Distraction produces an increase in pain-evoked anterior cingulate activity

The dynamics of pain reappraisal: the joint contribution of cognitive change and mental load

This study was designed to investigate the neural mechanism of cognitive modulation of pain via a reappraisal strategy with high temporal resolution. The EEG signal was recorded from 29 participants who were instructed to down-regulate, up-regulate, or maintain their pain experience. The L2 minimum norm source reconstruction method was used to localize areas in which a significant effect of the instruction was present. Down-regulating pain by reappraisal exerted a robust effect on pain processing from as early as ~100 ms that diminished the activity of limbic brain regions: the anterior cingulate cortex, right orbitofrontal cortex, left anterior temporal region, and left insula. However, compared with the no-regulation condition, the neural activity was similarly attenuated in the up- and down-regulation conditions. We suggest that this effect could be ascribed to the cognitive load that was associated with the execution of a cognitively demanding reappraisal task that could have produced a general attenuation of pain-related areas regardless of the aim of the reappraisal task (i.e., up- or down-regulation attempts). These findings indicate that reappraisal effects reflect the joint influence of both reappraisal-specific (cognitive change) and unspecific (cognitive demand) factors, thus pointing to the importance of cautiously selected control conditions that allow the modulating impact of both processes to be distinguished.

Spinal and supraspinal modulation of pain responses by hypnosis, suggestions, and distraction

The mechanisms underlying pain modulation by hypnosis and the contribution of hypnotic induction to the efficacy of suggestions being still under debate, our study aimed, (1) to assess the effects of identical hypoalgesia suggestions given with and without hypnotic induction, (2) to compare hypnotic hypoalgesia to distraction hypoalgesia and (3) to evaluate whether hypnotic suggestions of increased and decreased pain share common psychophysiological mechanisms. To this end, pain ratings, nociceptive flexion reflex amplitude, autonomic responses and electroencephalographic activity were measured in response to noxious electrical stimulation of the sural nerve in 20 healthy participants, who were subjected to four conditions: suggestions of hypoalgesia delivered with and without hypnosis induction (i.e. hypnotic-hypoalgesia and suggested-hypoalgesia), distraction by a mental calculation task and hypnotic suggestions of hyperalgesia. As a result, pain ratings decreased in distraction, suggested-hypoalgesia and hypnotic-hypoalgesia, while it increased in hypnotic-hyperalgesia. Nociceptive flexion reflex amplitude and autonomic activity decreased during suggested-hypoalgesia and hypnotic-hypoalgesia but increased during distraction and hypnotic-hyperalgesia. Hypnosis did not enhance the effects of suggestions significantly in any measurement. No somatosensory-evoked potential was modulated by the four conditions according to strict statistical criteria. The absence of a significant difference between the hypnotic hypoalgesia and hyperalgesia conditions suggests that brain processes as evidenced by evoked potentials are not invariably related to pain modulation. Time-frequency analysis of electroencephalographic activity showed a significant differentiation between distraction and hypnotic hypoalgesia in the theta domain. These results highlight the diversity of neurophysiological processes underlying pain modulation through different psychological interventions.

Differential effects of visually induced analgesia and attention depending on the pain stimulation site

BACKGROUND

The term 'visually induced analgesia' describes a reduced pain perception induced by watching the painful body part as opposed to watching a neutral object. In chronic back pain patients, experimental pain, movement-induced pain and habitual pain can be reduced with visual feedback. Visual feedback can also enhance the effects of both massage treatment and manual therapy. The impact of somatosensory attentional processes remains unclear.

METHODS

In the current study, participants received painful electrical stimuli to their thumb and back while being presented with either a real-time video of their thumb or back (factor feedback). In addition, using an oddball paradigm, they had to count the number of deviant stimuli, applied to either their back or thumb (factor attention) and rate the pain intensity.

RESULTS

We found a significant main effect for attention with decreased pain ratings during attention. There was no main effect for visual feedback and no significant interaction between visual feedback and attention. Post-hoc tests revealed that the lowest pain intensity ratings were achieved during visual feedback of the back/ thumb and counting at the back/ thumb.

CONCLUSION

These data suggest that the modulation of perceived acute pain by visually induced analgesia may be influenced by a simultaneous somatosensory attention task.

SIGNIFICANCE

Somatosensory attention reduced experimental pain intensity in the thumb and back in the presence of both congruent and incongruent visual feedback. We found no significant visual feedback effect on the complex interplay between visual feedback and somatosensory attention.

Executive Functions and Pain

Abstract. A growing body of literature suggests that chronic-pain patients suffer from problems in various neuropsychological domains, including executive functioning. In order to better understand which components of executive functioning (inhibition, shifting and/or updating) might be especially affected by pain and which mechanisms might underlie this association, we conducted a systematic review, including both chronic-pain studies as well as experimental-pain studies. The chronic-pain studies (N = 57) show that pain is associated with poorer executive functioning. The findings of experimental-pain studies (N = 28) suggest that this might be a bidirectional relationship: Pain can disrupt executive functioning, but poorer executive functioning might also be a risk factor for higher vulnerability to pain.

Pain and Distraction According to Sensory Modalities: Current Findings and Future Directions

BACKGROUND

This review discusses the findings in the literature on pain and distraction tasks according to their sensory modality. Distraction tasks have been shown to reduce (experimentally induced) acute pain and chronic pain. This can be influenced by nature and by the sensory modalities used in the distraction tasks. Yet the effect on reducing pain according to the sensory modality of the distraction task has received little attention.

METHODS

A bibliographic search was performed in different databases. The studies will be systematized according to the sensory modality in which the distraction task was applied.

RESULTS

The analyzed studies with auditory distractors showed a reduction of acute pain in adults. However, these are not effective at healthy children and in adults with chronic pain. Visual distractors showed promising results in acute pain in adults and children. Similarly, tactile and mixed distractors decreased acute pain in adults.

CONCLUSION

Distraction tasks by diverse sensory modalities have a positive effect on decreasing the perception of acute pain in adults. Future studies are necessary given the paucity of research on this topic, particularly with tactile distractors (there is only one study). Finally, the most rigorous methodology and the use of ecological contexts are encouraged in future research.

Comparing the effects of sustained and transient spatial attention on the orienting towards and the processing of electrical nociceptive stimuli

We examined whether sustained vs. transient spatial attention differentially affect the processing of electrical nociceptive stimuli. Cued nociceptive stimuli of a relevant intensity (low or high) on the left or right forearm required a foot pedal press. The cued side varied trial wise in the transient attention condition, while it remained constant during a series of trials in the sustained attention condition. The orienting phase preceding the nociceptive stimuli was examined by focusing on lateralized EEG activity. ERPs were computed to examine the influence of spatial attention on the processing of the nociceptive stimuli. Results for the orienting phase showed increased ipsilateral alpha and beta power above somatosensory areas in both the transient and the sustained attention conditions, which may reflect inhibition of ipsilateral and/or disinhibition of contralateral somatosensory areas. Cued nociceptive stimuli evoked a larger N130 than uncued stimuli, both in the transient and the sustained attention conditions. Support for increased efficiency of spatial attention in the sustained attention condition was obtained for the N180 and the P540 component. We concluded that spatial attention is more efficient in the case of sustained than in the case of transient spatial attention.

Neural mechanisms underlying pain's ability to reorient attention: evidence for sensitization of somatic threat detectors

Pain typically signals damage to the body, and as such can be perceived as threatening and can elicit a strong emotional response. This ecological significance undoubtedly underlies pain's well-known ability to demand attention. However, the neural mechanisms underlying this ability are poorly understood. Previous work from the author's laboratory has reported behavioral evidence suggesting that participants disengage their attention from an incorrectly cued visual target stimulus and reorient it toward a somatic target more rapidly when the somatic target is painful than when it is nonpainful. Furthermore, electrophysiological data suggest that this effect is mediated by a stimulus-driven process, in which somatic threat detectors located in the dorsal posterior insula activate the medial and lateral prefrontal cortex areas involved in reorienting attention toward the painful target. In these previous studies, the painful and nonpainful somatic targets were given in separate experiments involving different participants. Here, the nonpainful and painful somatic targets were presented in random order within the same block of trials. Unlike in the previous studies, both the nonpainful and painful somatic targets activated the somatic threat detectors, and the times taken to disengage and reorient attention were the same for both. These electrophysiological and behavioral data suggest that somatic threat detectors can become sensitized to nonpainful somatic stimuli that are presented in a context that includes painful stimuli.

Neural underpinnings of behavioural strategies that prioritize either cognitive task performance or pain

We previously discovered that when faced with a challenging cognitive task in the context of pain, some people prioritize task performance, while in others, pain results in poorer performance. These behaviours, designated respectively as A- and P-types (for attention dominates vs pain dominates), may reflect pain coping strategies, resilience or vulnerabilities to develop chronic pain, or predict the efficacy of treatments such as cognitive behavioural therapy. Here, we used a cognitive interference task and pain stimulation in 80 subjects to interrogate psychophysical, psychological, brain structure and function that distinguish these behavioural strategies. During concurrent pain, the A group exhibited faster task reaction times (RTs) compared to nonpain trials, whereas the P group had slower RTs during pain compared to nonpain trials, with the A group being 143 ms faster than the P group. Brain imaging revealed structural and functional brain features that characterized these behavioural strategies. Compared to the performance-oriented A group, the P group had (1) more gray matter in regions implicated in pain and salience (anterior insula, anterior midcingulate cortex, supplementary motor area, orbitofrontal cortex, thalamus, caudate), (2) greater functional connectivity in sensorimotor and salience resting-state networks, (3) less white matter integrity in the internal and external capsule, anterior thalamic radiation and corticospinal tract, but (4) were indistinguishable based on sex, pain sensitivity, neuroticism, and pain catastrophizing. These data may represent neural underpinnings of how task performance vs pain is prioritized and provide a framework for developing personalized pain therapy approaches that are based on behaviour-structure-function organization.

Distraction Reduces Both Early and Late Electrocutaneous Stimulus Evoked Potentials

Previous electroencephalography studies revealed mixed effects of sustained distraction on early negative and later positive event-related potential components evoked by electrocutaneous stimuli. In our study we further examined the influence of sustained distraction to clarify these discrepancies. Electrocutaneous stimuli of three intensities were delivered in pulse trains to the forearm either while participants attended the stimuli or while they performed a mental-arithmetic or a word-association distraction task. The amplitudes of the N1 and the late P2/P3a components were attenuated during both distraction tasks. These results seem to resolve the debate concerning the attentional modulation of the N1 component. Furthermore, we observed that the amplitude of the late P2/P3a component was strongly affected by stimulus change, in line with the opinion that this component is actually a P3a orienting response. Our study additionally revealed that habituation effects were reflected in lower intensity ratings and reduced amplitudes of the N1 and P3a components. The latter effects were independent of the type of task, which suggests that habituation is unaffected by attention.

The influence of transient spatial attention on the processing of intracutaneous electrical stimuli examined with ERPs

OBJECTIVE

Determine the influence of transient spatial attention on the processing of intracutaneous electrical stimuli.

METHODS

Electrical stimuli, a single pulse or five pulses, were presented at the index fingers of the left or right hand. The to-be-attended hand and stimulated finger varied randomly from trial to trial. Participants had to press a foot pedal only when the relevant stimulus, varied between participants, occurred at the attended hand. EEG was measured to extract relevant ERP components.

RESULTS

The N100 and N150 were enhanced for attended as compared to unattended stimuli. The N100, N150, P260, and the P500 were enlarged for five pulse as compared to single pulse stimuli. The P260, which is thought to reflect a call for attention, was enhanced for unattended as compared to attended stimuli. Source analyses indicate that attentional effects on the N100, N150, and P260 may be related to changes in activity in secondary somatosensory areas and the anterior cingulate cortex.

CONCLUSIONS

A transient manipulation of spatial attention increases cortical activity induced by attended relative to unattended intracutaneous electrical stimuli, but initially unattended stimuli appear to induce an enhanced orienting effect.

SIGNIFICANCE

Initially unattended intracutaneous electrical stimuli seem to induce a call for attention.

Meditation experience predicts less negative appraisal of pain: electrophysiological evidence for the involvement of anticipatory neural responses

The aim of mindfulness meditation is to develop present-focused, non-judgmental, attention. Therefore, experience in meditation should be associated with less anticipation and negative appraisal of pain. In this study we compared a group of individuals with meditation experience to a control group to test whether any differences in the affective appraisal of pain could be explained by lower anticipatory neural processing. Anticipatory and pain-evoked ERPs and reported pain unpleasantness were recorded in response to laser stimuli of matched subjective intensity between the two groups. ERP data were analysed after source estimation with LORETA. No group effects were found on the laser energies used to induce pain. More experienced meditators perceived the pain as less unpleasant relative to controls, with meditation experience correlating inversely with unpleasantness ratings. ERP source data for anticipation showed that in meditators, lower activity in midcingulate cortex relative to controls was related to the lower unpleasantness ratings, and was predicted by lifetime meditation experience. Meditators also reversed the normal positive correlation between medial prefrontal cortical activity and pain unpleasantness during anticipation. Meditation was also associated with lower activity in S2 and insula during the pain-evoked response, although the experiment could not disambiguate this activity from the preceding anticipation response. Our data is consistent with the hypothesis that meditation reduces the anticipation and negative appraisal of pain, but effects on pain-evoked activity are less clear and may originate from preceding anticipatory activity. Further work is required to directly test the causal relationship between meditation, pain anticipation, and pain experience.

Performance-dependent inhibition of pain by an executive working memory task

It is widely assumed that distraction reduces pain. Similarly, it is assumed that pain distracts from concurrent, unrelated cognitive processing, reducing performance on difficult tasks. Taken together, these assumptions suggest pain processing and cognitive function engage an overlapping set of domain-general, capacity-limited mental resources. However, experimental tests of this proposal have yielded mixed results, leading to alternative proposals that challenge the common model of a bidirectional relationship between concurrent pain and task performance. We tested these contrasting positions using a novel concurrent pain and executive working memory paradigm. Both task difficulty and nociceptive stimulus intensity were individually calibrated for each participant. Participants reported less pain during the working memory task than a visually matched control condition. Conversely, increasing levels of heat incrementally reduced task performance. Path analyses showed that variations in pain completely mediated this effect, and that even within a given heat level, trial-by-trial fluctuations in pain predicted decrements in performance. In sum, these findings argue that overlapping cognitive resources play a role in both pain processing and executive working memory. Future studies could use this paradigm to understand more precisely which components of executive function or other cognitive resources contribute to the experience of pain.

Neural mechanisms of detecting and orienting attention toward unattended threatening somatosensory target stimuli. II. Intensity effects

Negative potentials evoked by painful electrical stimulation of the sural nerve that occur at 100-180 ms poststimulus over the contralateral temporal scalp (CTN100-180) and at 130-200 ms over the fronto-central scalp (FCN130-200) exhibit unusual attention effects. That is, their amplitudes are larger when the painful evoking stimulus is unattended than when it is attended. In this experiment, I show that attention has no effect on the CTN100-180 evoked by a weak, nonthreatening sural nerve electrical stimulus. These data suggest that the generators of the CTN100-180, which include the somatosensory association areas in the parietal operculum, are specifically involved in detecting threatening somatosensory stimuli. The FCN130-200 showed a small increase in the unattended condition, which is consistent with the role of its medial prefrontal cortex generators in monitoring any situation that might require a change in attentional control.

Neural mechanisms of detecting and orienting attention toward unattended threatening somatosensory targets. I. Intermodal effects

Our previous work has identified four components of the somatosensory-evoked potential elicited by painful electrical stimulation of the sural nerve that might index an involuntary process that detects and orients attention toward threatening somatosensory stimuli. These components include a negativity over the central scalp at 70-110 ms poststimulus (CN70-110), a contralateral temporal negativity at 100-180 ms (CTN100-180), a frontocentral negativity at 130-200 ms, and a positive potential at 270-340 ms (the pain-related P2). The results of the endogenous cuing experiment used here suggest that the CN70-110 and CTN100-180 index somatosensory cortex activity that detects a threatening somatosensory stimulus when the subject's attention is focused on another stimulus modality but not another location. The P2, on the other hand, appears to index inferior parietal cortex activity that is specifically involved in orienting spatial attention.

Influence and stability of pain scale anchors for an investigation of cold pressor pain tolerance

Variable use of pain scale anchors may influence recalled pain ratings, rating consistency, and agreement between actual rating change and ratings of pain relief. This investigation examined change in events that represent maximal pain scale anchors. Participants (N = 68, 50% women) provided events for maximal anchors of 0 to 100 pain scales, and cold pressor pain was rated by using self-selected event/s and an investigator-provided event. Participants then were allowed to change their self-selected event/s. The revised event/s or original events were then used to rate a second cold pressor trial. Forty-one percent of participants changed event/s, and the new event/s was more likely to involve cold or heat, but the painfulness of events and the pain ratings of the second trial did not change. The cold pressor pain ratings were higher when rated on the basis of self-selected event/s than the investigator-provided event for intensity (mean = 80.13, SD = 19.30; mean = 60.81, SD = 27.45) and unpleasantness (mean = 80.84, SD = 19.07; mean = 59.07, SD = 27.53), which could be due to the submaximal painfulness of the investigator-provided event. Therefore, the width of numerical scales is stable with maximal events regardless of the actual events.

PERSPECTIVE

This report identifies change in physical events that are used by participants to represent maximal pain scale anchors and suggests that the maximal nature of the events' painfulness is more important than variability in the actual events. We conclude that the numerical pain scales we used are understandable and stable, but we suggest that instructional sets for pain measurement may be improved by evaluation of the painfulness of events that respondents use to conceptualize maximal pain scale anchors.

Psychological risk factors in headache

Headache is a chronic disease that occurs with varying frequency and results in varying levels of disability. To date, the majority of research and clinical focus has been on the role of biological factors in headache and headache-related disability. However, reliance on a purely biomedical model of headache does not account for all aspects of headache and associated disability. Using a biopsychosocial framework, the current manuscript expands the view of what factors influence headache by considering the role psychological (i.e., cognitive and affective) factors have in the development, course, and consequences of headache. The manuscript initially reviews evidence showing that neural circuits responsible for cognitive-affective phenomena are highly interconnected with the circuitry responsible for headache pain. The manuscript then reviews the influence cognitions (locus of control and self-efficacy) and negative affect (depression, anxiety, and anger) have on the development of headache attacks, perception of headache pain, adherence to prescribed treatment, headache treatment outcome, and headache-related disability. The manuscript concludes with a discussion of the clinical implications of considering psychological factors when treating headache.

Human intracranially-recorded cortical responses evoked by painful electrical stimulation of the sural nerve

Intracranial recordings were obtained from 5 epilepsy patients to help identify the generators of the scalp somatosensory evoked potential (SEP) components that appear to be involved in orienting attention towards a potentially threatening, painful sural nerve electrical stimulus. The intracranial recording data support, for the most part, the generators suggested by our scalp SEP studies. The generators of the central negativity at 70-110 ms post-stimulus and the contralateral temporal negativity at 100-180 ms are located in the somatosensory association areas in the medial wall of the parietal cortex and in the parietal operculum and insula, respectively. The negative potential at 130-200 ms recorded from over the fronto-central scalp appears to be generated in the medial prefrontal cortex and primary somatosensory cortex foot area. The intracranial recording data suggest that the positive scalp potential at 280-320 ms, which corresponds to the pain-related P2, has multiple generators, including the anterior cingulate cortex, inferior parietal cortex, and possibly the somatosensory association areas in the medial wall of the parietal cortex. Finally, the positive scalp potential at 320-400 ms has generators in brain areas that others have shown to generate the P3a, including the dorsolateral and medial prefrontal cortices, temporal parietal junction, and the posterior hippocampus, which supports our hypothesis that this potential is a pain-evoked P3a. The putative functional roles of the brain areas generating these components and the response properties of the intracranial peaks recorded from these brain areas are in most cases consistent with the attention- and pain-related properties of their corresponding scalp SEP components. The intracranial recordings also demonstrate that the source configuration underlying the SEP components are often more complex than was suggested from the scalp studies. This complexity implies that the dipole source localization analysis of these components will at best provide only a very crude estimate of source location and activity, and that caution must be used when interpreting a change in the scalp component amplitude.