The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial
Timing and gender determine if acute pain impairs working memory performance.
The effects of pain on memory are complex, and little is known about the vulnerability of working memory (WM) performance when individuals complete a WM test while concurrently experiencing pain. Here, we subjected 78 healthy nonsmoking participants to either acute pain or a control condition while we administered a WM test. In this context, we also tested WM 20 minutes after pain in order to determine if timing of pain affected WM performance, and assessed objective and subjective measures of pain. We hypothesized that pain would impair WM performance during pain. Further, women's WM performance would be impaired more than men. Importantly, there was an interaction between gender and condition, with women exposed to pain experiencing impairments during but not after the cold pressor task. Our data imply that timing and gender are critically important in whether acute pain is costly to WM performance. Our findings have interesting clinical, professional, and educational implications, and understanding the influence of pain could help to improve the interpretation of WM tests in these diverse settings. ⋯ Results of this study support the growing body of work that attests to the detrimental effect of pain on WM performance. Further, this study provides new evidence that concurrently experiencing cold pressor pain impairs WM in regularly menstruating women and women taking a contraceptive.
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Despite the high prevalence of neck pain among women, menstrual effects on regional pain outcomes have not been investigated in this clinical population. This study evaluated menstrual effects on mechanical pain sensitivity (pressure pain threshold [PPT]), neck pain intensity (numeric pain rating scale [NPRS]), and neck-related disability (Neck Disability Index [NDI]) in 22 normally menstruating (NM) and 17 hormonal contraceptive users with chronic neck pain. Sex hormones, PPT, and NDI were measured during the early follicular (F1), late follicular (F2), and luteal (L) menstrual phases. Daily NPRS scores were recorded in an online symptom diary and averaged within each phase. Estradiol and progesterone increased only for NM women in F2 and L, respectively. Phase effects on PPT (η(2) = .003), NDI (η(2) = .003), and NPRS (η(2) = .016) for NM women were small and did not differ from those for the hormonal contraceptive users (P ≥ .386). Averaged across the menstrual cycle, PPT scores explained 29% of the variance in NPRS scores for NM women but were not associated with NDI scores in either group. Results indicate that the magnitude of menstrual effects on mechanical pain sensitivity and the severity of neck pain and disability do not exceed thresholds of clinically detectable change in women with chronic neck pain. ⋯ Fluctuations in evoked and clinical pain outcomes across the menstrual cycle do not appear to be of sufficient magnitude to impact clinical decision making for women with chronic neck pain.
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Vicarious pain has been shown to enhance observers' nociceptive reactivity and pain perception. We exposed healthy participants to specific parts of facial pain expressions in order to investigate which components are required to induce this modulation. We created 2 classes of stimuli: one containing the most useful information for identification of pain expressions (diagnostic) and one containing the least useful information (antidiagnostic). Twenty-eight normal volunteers received electrical stimulation of the sural nerve immediately after they viewed these stimuli. Subjective ratings (intensity and unpleasantness) as well as the nociceptive flexion reflex (NFR) evoked by the shock were recorded. Results show that diagnostic stimuli lead to higher subjective ratings of shock pain than the antidiagnostic stimuli, but the stimuli classes had no significant impact on the NFR. A control experiment showed that our facial stimuli were given very low valence and arousal ratings compared to stimuli previously used to demonstrate the effect of emotional pictures on pain. Thus, the results are unlikely to be explained by emotions felt by the observer and suggest a vicarious facilitation of supraspinal pain processing induced by key features underlying pain expressions recognition. Results provide further support to the perception-action model of empathy. ⋯ This study demonstrates that visual features that are efficiently used for the recognition of pain expressions are sufficient to induce a vicarious facilitation of self-pain. Supraspinal pain responses were modulated by the informativeness of the areas of the pain expressions that participants viewed prior to the painful stimulations.
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Somatic symptoms experienced by women with a menstrually related mood disorder (MRMD) during their premenstrual luteal phase contribute to functional impairment. Yet, investigations on pathophysiological mechanisms contributing to heightened pain sensitivity in MRMD are sparse. During the luteal phase, 61 women with an MRMD and 61 non-MRMD controls were evaluated for β-adrenergic receptor (β-AR) responsivity using the isoproterenol sensitivity test. A subset (43 MRMD and 50 non-MRMD) then entered a double-blind, placebo-controlled, crossover protocol to examine the effect of β-AR blockade with intravenous propranolol on sensitivity to experimental (cold pressor and ischemic) and clinical (McGill Pain Questionnaire score) pain. Women with an MRMD exhibited greater β1- and β2-AR responsivity, ischemic pain intensity, and affective clinical pain ratings than controls. Propranolol increased cold pressor pain tolerance in both groups, but it decreased cold pain intensity and ischemic pain unpleasantness ratings only in non-MRMD women. In contrast, propranolol decreased affective ratings of clinical pain in women with MRMD. Exploratory analyses indicated that only in MRMD women did greater β-AR responsivity predict greater sensitivity to cold pressor and ischemic pain. This study provides the first evidence for a role of β-AR mechanisms in the hyperalgesia and clinical pain experienced by women with MRMDs. ⋯ This article describes the effects of β-adrenergic receptor stimulation and blockade on experimental and clinical pain sensitivity in women with an MRMD. The results of this study may have implications for the management of the substantial somatic premenstrual symptomatology experienced by women with an MRMD.
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The dominant socioaffective model of empathy has emphasized the overlap between brain mechanisms involved in the encoding and the decoding of internal states. The role of dispositional empathy has been extensively studied in this research, but several other individual factors fundamental to communication processes have been largely ignored. We studied the effects of dispositional expressiveness in chronic back pain patients to determine if the decoding of communicative and noncommunicative information signaling pain in others would be enhanced in individuals displaying a spontaneous propensity to consistently express more pain during a behavioral-observational naturalistic standardized lifting task performed on 2 separate occasions. Blood oxygenation level-dependent signal change was measured in response to pictures showing facial pain expressions and hands/feet in pain-evoking situations in chronic back pain patients and healthy controls. Vicarious brain responses to others' pain were comparable between groups. However, more expressive patients rated others' pain higher and showed stronger vicarious pain responses in the right ventral part of the inferior frontal gyrus, the right insula, and the midbrain. Activity in the right insula correlated positively with both the patients' expressiveness (encoding) and the intensity of the pain perceived in the images (decoding), suggesting that this structure linked the dispositional expressiveness with vicarious pain perception. Importantly, these effects were independent from dispositional empathy and were found with both communicative (facial expression) and noncommunicative (hand and foot) cues. These results suggest that dispositional expressiveness is a self-related factor that facilitates vicarious pain processing and might reflect individual tendencies to rely on social coping strategies. ⋯ This article shows that pain expressivity in chronic pain patients increased the vicarious brain responses and the sensibility to others' pain. These results may help provide empirical support for better defining models of pain communication in chronic pain patients.