Stress-Induced Allodynia – Evidence of Increased Pain Sensitivity in Healthy Humans and Patients with Chronic Pain after Experimentally Induced Psychosocial Stress

Background: Experimental stress has been shown to have analgesic as well as allodynic effect in animals. Despite the obvious negative influence of stress in clinical pain conditions, stress-induced alteration of pain sensitivity has not been tested in humans so far. Therefore, we tested changes of pain sensitivity using an experimental stressor in ten female healthy subjects and 13 female patients with fibromyalgia. Methods: Multiple sensory aspects of pain were evaluated in all participants with the help of the quantitative sensory testing protocol before (60 min) and after (10 and 90 min) inducing psychological stress with a standardized psychosocial stress test (“Trier Social Stress Test”). Results: Both healthy subjects and patients with fibromyalgia showed stress-induced enhancement of pain sensitivity in response to thermal stimuli. However, only patients showed increased sensitivity in response to pressure pain. Conclusions: Our results provide evidence for stress-induced allodynia/hyperalgesia in humans for the first time and suggest differential underlying mechanisms determining response to stressors in healthy subjects and patients suffering from chronic pain. Possible mechanisms of the interplay of stress and mediating factors (e.g. cytokines, cortisol) on pain sensitivity are mentioned. Future studies should help understand better how stress impacts on chronic pain conditions

A Permanent-Magnet Array to Maintain 3He Gas Polarization Inside a Glass Vessel for Applications in High-Energy Laser Physics

We designed and tested an array of permanent magnets (PMA) consisting of two rings with a Halbach-type magnetization pattern, which are stacked at an optimum distance such that its field homogeneity is sufficiently high to maintain the nuclear polarization of 3He gas for future laser experiments. The design included the magnetic layout, the selection of appropriate magnets, and the calculation of the expected relaxation time for the polarized gas. After assembly, we measured the magnetic field in the center region of the PMA. We transferred polarized gas samples from the magnetized transport box into the PMA and determined the relaxation time with four magnetic field sensors in a gradiometric arrangement, detecting the decay of the stray field of the polarized gas on the order of 100 nT in a background field of 1.3 mT. The extracted polarization lifetime of about 21 h is sufficient for the planned experiments at high-power laser facilities

Changes of QST dimensions under stress.

<p>QST  =  Quantitative Sensory Testing, GLM  =  general linear model, CDT  =  cold detection threshold, WDT  =  warm detection threshold, CPT  =  cold pain threshold, HPT  =  heat pain threshold, MPT  =  mechanical pain threshold, WUR  =  wind-up ratio, PPT  =  pressure pain threshold. * Data were log-transformed before analysis.</p

Experimental procedure.

<p>QST  =  Quantitative Sensory Testing, VAS  =  Subjects’ rating of anxiety (healthy controls and FMS) and clinical pain (FMS only) on a visual analogue scale, ECG  =  Recording of stress-induced changes of the heart rate and sympathovagal balance, TSST  =  Trier Social Stress Test.</p

Demographic and clinical characteristics of the participants.

<p>BDI  =  Beck Depression Inventory, STAI  =  Spielberger State-Trait Anxiety Inventory, CTQ  =  Childhood Trauma Questionnaire, TICS  =  Trierer Inventory of Chronic stress.</p

Emotional and cardiac effects of the experimental stressor (TSST).

<p>HR  =  heart rate, SVB  =  sympathovagal balance, VAS  =  visual analogue scale.</p

Changes of sensory pain thresholds (QST) during experimentally induced stress in healthy subjects (HC) and patients with fibromyalgia syndrome (FMS).

<p>CDT  =  cold detection threshold, WDT  =  warm detection threshold, CPT  =  cold pain threshold, HPT  =  heat pain threshold, MPT  =  mechanical pain threshold, WUR  =  wind-up ratio, PPT  =  pressure pain threshold, HC  =  healthy controls, FMS  =  fibromyalgia patients.</p

Differences Between Self-Assessment and External Rating of Voice With Regard to Sex Characteristics, Age, and Attractiveness

Objectives. This study investigates differences between the self-assessment and external rating of a person's voice with regard to sex characteristics, age, and attractiveness of the voice and mean fundamental frequency (F-0). Study Design. Cross-sectional study. Methods. A group of 47 participants with a balanced sex distribution was recruited and the following data were collected: videostroboscopy, voice range profile, F-0, self-assessment questionnaire (attractiveness, masculinity or femininity of voice, and appearance), Voice Handicap Index, and questionnaires to determine levels of depression and quality of life. External rating was performed by four experts and four laymen. Results. In both sexes, fair to moderate significant correlations between the self-assessment of masculinity (men)/femininity (women) of voice and masculinity/femininity of appearance could be found, but not between the self-assessment of attractiveness of voice and appearance. In men, a statistically significant correlation was found between external ratings and self-assessment of attractiveness and, with the exception of the female rating group, of masculinity. In women, self-assessment of femininity and attractiveness of voice did not correlate to a statistically significant extent with the evaluation of the external rater. Additionally, the statistical correlation between estimated and real ages was high. Conclusions. Although the objective parameters of age and gender identification could be rated with a high degree of accuracy, subjective parameters showed significant differences between self-assessment and external rating, in particular in rating women's voices. Taking these findings into account in treatments for modifying voice could impede successful interventions. As one consequence, we recommend summarizing target agreements in detail before the treatment