their brain activity on correct and erroneous motor responses was recorded by means of high-density electroencephalography. Avoidance behavior was assessed with an arm reaching task using the HapticMaster robot arm. The results showed that, in contrast to our hypothesis, avoidance was not related to ERN amplitudes. Surprisingly, persons with elevated ERN amplitudes showed low levels of avoidance specifically during early acquisition trials. In contrast to earlier findings in anxiety disorders, individuals with elevated ERN amplitudes did not engage in more pain-related avoidance behavior. In fact, the opposite pattern was found at the start of acquisition: individuals with higher compared with lower ERN amplitudes were slower in learning to avoid pain. Replications and future studies on the relationship between ERN and avoidance behavior are needed.

Modulating pain thresholds through classical conditioning.

BACKGROUND: Classical conditioning has frequently been shown to be capable of evoking fear of pain and avoidance behavior in the context of chronic pain. However, whether pain itself can be conditioned has rarely been investigated and remains a matter of debate. Therefore, the present study investigated whether pain threshold ratings can be modified by the presence of conditioned non-nociceptive sensory stimuli in healthy participant. METHODS: In 51 healthy volunteers, pain threshold to electrocutaneous stimuli was determined prior to participation in a simultaneous conditioning paradigm. Participants underwent an acquisition phase in which one non-painful vibrotactile stimulus (CS+) was repeatedly paired with a painful electrocutaneous stimulus, whereas a second vibrotactile stimulus of the same quality and intensity (CS-) was paired with a non-painful electrocutaneous stimulus. Stimulation was provided on the lower back with close proximity between the conditioned stimulus and the unconditioned stimulus. In the test phase, electrocutaneous stimuli at the individually-set threshold intensity were simultaneously delivered together with either a CS+ or CS-. Pain intensity ratings were obtained after each trial; expectancy ratings were obtained after each block. The primary outcome was the percentage of test stimuli that were rated as painful. RESULTS: Test stimuli were more likely to be rated as painful when they were paired with the CS+ than when they were paired with the CS-. This effect was not influenced by contingency awareness, nor by expectancies or mood states. DISCUSSION: The findings support the notion that the judgement of an event being painful or non-painful can be influenced by classical conditioning and corroborate the possible role of associative learning in the development and maintenance of chronic pain.

Interpretation bias in the face of pain: a discriminatory fear conditioning approach.

Background and aims Interpreting pain- and illness-related stimuli as health-threatening is common among chronic pain patients but also occurs in the general population. As interpretation bias (IB) may affect pain perception and might even play part in the development and maintenance of chronic pain, it is important to improve our understanding of this concept. Several studies suggest an association between IB and pain-related anxiety. However, those studies often rely on verbal and pictorial IB tasks that do not entail a threat of actual pain, therefore lacking personal relevance for healthy participants. The current study investigated whether healthy individuals show an IB towards ambiguous health-related stimuli in a context of actual pain threat, and explored whether this bias is associated to pain anxiety constructs. Methods Thirty-six healthy participants were conditioned to expect painful electrocutaneous shocks (unconditioned stimulus - US) after health-threat words (CS+) but not after neutral (non-health-threat) words (CS-) in order to establish fear of pain. Subsequently, they completed a verbal interpretation task that contained new CS+ and CS- stimuli as well as ambiguous non-reinforced health-threat and non-health-threat words. IB was assessed through shock expectancy ratings and startle responses to ambiguous and evident health threatening or neutral word stimuli. Pain-related anxiety was measured with validated questionnaires. Results The results show a general IB towards ambiguous health-related words on pain expectancies but not on startle response. An exploratory analysis suggests that this effect exists irrespective of pain-related anxiety levels which however may be due to a lack of power. Conclusion We present a novel experimental paradigm employing actual health threat that captures IB towards health-related stimuli in healthy individuals. Taken together, results provide evidence for the further consideration of IB as a latent vulnerability factor in the onset and maintenance of pain chronicity. In contrast to previous studies employing a safe, pain-free context, we found that healthy participants show an IB towards ambiguous health-related stimuli, when confronted with pain threat. Implications Like chronic pain patients, healthy individuals display an IB towards health-threat stimuli when these stimuli become personally relevant by carrying information about pending health threat. Therefore, the presented paradigm could be valuable for pain-related cognitive bias research in healthy participants as it may have a higher ecological validity than previous study designs. Future studies will have to elucidate the influence of anxiety constructs on IB in larger samples.

General versus pain-specific cognitions: Pain catastrophizing but not optimism influences conditioned pain modulation.

BACKGROUND: Previous studies found evidence that dispositional optimism is related to lower pain sensitivity. Recent findings suggest that temporarily increasing optimism by means of imagining a positive future may also have pain-alleviating effects. OBJECTIVES: The present experiment was designed to investigate conditioned pain modulation (CPM) as a potential underlying mechanism of this pain-alleviating effect of induced optimism. METHODS: For this purpose, 45 healthy participants were randomized into an optimistic or neutral imagery condition. Additionally, participants completed questionnaires on dispositional optimism, pain catastrophizing and pain expectations. CPM was assessed by delivering a series of five heat pain stimuli on the nondominant hand before and during immersion of the dominant hand in water of 5°C for 70 s. RESULTS: A clear CPM effect was found, that is heat pain reports were lower during simultaneous cold water stimulation. Although the optimism manipulation successfully increased optimism, it did not affect pain ratings or CPM. Post hoc analyses indicated that dispositional optimism was not associated with the magnitude of CPM, but pain catastrophizing and pain expectations did significantly correlate with the CPM effect. CONCLUSION: Pain-specific but not general cognitions appear to influence endogenous pain modulation. SIGNIFICANCE: Conditioned pain modulation is not the underlying mechanism of the pain-alleviating effects of induced optimism. However, pain-specific cognitions including pain catastrophizing and pain expectations affect endogenous pain modulation which should be taken into account in treatment and CPM research.

The Influence of Executive Functioning on Facial and Subjective Pain Responses in Older Adults.

Cognitive decline is known to reduce reliability of subjective pain reports. Although facial expressions of pain are generally considered to be less affected by this decline, empirical support for this assumption is sparse. The present study therefore examined how cognitive functioning relates to facial expressions of pain and whether cognition acts as a moderator between nociceptive intensity and facial reactivity. Facial and subjective responses of 51 elderly participants to mechanical stimulation at three intensities levels (50 kPa, 200 kPa, and 400 kPa) were assessed. Moreover, participants completed a neuropsychological examination of executive functioning (planning, cognitive inhibition, and working memory), episodic memory, and psychomotor speed. The results showed that executive functioning has a unique relationship with facial reactivity at low pain intensity levels (200 kPa). Moreover, cognitive inhibition (but not other executive functions) moderated the effect of pressure intensity on facial pain expressions, suggesting that the relationship between pressure intensity and facial reactivity was less pronounced in participants with high levels of cognitive inhibition. A similar interaction effect was found for cognitive inhibition and subjective pain report. Consequently, caution is needed when interpreting facial (as well as subjective) pain responses in individuals with a high level of cognitive inhibition.