Reduced heat pain thresholds after sad-mood induction are associated with changes in thalamic activity

The effect of experimental emotion induction on experimental pain: a systematic review and meta-analysis

ABSTRACT

The idea that emotions can influence pain is generally recognized. However, a synthesis of the numerous individual experimental studies on this subject is lacking. The aim of the present systematic review and meta-analysis was to synthesize the existing evidence on the effect of experimental emotion induction on experimental pain in nonclinical adults. PsycInfo and PubMed were searched up until April 10, 2023, for studies assessing differences in self-reported pain between emotion induction groups and/or control groups or between conditions within group. Risk of bias was assessed for the individual studies. The literature search yielded 78 relevant records of 71 independent studies. When compared with control conditions, the pooled results revealed a statistically significant pain-attenuating effect of positive emotion induction (between-group: Hedges g = -0.48, 95% CI: -0.72; -0.25, K = 9; within-group: g = -0.24, 95% CI: -0.32; -0.15, K = 40), and a statistically significant pain-exacerbating effect of negative emotion induction in within-group analyses but not between-group analyses (between-group: g = -0.29, 95% CI: -0.66; 0.07, K = 10; within-group: g = 0.14, 95% CI: 0.06; 0.23, K = 39). Bayesian meta-analysis provided strong support for an effect of positive emotion induction but weak support for an effect of negative emotion induction. Taken together, the findings indicate a pain-attenuating effect of positive emotion induction, while the findings for negative emotion induction are less clear. The findings are discussed with reference to theoretical work emphasizing the role of motivational systems and distraction for pain. Limitations include considerable heterogeneity across studies limiting the generalizability of the findings.

Frequency of Spinal Segmental Sensitization Syndrome and Associated Social Determinants of Health

OBJECTIVE

To determine the frequency of spinal segmental sensitization (SSS) syndrome and its association with socioeconomic and educational levels, Depression, smoking, and alcoholism.

DESIGN

Analytic cross-sectional study conducted within the time frame of February-August 2022.

SETTING

Outpatient consultation area of the Hospital Regional Universitario de Colima, a public health care institution in Mexico PARTICIPANTS: Ninety-eight patients over 18 years of age were selected that presented with chronic musculoskeletal pain of at least 3-month progression (N=98). The patients were initially selected through simple random sampling, complementing 60% of the calculated sample with consecutive cases due to the pandemic status.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE(S)

The subjects gave their informed consent, authorizing the clinical history interview and physical examination that applied the 2019 diagnostic criteria of Nakazato and Romero, as well as the AMAI test, the Mexican National Education System, the Beck Depression Inventory, Fagerstrom Test, and Alcohol Use Disorders Identification Test instrument, to collect the data on socioeconomic and educational levels, Depression, smoking, and alcoholism, respectively. Frequencies and percentages were obtained for the statistical analysis, using the chi-square test, multiple logistic regression, and bivariate/multivariate analyses with the prevalence odds ratio.

RESULTS

SSS had a 22.4% frequency and was significantly associated (P<.05) with moderate Depression and severe Depression, signifying that a patient with moderate depression had 5.57 times more probability of presenting with SSS (95% CI, 1.27-30.16, P<.05), whereas a patient with severe Depression had 8.68 times more probability of presenting with SSS (95% CI, 1.99-47.77, P<.05). The results of the remaining variables were not statistically significant.

CONCLUSIONS

There is a need for a biopsychosocial focus on SSS, in which the detection of and approach to moderate and severe Depression favors patient awareness of aspects associated with the phenomenon of chronic pain and the creation of coping strategies for that pain.

Pain sensitivity is modulated by affective temperament: Results from the population-based CHRIS Affective Disorder (CHRIS-AD) study

BACKGROUND

Nociceptive pain modulation is related to psychological and psychiatric conditions. Evidence from clinical studies backs innate temperaments as potential precursors of mood symptoms and disorders, and pain sensitivity. Our study examines the modulation effect of affective temperaments on pain sensitivity in a general population adult sample, accounting for possible intervening mood symptoms, lifetime anxiety and depression, and pain treatments.

METHODS

The sample is part of the CHRIS-AD study, Italy. Primary outcomes were the pain sensitivity questionnaire PSQ-total intensity score and the experimental pressure pain threshold (PPT). Affective temperaments were evaluated with the TEMPS-M. Lifetime depression, anxiety, current mood disorders, and treatments were self-reported via rating-scales. Directed acyclic graphs theory guided linear and mixed linear regression model analyses.

RESULTS

Among 3804 participants (aged 18-65; response rate 78.4 %, females 53.3 %, mean age 38.4 years) for any given temperament, both the PSQ-total and the PPT were associated with temperament. The TEMPS-M four cyclothymic-related temperaments aligned on the pain-sensitive pole and the hyperthymic on the pain-resilient pole. The inclusion of current or lifetime mood symptoms, or pain drug use, as possible intervening pathways only partly diluted these associations, with stronger evidence for an effect of trait anxiety.

LIMITATIONS

The main limitations were the lack of experimental measures of suprathreshold pain intensity perception, and detailed information on affective disorders in the study population.

CONCLUSIONS

These findings support the hypothesis of a biological dichotomous diathesis of affective temperaments towards pain sensitivity; hyperthymic suggesting protection, whereas cyclothymic suggesting predisposition.

Sound induces analgesia through corticothalamic circuits

Sound-including music and noise-can relieve pain in humans, but the underlying neural mechanisms remain unknown. We discovered that analgesic effects of sound depended on a low (5-decibel) signal-to-noise ratio (SNR) relative to ambient noise in mice. Viral tracing, microendoscopic calcium imaging, and multitetrode recordings in freely moving mice showed that low-SNR sounds inhibited glutamatergic inputs from the auditory cortex (ACx^Glu) to the thalamic posterior (PO) and ventral posterior (VP) nuclei. Optogenetic or chemogenetic inhibition of the ACx^Glu→PO and ACx^Glu→VP circuits mimicked the low-SNR sound-induced analgesia in inflamed hindpaws and forepaws, respectively. Artificial activation of these two circuits abolished the sound-induced analgesia. Our study reveals the corticothalamic circuits underlying sound-promoted analgesia by deciphering the role of the auditory system in pain processing.

Neural correlates of co-occurring pain and depression: an activation-likelihood estimation (ALE) meta-analysis and systematic review

The relationship between pain and depression is thought to be bidirectional and the underlying neurobiology 'shared' between the two conditions. However, these claims are often based on qualitative comparisons of brain regions implicated in pain or depression, while focused quantitative studies of the neurobiology of pain-depression comorbidity are lacking. Particularly, the direction of comorbidity, i.e., pain with depression vs. depression with pain, is rarely addressed. In this systematic review (PROSPERO registration CRD42020219876), we aimed to delineate brain correlates associated with primary pain with concomitant depression, primary depression with concurrent pain, and equal pain and depression comorbidity, using activation likelihood estimation (ALE) meta-analysis. Neuroimaging studies published in English until the 28th of September 2021 were evaluated using PRISMA guidelines. A total of 70 studies were included, of which 26 reported stereotactic coordinates and were analysed with ALE. All studies were assessed for quality by two authors, using the National Institute of Health Quality Assessment Tool. Our results revealed paucity of studies that directly investigated the neurobiology of pain-depression comorbidity. The ALE analysis indicated that pain with concomitant depression was associated with the right amygdala, while depression with concomitant pain was related primarily to the left dorsolateral prefrontal cortex (DLPFC). We provide evidence that pain and depression have a cumulative negative effect on a specific set of brain regions, distinct for primary diagnosis of depression vs. pain.

Brain Mechanisms of Pain and Dysautonomia in Diabetic Neuropathy: Connectivity Changes in Thalamus and Hypothalamus

CONTEXT

About one-third of diabetic patients suffer from neuropathic pain, which is poorly responsive to analgesic therapy and associated with greater autonomic dysfunction. Previous research on diabetic neuropathy mainly links pain and autonomic dysfunction to peripheral nerve degeneration resulting from systemic metabolic disturbances, but maladaptive plasticity in the central pain and autonomic systems following peripheral nerve injury has been relatively ignored.

OBJECTIVE

This study aimed to investigate how the brain is affected in painful diabetic neuropathy (PDN), in terms of altered structural connectivity (SC) of the thalamus and hypothalamus that are key regions modulating nociceptive and autonomic responses.

METHODS

We recruited 25 PDN and 13 painless (PLDN) diabetic neuropathy patients, and 27 healthy adults as controls. The SC of the thalamus and hypothalamus with limbic regions mediating nociceptive and autonomic responses was assessed using diffusion tractography.

RESULTS

The PDN patients had significantly lower thalamic and hypothalamic SC of the right amygdala compared with the PLDN and control groups. In addition, lower thalamic SC of the insula was associated with more severe peripheral nerve degeneration, and lower hypothalamic SC of the anterior cingulate cortex was associated with greater autonomic dysfunction manifested by decreased heart rate variability.

CONCLUSION

Our findings indicate that alterations in brain structural connectivity could be a form of maladaptive plasticity after peripheral nerve injury, and also demonstrate a pathophysiological association between disconnection of the limbic circuitry and pain and autonomic dysfunction in diabetes.

Functional consequences of acute tryptophan depletion on raphe nuclei connectivity and network organization in healthy women

Previous research on central nervous serotonin (5-HT) function provided evidence for a substantial involvement of 5-HT in the regulation of brain circuitries associated with cognitive and affective processing. The underlying neural networks comprise core subcortical/cortical regions such as amygdala and medial prefrontal cortex, which are assumed to be modulated amongst others by 5-HT. Beside the use of antidepressants, acute tryptophan depletion (ATD) is a widely accepted technique to manipulate of 5-HT synthesis and its respective metabolites in humans by means of a dietary and non-pharmacological tool. We used a double-blind, randomized, cross-over design with two experimental challenge conditions, i.e. ATD and tryptophan (TRP) supplementation (TRYP+) serving as a control. The aim was to perturb 5-HT synthesis and to detect its impact on brain functional connectivity (FC) of the upper serotonergic raphe nuclei, the amygdala and the ventromedial prefrontal cortex as well as on network organization using resting state fMRI. 30 healthy adult female participants (age: M ​= ​24.5 ​± ​4.4 ​yrs) were included in the final analysis. ATD resulted in a 90% decrease of TRP in the serum relative to baseline. Compared to TRYP ​+ ​for the ATD condition a significantly lower FC of the raphe nucleus to the frontopolar cortex was detected, as well as greater functional coupling between the right amygdala and the ventromedial prefrontal cortex. FC of the raphe nucleus correlated significantly with the magnitude of TRP changes for both challenge conditions (ATD & TRYP+). Network-based statistical analysis using time series from 260 independent anatomical ROIs revealed significantly greater FC after ATD compared to TRYP+ in several brain regions being part of the default-mode (DMN) and the executive-control networks (ECN), but also of salience or visual networks. Finally, we observed an impact of ATD on the rich-club organization in terms of decreased rich-club coefficients compared to TRYP+. In summary we could confirm previous findings that the putative decrease in brain 5-HT synthesis via ATD significantly alters FC of the raphe nuclei as well as of specific subcortical/cortical regions involved in affective, but also in cognitive processes. Moreover, an ATD-effect on the so-called rich-club organization of some nodes with the high degree was demonstrated. This may indicate effects of brain 5-HT on the integration of information flow from several brain networks.

At the intersection of alcohol use disorder and chronic pain

OBJECTIVE

Alcohol use disorder (AUD) and chronic pain are widespread conditions with extensive public health burden. This review seeks to describe neuroanatomical links and major mediating influences between AUD and chronic pain, in the service of identifying factors that predict the risk of chronic pain in precipitating or facilitating AUD.

METHOD

We review the neural bases of pain and the influence of AUD on processes involved in pain perception. We propose potential mechanisms involved in the development of chronic pain in AUD, and we consider implications for pain management in recovery from AUD.

RESULTS

Pain is a multidimensional and subjective experience that, in its acute form, is essential for survival, but in chronic form, pain is a disorder that negatively impacts quality of life. Neural substrates involved in initiating and maintaining chronic pain include dysfunction in descending pain pathways and reward network circuitry. AUD involves preoccupation or craving, intoxication, withdrawal, and negative affect. Neural substrates of AUD involve widespread mesocorticolimbic and cerebrocerebellar networks. Both conditions involve dysfunction of extended reward and oversight circuitry, particularly prefrontal cortex.

CONCLUSIONS

The interrelationship between chronic pain and AUD resides in the intersection of etiological influences, mental experiences, and neurobiological processes. Characterization of the connection between brain and behavioral abnormalities in AUD's precipitation of chronic pain-and vice versa-allows for early detection and treatment of patients at risk for developing either or both of these conditions and for preemptive interventional approaches to reduce the risk of consequent vulnerabilities and harm. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Phenotypic Features of Central Sensitization

PURPOSE

The current manuscript reviews approaches for phenotyping central sensitization (CS).

METHODS

The manuscript covers the concept of diagnostic phenotyping, use of endophenotypes, biomarkers, and symptom clusters. Specifically, the components of CS that include general sensory sensitivity (assessed by quantitative sensory testing) and a symptom cluster denoting sleep difficulties, pain, affect, cognitive difficulties, and low energy (S.P.A.C.E.).

RESULTS

Each of the assessment domains are described with reference to CS and their presence in chronic overlapping pain conditions (COPCs) - conditions likely influenced by CS.

CONCLUSIONS

COPCs likely represent clinical diagnostic phenotypes of CS. Components of CS can also be assessed using QST or self-report instruments designed to assess single elements of CS or more general composite indices.

"Luteal Analgesia": Progesterone Dissociates Pain Intensity and Unpleasantness by Influencing Emotion Regulation Networks

Background: Pregnancy-induced analgesia is known to occur in association with the very high levels of estradiol and progesterone circulating during pregnancy. In women with natural ovulatory menstrual cycles, more modest rises in these hormones occur on a monthly basis. We therefore hypothesized that the high estradiol high progesterone state indicative of ovulation would be associated with a reduction in the pain experience. Methods: We used fMRI and a noxious thermal stimulus to explore the relationship between sex steroid hormones and the pain experience. Specifically, we assessed the relationship with stimulus-related activity in key regions of networks involved in emotion regulation, and functional connectivity between these regions. Results: We demonstrate that physiologically high progesterone levels are associated with a reduction in the affective component of the pain experience and a dissociation between pain intensity and unpleasantness. This dissociation is related to decreased functional connectivity between the inferior frontal gyrus and amygdala. Moreover, we have shown that in the pre-ovulatory state, the traditionally "male" sex hormone, testosterone, is the strongest hormonal regulator of pain-related activity and connectivity within the emotional regulation network. However, following ovulation the traditionally "female" sex hormones, estradiol and progesterone, appear to dominate. Conclusions: We propose that a phenomenon of "luteal analgesia" exists with potential reproductive advantages.

Negative mood influences default mode network functional connectivity in patients with chronic low back pain: implications for functional neuroimaging biomarkers

The default mode network (DMN) has been proposed as a biomarker for several chronic pain conditions. Default mode network functional connectivity (FC) is typically examined during resting-state functional neuroimaging, in which participants are instructed to let thoughts wander. However, factors at the time of data collection (eg, negative mood) that might systematically impact pain perception and its brain activity, influencing the application of the DMN as a pain biomarker, are rarely reported. This study measured whether positive and negative moods altered DMN FC patterns in patients with chronic low back pain (CLBP), specifically focusing on negative mood because of its clinical relevance. Thirty-three participants (CLBP = 17) underwent resting-state functional magnetic resonance imaging scanning before and after sad and happy mood inductions, and rated levels of mood and pain intensity at the time of scanning. Two-way repeated-measures analysis of variances were conducted on resting-state functional connectivity data. Significant group (CLBP > healthy controls) × condition (sadness > baseline) interaction effects were identified in clusters spanning parietal operculum/postcentral gyrus, insular cortices, anterior cingulate cortex, frontal pole, and a portion of the cerebellum (PFDR < 0.05). However, only 1 significant cluster covering a portion of the cerebellum was identified examining a two-way repeated-measures analysis of variance for happiness > baseline (PFDR < 0.05). Overall, these findings suggest that DMN FC is affected by negative mood in individuals with and without CLBP. It is possible that DMN FC seen in patients with chronic pain is related to an affective dimension of pain, which is important to consider in future neuroimaging biomarker development and implementation.

Central Pain Processing in Early-Stage Parkinson's Disease: A Laser Pain fMRI Study

Background & Objective

Pain is a common non-motor symptom in Parkinson’s disease. As dopaminergic dysfunction is suggested to affect intrinsic nociceptive processing, this study was designed to characterize laser-induced pain processing in early-stage Parkinson’s disease patients in the dopaminergic OFF state, using a multimodal experimental approach at behavioral, autonomic, imaging levels.

Methods

13 right-handed early-stage Parkinson’s disease patients without cognitive or sensory impairment were investigated OFF medication, along with 13 age-matched healthy control subjects. Measurements included warmth perception thresholds, heat pain thresholds, and central pain processing with event-related functional magnetic resonance imaging (erfMRI) during laser-induced pain stimulation at lower (E = 440 mJ) and higher (E = 640 mJ) target energies. Additionally, electrodermal activity was characterized during delivery of 60 randomized pain stimuli ranging from 440 mJ to 640 mJ, along with evaluation of subjective pain ratings on a visual analogue scale.

Results

No significant differences in warmth perception thresholds, heat pain thresholds, electrodermal activity and subjective pain ratings were found between Parkinson’s disease patients and controls, and erfMRI revealed a generally comparable activation pattern induced by laser-pain stimuli in brain areas belonging to the central pain matrix. However, relatively reduced deactivation was found in Parkinson’s disease patients in posterior regions of the default mode network, notably the precuneus and the posterior cingulate cortex.

Conclusion

Our data during pain processing extend previous findings suggesting default mode network dysfunction in Parkinson’s disease. On the other hand, they argue against a genuine pain-specific processing abnormality in early-stage Parkinson’s disease. Future studies are now required using similar multimodal experimental designs to examine pain processing in more advanced stages of Parkinson’s disease.

A System Computational Model of Implicit Emotional Learning

Nowadays, the experimental study of emotional learning is commonly based on classical conditioning paradigms and models, which have been thoroughly investigated in the last century. Unluckily, models based on classical conditioning are unable to explain or predict important psychophysiological phenomena, such as the failure of the extinction of emotional responses in certain circumstances (for instance, those observed in evaluative conditioning, in post-traumatic stress disorders and in panic attacks). In this manuscript, starting from the experimental results available from the literature, a computational model of implicit emotional learning based both on prediction errors computation and on statistical inference is developed. The model quantitatively predicts (a) the occurrence of evaluative conditioning, (b) the dynamics and the resistance-to-extinction of the traumatic emotional responses, (c) the mathematical relation between classical conditioning and unconditioned stimulus revaluation. Moreover, we discuss how the derived computational model can lead to the development of new animal models for resistant-to-extinction emotional reactions and novel methodologies of emotions modulation.

Pain, quality of life and activity in aged evacuees living in temporary housing after the Great East Japan earthquake of 11 March 2011: a cross-sectional study in Minamisoma City, Fukushima prefecture

BACKGROUND

The aim of this study was to clarify pain, quality of life and activity in the aged evacuees living in temporary housing after the Great East Japan Earthquake on 11 March 2011.

METHODS

The study was a cross-sectional study performed in Minamisoma City, Fukushima Prefecture 1 year and 6 months after the disaster. Inclusion criteria were the ability to walk independently and consent to answer questionnaires. Seventy-one evacuees who met the inclusion criteria were included in this study. There were 16 men and 55 women with a mean age of 75.9 years. Sixty evacuees were surveyed when they gathered at the assembly hall in the temporary housing (Assembled group) and 11 evacuees were surveyed through individual visits to their residences (Individual group). Evacuees in the Individual group agreed to participate in this study, but refused to visit the assembly hall to engage in exercise and recreation. Pain, quality of life (QOL) and level of activity were assessed with the Numeric Rating Scale (NRS), the MOS Short-Form 36 item Health Survey (SF-36) and a pedometer, respectively. Student's t-test, Mann-Whitney U test, and Fisher's exact test were used for statistical analysis.

RESULTS

Forty-four (62.0 %) residents had chronic pain with a mean NRS of 2.74. Twenty-one (29.6 %) of these residents had relatively severe pain rated 5 or above on the NRS. QOL was significantly lower for the subscales of "physical functioning," "role physical", "general health", "social functioning", "role emotional" and "mental health", when compared with the national standard values. Values were also visibly lower for "physical component summary" in the summary score. On comparing the Assembled group and the Individual group, "physical function", "role physical", "social functioning" and "physical component summary" were found to be significantly lower in the Individual group. The mean daily number of steps was 1,892 in the Individual group and 4,579 in the Assembled group. The Individual group thus significantly took less mean daily number of steps compared with the Assembled group.

CONCLUSIONS

This study quantified the state of pain, QOL and activity of aged evacuees living in temporary housing after the Great East Japan Earthquake. The evacuees frequently had chronic pain and lower physical and mental QOL scores compared to the national standard values.

The neural basis of the abnormal self-referential processing and its impact on cognitive control in depressed patients

Persistent pondering over negative self-related thoughts is a central feature of depressive psychopathology. In this study, we sought to investigate the neural correlates of abnormal negative self-referential processing (SRP) in patients with Major Depressive Disorder and its impact on subsequent cognitive control-related neuronal activation. We hypothesized aberrant activation dynamics during the period of negative and neutral SRP in the rostral anterior cingulate cortex (rACC) and in the amygdala in patients with major depressive disorder. Additionally, we assumed abnormal activation in the fronto-cingulate network during Stroop task execution. 19 depressed patients and 20 healthy controls participated in the study. Using an event-related functional magnetic resonance imaging (fMRI) design, negative, positive and neutral self-referential statements were displayed for 6.5 s and followed by incongruent or congruent Stroop conditions. The data were analyzed with SPM8. In contrast to controls, patients exhibited no significant valence-dependent rACC activation differences during SRP. A novel finding was the significant activation of the amygdala and the reward-processing network during presentation of neutral self-referential stimuli relative to baseline and to affective stimuli in patients. The fMRI analysis of the Stroop task revealed a reduced BOLD activation in the right fronto-parietal network of patients in the incongruent condition after negative SRP only. Thus, the inflexible activation in the rACC may correspond to the inability of depressed patients to shift their attention away from negative self-related stimuli. The accompanying negative affect and task-irrelevant emotional processing may compete for neuronal resources with cognitive control processes and lead thereby to deficient cognitive performance associated with decreased fronto-parietal activation.

The importance of psychological assessment in chronic pain

PURPOSE OF REVIEW

Much confusion has surrounded the purpose of the psychological assessment in the context of chronic pain. For many clinicians, the psychological assessment is used to rule out psychiatric illness and to identify the nonmedical causes for pain and disability. In essence, it is used to identify the causes of pain that fall outside of the biomedical model. Supported by over 30 years of evidence, the bio-psycho-social model acknowledges that psychosocial factors are inherent in chronic pain and require assessment if meaningful diagnostics and treatments are to occur.

RECENT FINDINGS

Five broad categories of psychosocial assessment are relevant to chronic pain. These categories have been shown to enhance the diagnosis of the underlying forms of pain, predict the transition from acute to chronic status, and help to phenotype individuals for the discovery of the underlying mechanisms responsible for pain.

SUMMARY

Informed assessment of chronic pain needs to include relevant biological, psychological, and social domains. This article describes those domains and offers suggestions of specific instruments to use in clinical or research settings.

Further evidence of emotional allodynia in unmedicated young adults with major depressive disorder

BACKGROUND

Recent evidence suggests that sensitivity to the emotional sequela of experimental thermal pain(measured by emotional unpleasantness) is heightened in individuals with major depressive disorder(MDD), a phenomenon we termed "emotional allodynia". The aim of this study was to examine whether acute happy and sad mood induction alters emotional allodynia in MDD. We hypothesized that emotional allodynia will be a robust characteristic of individuals with MDD compared to healthy controls. Thus, it would remain following acute mood induction, independent of valence.

METHODS

Twenty-one subjects with current MDD and 21 well-matched healthy subjects(HC) received graded brief temperature stimuli following happy and sad mood inductions procedures(MIP). All subjects rated the intensity and affect(pleasantness/unpleasantness) of each stimulus. Sensory(pain intensity) and affective(pain unpleasantness) thresholds were determined by methods of constant stimuli.

RESULTS

The MIPs reliably induced happy and sad mood and the resulting induced mood and subjective arousal were not different between the groups at the time of temperature stimulation. Compared to HC, MDD individuals demonstrated emotional allodynia. We found significantly decreased affective pain thresholds whereby significantly lower temperatures became unpleasant in the MDD compared to the HC group. This was not observed for the sensory pain thresholds. Within the MDD, the affective pain thresholds were significantly lower than the corresponding pain intensity thresholds, whereby non-painful temperatures were already unpleasant for the MDD irrespective of the induced mood. This was not observed for the HC groups where the affective and pain intensity thresholds were comparable.

CONCLUSIONS

These findings suggest that emotional allodynia may be a chronic characteristic of current MDD. Future studies should determine if emotional allodynia persists after psychological or pharmacological interventions. Finally, longitudinal work should examine whether emotional allodynia is a result of or vulnerability for depression and the role it plays in the increased susceptibility for pain complaints in this disorder.

Self-referential processing influences functional activation during cognitive control: an fMRI study

Rostral anterior cingulate cortex (rACC) plays a central role in the pathophysiology of major depressive disorder (MDD). As we reported in our previous study (Wagner et al., 2006), patients with MDD were characterized by an inability to deactivate this region during cognitive processing leading to a compensatory prefrontal hyperactivation. This hyperactivation in rACC may be related to a deficient inhibitory control of negative self-referential processes, which in turn may interfere with cognitive control task execution and the underlying fronto-cingulate network activation. To test this assumption, a functional magnetic resonance imaging study was conducted in 34 healthy subjects. Univariate and functional connectivity analyses in statistical parametric mapping software 8 were used. Self-referential stimuli and the Stroop task were presented in an event-related design. As hypothesized, rACC was specifically engaged during negative self-referential processing (SRP) and was significantly related to the degree of depressive symptoms in participants. BOLD signal in rACC showed increased valence-dependent (negative vs neutral SRP) interaction with BOLD signal in prefrontal and dorsal anterior cingulate regions during Stroop task performance. This result provides strong support for the notion that enhanced rACC interacts with brain regions involved in cognitive control processes and substantiates our previous interpretation of increased rACC and prefrontal activation in patients during Stroop task.

Investigating the effects of three needling parameters (manipulation, retention time, and insertion site) on needling sensation and pain profiles: a study of eight deep needling interventions

Introduction. In traditional Chinese acupuncture, needle sensation (deqi) is purported to contribute to a therapeutic outcome. While researchers have attempted to define deqi qualitatively, few have examined the effects of needling parameters on its intensity. Methods. 24 healthy subjects completed eight interventions scheduled at least one week apart, which involved manual acupuncture to LI4 or a designated nonacupoint (NAP) on the hand, with real or simulated manipulation each three minutes and needle retentions of one or 21 minutes. Intensities of needling sensation and pain were reported every three minutes and sensation qualities were reported post-intervention. Results. Immediately after needle insertion, similar levels of mean needle sensation and of pain were reported independent of intervention. At subsequent measurement times, only two interventions (one at LI4 and one at NAP) maintained statistically significantly elevated needle sensation and pain scores and reported higher numbers of needle sensation descriptors. For both, the needle was retained for 21 minutes and manipulated every three minutes. Neither intervention differed significantly in terms of levels of pain, and needle sensation or numbers and qualities of needle sensation described. Conclusion. In this group of healthy subjects, the initial needling for all eight interventions elicited similar levels of needle sensation and pain. These levels were only maintained if there was ongoing of needle manipulation and retention of the needle. By contrast, the strength of needle sensation or pain experienced was independent of insertion site.

Thresholds and perception of cold pain, heat pain, and the thermal grill illusion in patients with major depressive disorder

OBJECTIVE

The thermal grill illusion (TGI) in which interlacing cold and warm bars create the illusion of a painful sensation has been suggested as an experimental model for central pain states and pain processing. The aim of this study was to use this technique to gain further insights into the altered pain perception in major depressive disorder (MDD).

METHODS

In 18 unmedicated patients with MDD, cold and heat pain thresholds (CPT/HPT) as well as the perception of the TGI were examined and compared with 18 matched controls.

RESULTS

CPT and HPT were significantly increased in patients (7.9°C and 47.5°C) compared with controls (15.9°C and 45.2°C, respectively; p < .05). In the range of TGI stimuli that were perceived painful by controls, the patients did not indicate painful sensations, thereby indicating a shift of the stimulus-response curve of TGI pain perception toward higher stimulus intensities, that is, greater temperature differentials between cold and warm bars (11.5°C for controls, 16.7°C for patients). The patients rated the pain intensity perceived at the respective pain thresholds (CPT and HPT) in tendency higher than did the controls, whereas they perceived the TGI less painful despite increased stimulus intensities. Unpleasantness ratings were similar between groups.

CONCLUSIONS

CPT, HPT and temperature differentials for the perception of the TGI, were increased in patients with MDD as compared with controls. Pain intensity, however, was rated differently for CPT and HPT, where patients indicated higher ratings in tendency, and for the TGI stimulation, where pain was perceived less intense.

An fMRI study on the acute effects of exercise on pain processing in trained athletes

Endurance exercise is known to promote sustained antinociceptive effects, and there is evidence that the reduction of pain perception mediated by exercise is driven by central opioidergic neurotransmission. To directly investigate the involved brain areas and the underlying neural mechanisms in humans, thermal heat-pain challenges were applied to 20 athletes during 4 separate functional magnetic resonance imaging (fMRI) scans, i.e., before and after 2 hours of running (exercise condition) and walking (control condition), respectively. Imaging revealed a reproducible pattern of distributed pain-related activation in all 4 conditions, including the mesial and lateral pain systems, and the periaqueductal gray (PAG) as a key region of the descending antinociceptive pathway. At the behavioral level, running as compared with walking decreased affective pain ratings. The influence of exercise on pain-related activation was reflected in a significant time × treatment interaction in the PAG, along with similar trends in the pregenual anterior cingulate cortex and the middle insular cortex, where pain-induced activation levels were elevated after walking, but decreased or unchanged after running. Our findings indicate that enhanced reactive recruitment of endogenous antinociceptive mechanisms after aversive repeated pain exposure is attenuated by exercise. The fact that running, but not walking, reproducibly elevated β-endorphin levels in plasma indicates involvement of the opioidergic system in exercise. This may argue for an elevated opioidergic tone in the brain of athletes, mediating antinociceptive mechanisms. Our findings provide the first evidence using functional imaging to support the role of endurance exercise in pain modulation.

Sadness enhances the experience of pain and affects pain-evoked cortical activities: an MEG study

Pain is a multidimensional phenomenon. Previous psychological studies have shown that a person's subjective pain threshold can change when certain emotions are recognized. We examined this association with magnetoencephalography. Magnetic field strength was recorded with a 306-channel neuromagnetometer while 19 healthy subjects (7 female, 12 male; age range = 20-30 years) experienced pain stimuli in different emotional contexts induced by the presentation of sad, happy, or neutral facial stimuli. Subjects also rated their subjective pain intensity. We hypothesized that pain stimuli were affected by sadness induced by facial recognition. We found: 1) the intensity of subjective pain ratings increased in the sad emotional context compared to the happy and the neutral contexts, and 2) event-related desynchronization of lower beta bands in the right hemisphere after pain stimuli was larger in the sad emotional condition than in the happy emotional condition. Previous studies have shown that event-related desynchronization in these bands could be consistently observed over the primary somatosensory cortex. These findings suggest that sadness can modulate neural responses to pain stimuli, and that brain processing of pain stimuli had already been affected, at the level of the primary somatosensory cortex, which is critical for sensory processing of pain.

PERSPECTIVE

We found that subjective pain ratings and cortical beta rhythms after pain stimuli are influenced by the sad emotional context. These results may contribute to understanding the broader relationship between pain and negative emotion.

Impact of depression mood disorder on the adverse drug reaction incidence rate of anticancer drugs in cancer patients

The aim of this study was to explore the impact of depression mood disorder on the incidence of adverse drug reactions of anticancer drugs in cancer patients. The Hamilton Depression Scale 17 was used to evaluate the depression mood disorder level in 73 cancer patients before chemotherapy. Pharmacists monitored adverse drug reactions during the chemotherapy period. The relationship between depression mood disorder level and the incidence of adverse drug reactions was analysed. The frequency and extent of total adverse drug reactions were not related to depression mood disorder level. The frequency and extent of subjectively experienced adverse drug reactions such as anorexia, nausea and fatigue were related to depression mood disorder level. In conclusion, psychological support and intervention should be provided to cancer patients in order to improve patient adherence and cancer chemotherapy effectiveness, and to decrease the incidence of adverse drug reactions.

Pain, sensory function, and neurogenic inflammatory response in young women with low mood

OBJECTIVE

To determine the relationship of mood status to pain complaints, sensory function, neurogenic inflammatory response, and general health in young women.

METHODS

Ninety-three women aged 18-29 participated in the study and were categorized by SCL-90-R depression score into low-mood (n=21) and normal-mood (n=72) groups. All subjects were below the threshold for possible clinical depression.

RESULTS

Low mood was associated with decreased tactile sensitivity, reduced response to topical capsaicin, and increased complaints of back, joint, muscle, and visceral pain, but not headache, when compared to normal mood controls. Low mood was also associated with reported poorer health and physical functioning, increased psychopathology, and family history of mood problems.

CONCLUSION

These data show that even subclinical low mood is associated with marked alterations in health and psychophysiological function.

Sad mood increases pain sensitivity upon thermal grill illusion stimulation: implications for central pain processing

In different fields of neuroscience research, illusions have successfully been used to unravel underlying mechanisms of stimulus processing. One such illusion existing for the field of pain research is the so-called thermal grill illusion. Here, painful sensations are elicited by interlacing warm and cold bars, with stimulus intensities (temperatures) of these bars being below the respective heat pain or cold pain thresholds. To date, the underlying mechanisms of this phenomenon are not completely understood. There is some agreement, however, that the sensation evoked by this stimulation is generated by central nervous interactions. Therefore, we followed two approaches in this study: firstly, we aimed at developing and validating a water-driven device which might be used in fMRI scanners in future studies - subject to minor adaptations. Secondly, we aimed to interfere with this illusion by induction of a sad mood state, a procedure which is suggested to influence central nervous structures that are also involved in pain processing. The newly developed device induced thermal grill sensations similar to those reported in the literature. Induction of sad, but not neutral mood states, resulted in higher pain and unpleasantness ratings of the painful illusion. These findings might be of importance for the understanding of pain processing in healthy volunteers, but putatively even more so in patients with major depressive disorder. Moreover, our results might indicate that central nervous structures involved in the affective domain or cognitive domain of pain processing might be involved in the perception of the illusion.

Pain/Depression dyad: a key to a better understanding and treatment of functional somatic syndromes

Functional somatic syndromes include some of the most common and frustrating illnesses seen by primary care physicians and medical specialists. An extensive literature search of the 2 best characterized functional somatic syndromes, fibromyalgia and irritable bowel syndrome, reveals the overlap of these 2 disorders and their close relationship to depression. New pathophysiologic studies have shown that there are similar central nervous system changes in fibromyalgia, irritable bowel syndrome, and depression. These clinical and biologic similarities are consistent with the observations that the effective management of fibromyalgia and irritable bowel syndrome is comparable to that of depression.

Lower-order pain-related constructs are more predictive of cold pressor pain ratings than higher-order personality traits

Pain is a debilitating condition affecting millions each year, yet what predisposes certain individuals to be more sensitive to pain remains relatively unknown. Several psychological factors have been associated with pain perception, but the structural relations between multiple higher- and lower-order constructs and pain are not well understood. Thus, we aimed to examine the associations between pain perception using the cold pressor task (CPT), higher-order personality traits (neuroticism, negative affectivity, trait anxiety, extraversion, positive affectivity, psychoticism), and lower-order pain-related psychological constructs (pain catastrophizing [pre- and post-], fear of pain, anxiety sensitivity, somatosensory amplification, hypochondriasis) in 66 pain-free adults. Factor analysis revealed 3 latent psychological variables: pain- or body-sensitivity, negative affect/neuroticism, and positive affect/extraversion. Similarly, pain responses factored into 3 domains: intensity, quality, and tolerance. Regression and correlation analyses demonstrated that: 1) all the lower-order pain constructs (fear, catastrophizing, and hypochondriasis) are related through a single underlying latent factor that is partially related to the higher-order negative-valence personality traits; 2) pain- or body-sensitivity was more strongly predictive of pain quality than higher-order traits; and 3) the form of pain assessment is important-only qualitative pain ratings were significantly predicted by the psychological factors.

PERSPECTIVE

Consistent with the biopsychosocial model, these results suggest multiple pain-related psychological measures likely assess a common underlying factor, which is more predictive of qualitative than intensity pain ratings. This information may be useful for the development and advancement of pain assessments and treatments while considering the multidimensional nature of pain.

The influence of negative mood on heart rate complexity measures and baroreflex sensitivity in healthy subjects

BACKGROUND

Decreased cardiac vagal function is linked with increased cardiac mortality and depression is associated with decreased heart rate variability. We have previously shown that the Mood Induction Procedure (MIP) in healthy subjects alters pain perception and thalamic activity during pain perception.

AIM

To study the effect of negative emotion on heart rate variability and complexity measures as well as on baroreceptor sensitivity, as these parameters reflect cardiac autonomic function.

PATIENTS AND METHODS

We studied 20 healthy female controls before and after neutral MIP and 20 healthy female subjects before and after negative MIP. We investigated measures of valence of mood, heart rate variability and complexity and the baroreceptor sensitivity index.

RESULTS

While there was a significant difference in the valence of mood between the neutral and the negative effect condition, there were no significant differences in any of the heart rate or baroreceptor sensitivity measures between the two groups.

CONCLUSIONS

Our findings did not show any significant influence of acute negative MIP on heart rate variability and complexity measures and baroreceptor sensitivity, even though depressive disorder and stress are associated with decreased heart rate variability. These findings are discussed in the context of clinical depression and anxiety and the increased risk for cardiac mortality. In contrast to the presented results here, we have previously shown that MIP in healthy subjects alters pain perception and thalamic activity.

Increased cold-pain thresholds in major depression

Most previous studies indicated that patients suffering from major depressive disorder (MDD) showed a decreased sensitivity for external or skin surface pain, eg, for heat or electrical stimuli, as compared to healthy controls. Here, we investigated cold-pain thresholds in 20 unmedicated patients suffering from MDD and 20 matched controls. We applied the ascending method of limits which has previously been used for heat-pain assessment in patients with depression. Similar to previous results for heat-pain thresholds we found a decreased sensitivity for cold pain in patients with MDD as indicated by increased cold-pain thresholds. This difference was significant on the right arm, whereas only a trend was obtained on the left arm, thus suggesting a certain degree of lateralization, similar to that seen in heat-pain perception in patients suffering from MDD or adjustment disorder. The study confirms our previous results of a lower sensitivity for externally induced pain in patients with MDD. Moreover, it adds weight to the assumption of a lateralized perception of thermal pain in depression.

PERSPECTIVE

This investigation provides further evidence for reduced pain perception of externally applied stimuli in major depression. Thus, central-nervous correlates for this altered pain perception in major depression are worth examining in future studies in order to gain more insight into mechanisms of pain perception on the one hand, and pathology of depression on the other.

Physical fitness and heart rate recovery are decreased in major depressive disorder

OBJECTIVE

To investigate whether physical fitness is decreased in patients with major depressive disorder (MDD) in comparison to matched healthy controls because low physical fitness has been shown to be associated with metabolic syndrome or autonomic dysfunction. Cardiovascular morbidity and mortality are known to be increased in patients with MDD. Furthermore, the effect of a single exhaustive exercise task on heart rate recovery (HRR) and mood was examined.

METHODS

Peak oxygen consumption (VO(2)peak), maximum workload (P peak), and individual anaerobic threshold (IAT) were assessed in 22 patients suffering from MDD and 22 controls in a stepwise exhaustion protocol, using spirometry and lactate diagnostics. HRR was detected within the first minute after recovery. The Self-Assessment Manikin (SAM) was used to assess mood before and after exercise.

RESULTS

VO(2)peak, P peak, and IAT were decreased significantly in patients, indicating reduced physical fitness in MDD as compared with control subjects. A single exercise exhaustion significantly improved mood in patients, but not in controls. Mood improvement in patients correlated with maximum lactate levels. Significantly reduced HRR values in patients further point to an elevated cardiovascular risk profile and autonomic dysfunction.

CONCLUSIONS

Our results indicate reduced physical fitness in patients with MDD. Thus, special training programs should be developed to improve their cardiovascular risk profile. In addition, the intriguing finding of a correlation between lactate levels and mood changes should be followed up in future studies to unravel putative mechanisms.