Amy E. Williams

Emotional control of nociceptive reactions (ECON): Do affective valence and arousal play a role?

&NA; Prior research suggests emotional picture‐viewing modulates motoric (nociceptive flexion reflex), autonomic (skin conductance response, heart rate acceleration), and subjective (pain rating) reactions to noxious electrodermal stimulation. The present study sought to determine whether emotional valence and arousal contribute to nociception modulation. To do so, pictures varying in emotional content (erotica, food, neutral, loss, attack) were chosen to manipulate emotional valence (pleasant = erotic and food; unpleasant = loss and attack) and arousal (low = food and loss; moderate = erotica and attack). Pictures were presented in pseudorandom order to elicit emotional processing while noxious electric stimulations were delivered to the sural nerve. Nociceptive flexion reflex (NFR) magnitude, skin conductance response (SCR), heart rate (HR) acceleration, and subjective pain ratings to each stimulation were measured, standardized, averaged by picture content, and analyzed. Results suggested that picture‐viewing explained 52% of the variance in the multivariate combination of the nociceptive reactions and modulated them in parallel. Pleasant pictures inhibited reactions, whereas unpleasant pictures enhanced them. However, only erotica and attack pictures elicited significant modulation relative to neutral pictures, suggesting arousal also contributed. An exploratory multilevel analysis also supported this conclusion. Together, these data suggest emotional control of nociceptive reactions (ECON) is associated with a valence‐by‐arousal interaction. Implications of these findings for how emotional picture‐viewing can be used to study supraspinal modulation are discussed.

Gender Differences in Pain: Do Emotions Play a Role?

BACKGROUND Research suggests that the influence of gender on the processing and experience of pain is a result of several mechanisms. One mediating variable is emotion, which may modulate pain through an interaction of valence (pleasant-unpleasant) and arousal (calm-excited). OBJECTIVE This review examines whether gender differences in the experience and processing of emotion contribute to differences in the modulation and perception of pain. METHODS An English-language search of MEDLINE and PsycINFO was conducted from 1887 to May 2005. Additional literature was obtained from reference lists of articles retained in the initial search. RESULTS Emotion appears to influence pain through a valence-by-arousal interaction. Specifically, negatively valenced emotions with low to moderate arousal (eg, anxiety) enhance pain, whereas negatively valenced emotions with high arousal (eg, fear) reduce pain. In contrast, positively valenced emotions always reduce pain, as long as minimal arousal is achieved. Some evidence suggests that women are more sensitive than men to threat-related stimuli and thus experience more negative affect than men. This would generally lead to enhanced pain perception in women. It is also possible that women are more likely than men to experience negative affect with high arousal (intense fear) and thus pain inhibition. However, the relatively lower base rate of intense negative emotions is not likely to contribute much to gender differences in pain. Evidence also suggests that men may be more sensitive to positive events, particularly sexual/erotic stimuli, which may lead to more positive emotion-induced pain reduction in men, relative to women. CONCLUSIONS This review suggests that gender differences in the experience of pain may arise from differences in the experience and processing of emotion that, in turn, differentially alter pain processing. Specifically, the system associated with negative affect may be more attuned to threatening stimuli in women, and the system associated with positive affect may be more attuned to pleasurable stimuli in men. However, there is a paucity of research directly addressing this issue; much of the research on this topic has failed to test a comprehensive model of emotion, failed to use adequate manipulation checks, or failed to use within-subject experimental designs that control for intra- and interindividual differences. Therefore, it is concluded that additional research is warranted.

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

&NA; 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.

Habituation, sensitization, and emotional valence modulation of pain responses

&NA; The Emotional Controls of Nociception (ECON) paradigm involves the presentation of emotionally‐charged pictures during which painful stimuli are delivered. Across several ECON studies, unpleasant pictures enhanced pain and nociception, whereas pleasant pictures inhibited pain and nociception. However, at this time it is unknown whether emotional valence (unpleasant, neutral, pleasant) influences the habituation or sensitization of pain responses that occurs within a testing session. Indeed, ECON assumes that emotional valence modulation of pain is consistent throughout testing; otherwise the interpretation of valence modulation (unpleasant > neutral > pleasant) could be threatened. To address this issue, the present study (N = 120) presented 108 pictures that varied in emotional valence. During and in between pictures, 52 suprathreshold electrocutaneous stimuli were delivered to evoke pain, the nociceptive flexion reflex [NFR], and pain‐evoked skin conductance response [SCR]. Mixed effects ANOVAs verified that within‐subject changes in pain responses were influenced by stimulus repetition (NFR and SCR habituated, pain ratings sensitized) and emotional valence (responses were highest during unpleasant pictures, intermediate during neutral pictures, and lowest during pleasant pictures). However, habituation/sensitization slopes were unaffected by emotional valence, thus indicating emotional valence modulation was consistently observed throughout the testing session. These results provide additional validation for the ECON paradigm and suggest that the circuit responsible for emotional modulation of pain and nociception is less susceptible to habituation or sensitization than the circuits responsible for responses to suprathreshold shocks.

Does Pain Catastrophizing Moderate the Relationship Between Spinal Nociceptive Processes and Pain Sensitivity

UNLABELLED Existing evidence indicates that pain catastrophizing is associated with enhanced pain reports and lower pain threshold/tolerance levels, but is not significantly related to nociceptive flexion reflex (NFR) threshold in healthy and clinical pain samples. This suggests pain catastrophizing may modulate pain threshold at a supraspinal level without influencing descending modulation of spinal nociceptive inputs. To examine this issue further, the present study assessed NFR threshold, electrocutaneous pain threshold, and electrocutaneous pain tolerance, as well as subjective ratings of noxious stimuli in a sample of 105 healthy adults. Pain catastrophizing was assessed prior to testing using traditional instructions and after pain testing with instructions to report on cognitions during testing (situation-specific catastrophizing). As expected, NFR threshold was correlated with pain sensitivity measures, but uncorrelated with both measures of catastrophizing. Although situation-specific catastrophizing was correlated with some pain outcomes, neither catastrophizing measure (traditional or situation specific) moderated the relationship between NFR and pain sensitivity. These findings confirm and extend existing evidence that catastrophizing influences pain reports through supraspinal mechanisms (eg, memory, report bias, attention) without altering transmission of spinal nociceptive signals. PERSPECTIVE Assessing catastrophic thoughts related to a specific painful event (situation-specific catastrophizing) provides important additional information regarding the negative cognitions that influence pain-related processes. However, neither situation-specific nor traditionally measured pain catastrophizing appear to enhance pain by engaging descending controls to influence spinal nociceptive processes.

Physiological predictors of response to exposure, relaxation, and rescripting therapy for chronic nightmares in a randomized clinical trial.

STUDY OBJECTIVES Evidence supports the use of cognitive behavioral therapies for nightmares in trauma-exposed individuals. This randomized clinical trial replicated a study of exposure, relaxation, and rescripting therapy(ERRT) and extended prior research by including broad measures of mental health difficulties, self-reported physical health problems, and quality of life. Additionally, physiological correlates of treatment-related change assessed from a script-driven imagery paradigm were examined. METHODS Forty-seven individuals were randomized to treatment or waitlist control. RESULTS The treatment group demonstrated improvements relative to the control group at the one-week post-treatment assessment. At the 6-month follow-up assessment, significant improvements were found for frequency and severity of nightmares, posttraumatic stress disorder symptoms, depression, sleep quality and quantity, physical health symptoms, anger, dissociation, and tension reduction behaviors. Participants also reported improved quality of life. Treatment-related decreases in heart rate to nightmare imagery were correlated with improvements in sleep quality and quantity; treatment-related decreases in skin conductance to nightmare imagery were correlated with improvements in nightmare severity, posttraumatic stress disorder symptom severity, sleep quality, and fear of sleep; and treatment-related decreases in corrugator activity to nightmare imagery were correlated with improved physical health. CONCLUSIONS Findings provide additional support for the use of ERRT in treating nightmares and related difficulties and improving sleep.

Cognitive-behavioral treatment for chronic nightmares in trauma-exposed persons: assessing physiological reactions to nightmare-related fear

Cognitive-behavioral treatments (CBTs) that target nightmares are efficacious for ameliorating self-reported sleep problems and psychological distress. However, it is important to determine whether these treatments influence objective markers of nightmare-related fear, because fear and concomitant physiological responses could promote nightmare chronicity and sleep disturbance. This randomized, controlled study (N=40) assessed physiological (skin conductance, heart rate, facial electromyogram) and subjective (displeasure, fear, anger, sadness, arousal) reactions to personally relevant nightmare imagery intended to evoke nightmare-related fear. Physiological assessments were conducted at pretreatment as well as 1-week, 3-months, and 6-months posttreatment. Results of mixed effects analysis of variance models suggested treatment reduced physiological and subjective reactions to nightmare imagery, gains that were generally maintained at the 6-month follow-up. Potential implications are discussed.

Psychophysiological responses to pain: Further validation of the nociceptive flexion reflex (NFR) as a measure of nociception using multilevel modeling

Physiological reactions to noxious stimuli are often used to make inferences about pain, but few studies have thoroughly examined the intra- and interindividual relationships between them. In the present study (N=104), multilevel analyses was used to assess relations between physiological (nociceptive flexion reflex magnitude [NFR], blink reflex magnitude, skin conductance response [SCR], heart rate [HR]) and subjective reactions to electrocutaneous stimuli. All physiological reactions were significant predictors of ratings when entered alone, explaining 1% (SCR) to 29% (NFR) of the variance; but only NFR, blink, and HR were significant in a multivariate predictor model. Significant interindividual variability in slopes was found for blink and HR, but not NFR. A final trimmed model that included NFR, blink, and the blink random slope explained 35% of the variance in ratings.

Experimental Assessment of Affective Processing in Fibromyalgia

UNLABELLED Fibromyalgia syndrome (FMS) is a chronic pain disorder associated with widespread musculoskeletal pain, tenderness, and fatigue. Additionally, correlational research suggests negative affect (eg, depression, anxiety) and deficits in positive affect may contribute to FMS symptomatology. However, well-controlled, experimental research is necessary to ascertain whether patients with FMS have problems in affective processing. The present study used a well-validated picture-viewing paradigm to evoke emotional responses in 17 patients with FMS and 17 sex- and age-matched healthy control participants. Each participant viewed pleasant (erotica), neutral, and unpleasant (attack related) pictures, and abrupt white noises were delivered during two-thirds of the pictures to evoke startle eyeblinks. Appetitive and defensive responding was assessed from subjective (valence/pleasure and arousal ratings) and physiological (corrugator EMG, heart rate, skin-conductance response, startle-reflex modulation) reactions to pictures. Results suggested FMS was associated with greater defensive activation (displeasure, subjective arousal, corrugator EMG) to the unpleasant, threat-related pictures, but not deficits in appetitive activation to erotic pictures. Although preliminary, these data suggest individuals with FMS have deficits in affective processing, but this dysregulation may be limited to defensive activation. Implications for treatment and future research are discussed. PERSPECTIVE Fibromyalgia is a debilitating disease associated with affective distress. Results from the present study suggest that FMS is associated with enhanced defensive activation to nonpainful threat-related stimuli, but not deficits in appetitive reactions to erotic stimuli. These findings have implications for the treatment and study of FMS.

Are There Sex Differences in Affective Modulation of Spinal Nociception and Pain

UNLABELLED Sex differences in the processing and experience of emotion exist. The present study examined whether sex differences in emotion lead to sex differences in affective modulation of pain and spinal nociception (assessed by nociceptive flexion reflex, NFR). Participants were healthy men (n = 47) and women (n = 73). Prior to affective modulation testing, electrocutaneous pain sensitivity was assessed (NFR threshold, pain threshold, pain tolerance). Affective modulation of pain and NFR was then assessed by presenting pictures that vary in emotional valence and arousal (mutilation, attack, death, neutral, families, adventure, erotica) during which suprathreshold electrocutaneous stimulations were delivered. Subjective emotional reactions were assessed after every picture, and nociceptive reactions were assessed after every suprathreshold stimulus. Results indicated women had greater pain sensitivity and also responded more negatively to attack pictures and less positively to erotic pictures. But despite these differences, affective modulation of pain/NFR was not moderated by sex: erotic pictures inhibited pain/NFR and mutilation pictures enhanced pain/NFR. Together, this implies subjective emotional experience does not completely mediate picture-evoked modulation of pain/NFR, a supposition that was further supported by exploratory analyses that demonstrated picture-evoked modulation of pain/NFR was present even after controlling for intra- and inter-individual differences in emotional reactions to pictures. Implications and limitations of these findings are discussed. PERSPECTIVE Evidence suggests that women are more sensitive to experimental and clinical pain, but the mechanisms contributing to these sex differences are poorly understood. Affective processes are known to play a role in regulating pain signaling and pain experience; therefore, the present study examined whether sex differences in affective experience contribute to sex differences in pain. Results indicate that in healthy individuals affective processes may not contribute to sex differences in pain.