C-tactile afferent stimulating touch carries a positive affective value

The rewarding sensation of touch in affiliative interactions is hypothesized to be underpinned by a specialized system of nerve fibers called C-Tactile afferents (CTs), which respond optimally to slowly moving, gentle touch, typical of a caress. However, empirical evidence to support the theory that CTs encode socially relevant, rewarding tactile information in humans is currently limited. While in healthy participants, touch applied at CT optimal velocities (1-10cm/sec) is reliably rated as subjectively pleasant, neuronopathy patients lacking large myelinated afferents, but with intact C-fibres, report that the conscious sensation elicited by stimulation of CTs is rather vague. Given this weak perceptual impact the value of self-report measures for assessing the specific affective value of CT activating touch appears limited. Therefore, we combined subjective ratings of touch pleasantness with implicit measures of affective state (facial electromyography) and autonomic arousal (heart rate) to determine whether CT activation carries a positive affective value. We recorded the activity of two key emotion-relevant facial muscle sites (zygomaticus major—smile muscle, positive affect & corrugator supercilii—frown muscle, negative affect) while participants evaluated the pleasantness of experimenter administered stroking touch, delivered using a soft brush, at two velocities (CT optimal 3cm/sec & CT non-optimal 30cm/sec), on two skin sites (CT innervated forearm & non-CT innervated palm). On both sites, 3cm/sec stroking touch was rated as more pleasant and produced greater heart rate deceleration than 30cm/sec stimulation. However, neither self-report ratings nor heart rate responses discriminated stimulation on the CT innervated arm from stroking of the non-CT innervated palm. In contrast, significantly greater activation of the zygomaticus major (smiling muscle) was seen specifically to CT optimal, 3cm/sec, stroking on the forearm in comparison to all other stimuli. These results offer the first empirical evidence in humans that tactile stimulation that optimally activates CTs carries a positive affective valence that can be measured implicitly

Salivary oxytocin mediates the association between emotional maltreatment and responses to emotional infant faces.

Childhood emotional maltreatment has been associated with a higher risk for maltreating one's own offspring. In the current study, we explored a possible role of oxytocin in mediating the association between childhood emotional maltreatment and participants' interpretation of infant facial expressions. Oxytocin levels were measured in 102 female participants using saliva samples. They rated the mood of thirteen infants with happy, sad and neutral facial expressions. Emotional maltreatment indirectly influenced responses to happy infant faces by modulating oxytocin levels: higher self-reported emotional maltreatment was related to higher levels of salivary oxytocin which were in turn related to a more positive evaluation of happy infant expressions, but not to the evaluation of sad infant expressions. Oxytocin receptor polymorphism rs53576 did not moderate the relation between maltreatment experiences and salivary oxytocin levels. Early emotional maltreatment might indirectly affect emotional information processing by altering the oxytonergic system

Dynamic changes in DNA methylation of stress-associated genes (OXTR, BDNF) after acute psychosocial stress

Environmentally induced epigenetic alterations are related to mental health. We investigated quantitative DNA methylation status before and after an acute psychosocial stressor in two stress-related genes: oxytocin receptor (OXTR) and brain-derived neurotrophic factor (BDNF ). The cross sectional study took place at the Division of Theoretical and Clinical Psychobiology, University of Trier, Germany and was conducted from February to August 2009. We included 83 participants aged 61-67 years. Thereof, 76 participants completed the full study procedure consisting of blood sampling before (pre-stress), 10 min after (post-stress) and 90 min after (follow-up) the Trier social stress test. We assessed quantitative DNA methylation of whole-blood cells using Sequenom EpiTYPER. Methylation status differed between sampling times in one target sequence of OXTR (P>0.001): methylation increased from pre- to post-stress (P=0.009) and decreased from post-stress to follow-up (P>0.001). This decrease was also found in a second target sequence of OXTR (P=0.034), where it lost statistical significance when blood cell count was statistically controlled. We did not detect any time-associated differences in methylation status of the examined BDNF region. The results suggest a dynamic regulation of DNA methylation in OXTR-which may in part reflect changes in blood cell composition-but not BDNF after acute psychosocial stress. This may enhance the understanding of how psychosocial events alter DNA methylation and could provide new insights into the etiology of mental disorders

Prevalence and Risk Factors for Early, Undesired Weaning Attributed to Lactation Dysfunction

Background: Breastfeeding durations in the United States fall short of public health objectives. We sought to quantify the prevalence and identify risk factors for early, undesired weaning that mothers attribute to physiologic difficulties with breastfeeding. Methods: We analyzed data from the Infant Feeding Practices Study (IFPS) II, a longitudinal study of US women. We defined disrupted lactation as early, undesired weaning attributed to at least two of the following three problems: breast pain, low milk supply, and difficulty with infant latch. We used logistic regression to estimate the association maternal body mass index (BMI), postpartum depressive symptoms, and disrupted lactation. Results: Of 4,902 women enrolled in the IFPS II, we analyzed 2,335 women who reported prenatal intention and breastfeeding initiation. The prevalence of disrupted lactation was 12 per 100 women (95% confidence interval [CI] 11, 13) during the first year of life. Women in this group weaned earlier (median 1.2 months, interquartile range [IQR] 0.5–2.8) than women without disrupted lactation (median 7.0 months, IQR 2.8–2.0, p<0.01). In multivariable-adjusted (MV-adj.) models, we found increased odds of disrupted lactation among overweight (odds ratio [OR] 1.6, 95% CI 1.1–2.3) or obese (OR 1.7, 95% CI 1.2–2.6) women, compared with women with a normal pregravid BMI. Maternal depressive symptoms at 2 months, defined as Edinburgh Postnatal Depression Scale ≥13, were also associated with disrupted lactation (MV-adj. OR 1.7, 95% CI 1.1–2.7). Conclusion: In a longitudinal sample of US women, disrupted lactation affected one in eight mothers who initiated breastfeeding. These findings underscore the need for both improved early breastfeeding support and targeted research to define the underlying pathophysiology and to determine management strategies that will enable more mothers to achieve their breastfeeding goals