Depression predicts interpersonal problems partially through the attitude towards social touch.

INTRODUCTION: Depression is associated with difficulties in interpersonal relationships, of which communication is an integral part. Communication can not only be effected by verbal means, but also non-verbally by touch. Against this background, the aim of the present study was to investigate the relationship between depression, interpersonal problems and the attitude towards social touch. METHODS: 147 individuals (115 females; 21-71 years old) seeking treatment in a clinic for outpatient psychotherapy took part in the survey. Three questionnaires evaluating the level of depression (Beck Depression Questionnaire), the degree of interpersonal problems (Inventory of Interpersonal Problems) and the attitude towards social touch (Social Touch Questionnaire, were administered. RESULTS: Highly depressed individuals had a more negative attitude towards social touch than non-to lowly depressed individuals. Highly depressed individuals particularly reported to dislike physical touch by not well-known people, but not by close ones. Highly depressed individuals also reported more interpersonal problems, with the level of depression predicting the degree of interpersonal problems. This relationship was partially mediated by the attitude towards social touch in general and, to a greater extent, by the dislike of physical touch by people not well-known in particular. DISCUSSION: Given the role of social touch in the relationship between depression and interpersonal problems, the attitude towards touch may be taken into consideration in the therapy of depressed patients. We assume that a more positive attitude towards social touch can influence the ability to create and maintain interpersonal relationships.

Heart rate variability is enhanced by long-lasting pleasant touch at CT-optimized velocity.

INTRODUCTION: The present study explores whether long-lasting pleasant touch has positive effects on the stress response, reward sensitivity, mood, and interoceptive awareness. METHODS: 40 participants received either 35min of brush stroking targeting C-tactile fibres (CT) or vibration on the forearm, and rated pleasantness and intensity. Prior and after, stress response (cortisol and heart rate variability), reward sensitivity, mood and interoceptive awareness were measured. RESULTS: Pleasantness decreased over time for both groups, with brush stroking being perceived as more pleasant and intense than vibration. Heart rate variability (SDNN) increased for brush stroking only, and was related to the higher pleasantness and intensity. No significant effect of CT-optimal touch was observed on any of the other measures. DISCUSSION: The beneficial effect of pleasant touch on heart rate variability suggests a neuronal link between CT-fibre stimulation and autonomic regulation, and highlights the potential of long-lasting touch to improve the physiological response.

Touch between romantic partners: Being stroked is more pleasant than stroking and decelerates heart rate.

INTRODUCTION: Touch has been found to entail positive effects in the person receiving it, whereas effects on the person giving touch have previously been unexplored. We investigated whether stroking the partner also is a pleasant experience for the person performing it, and whether it has similar effects on well-being and autonomic nervous function as being stroked or stroking oneself. Furthermore, we compared the hedonic and autonomic nervous effects of stroking the partner and self-stroking. METHODS: In the first experiment, 40 subjects stroked the forearm of their respective partner, while ratings of pleasantness were obtained from both Stroker and Receiver. Heart rate was monitored throughout the session and stroking velocity was tracked. The participants could not see each other faces during the experiment to avoid feedback. In experiment 2, the design was replicated with 20 subjects, and self-stroking and rest conditions were added. RESULTS: Both stroking the partner and self-stroking were performed within a velocity range optimal for activating C-tactile cutaneous afferents. Being stroked, stroking the partner, and self-stroking were all perceived as pleasant. However, being stroked entailed the significantly highest pleasantness ratings, and being stroked was the only condition that significantly decreased heart rate. Individuals in satisfying relationships were more pleased to be touched by their partner and showed a greater decline in heart rate when being touched. DISCUSSION: The data demonstrated a role for affective touch in the regulation of heart rate when being stroked. The absence of autonomic effects when providing the stroking may be due to the absence of visual feedback from the person being stroked. The high pleasantness of giving and receiving touch may foster affective tactile interactions among romantic partners, thus reinforcing the relationship.

Temporal dynamics of brain activation during 40 minutes of pleasant touch.

INTRODUCTION: Touch is important for individuals' subjective well-being, is typically rewarding, and is one of few sensory stimuli which are experienced as pleasant for a rather long time. This study tracked brain activation during slow stroking stimulation of the arm that was applied continuously for 40min - a much longer time than what previous studies have investigated. METHODS: 25 subjects were stroked for 40min with a soft brush while they were scanned with functional Magnetic Resonance Imaging, and rated the perceived pleasantness of the brush stroking. Two resting baselines were included. Whole brain-based analyses investigated the neural response to long-lasting stroking. RESULTS: Stroking was perceived as pleasant throughout scanning and activated areas that were previously found to be involved in the processing of pleasant touch. Activation in primary somatosensory cortex (S1) and S2, subdivision OP1, decreased over time, whereas activation in orbito-frontal gyrus (OFC) and putamen strongly increased until reaching a plateau after approximately 20min. Similarly, functional connectivity of posterior insula with middle cingulate and striatal regions increased over time. DISCUSSION: Long-lasting stroking was processed in similar areas as shorter-lasting stroking. The decreased activation in somatosensory cortices over time may represent stimulus habituation, whereas increased activation in OFC and putamen may relate to the stimulation's subjective reward value. This involvement of reward-related brain circuits can facilitate maintenance of long-lasting social touch interactions.

Emotional Egocentricity Bias Across the Life-Span.

In our daily lives, we often have to quickly estimate the emotions of our conspecifics in order to have successful social interactions. While this estimation process seems quite easy when we are ourselves in a neutral or equivalent emotional state, it has recently been shown that in case of incongruent emotional states between ourselves and the others, our judgments can be biased. This phenomenon, introduced to the literature with the term Emotional Egocentricity Bias (EEB), has been found to occur in young adults and, to a greater extent, in children. However, how the EEB changes across the life-span from adolescence to old age has been largely unexplored. In this study, we recruited 114 female participants subdivided in four cohorts (adolescents, young adults, middle-aged adults, older adults) to examine EEB age-related changes. Participants were administered with a recently developed paradigm which, by making use of visuo-tactile stimulation that elicits conflicting feelings in paired participants, allows the valid and reliable exploration of the EEB. Results highlighted a U-shape relation between age and EEB, revealing enhanced emotional egocentricity in adolescents and older adults compared to young and middle-aged adults. These results are in line with the neuroscientific literature which has recently shown that overcoming the EEB is associated with a greater activation of a portion of the parietal lobe, namely the right Supramarginal Gyrus (rSMG). This is an area that reaches full maturation by the end of adolescence and goes through an early decay. Thus, the age-related changes of the EEB could be possibly due to the life-span development of the rSMG. This study is the first one to show the quadratic relation between age and the EEB and set a milestone for further research exploring the neural correlates of the life-span development of the EEB. Future studies are needed in order to generalize these results to the male population and to explore gender differences related to the aging of socio- emotional processes.

Still Eating Despite Decreased Olfactory Pleasure-The Influence of Odor Liking and Wanting on Food Intake.

Typically, the subjective pleasantness of an odor decreases after it has been repeatedly smelled. This study investigates how the pleasantness ("liking") and the wish to be further exposed to the same odor ("wanting") are affected by variety on a longer time scale, and how they relate to actual food intake. Twenty-five participants rated a coconut odor presented 120 times for its liking and wanting before being offered coconut sweets. The amount eaten was assessed. Individual patterns of change were described by fitting 3 different models to the ratings. To study effects of variety on odor evaluation, the ratings were compared with a previous study where coconut was 1 of 3 odors presented in an alternating way. Initially, both liking and wanting the odors were high, but decreased over repetitions in 75% of the subjects. About 40% of all subjects showed an exponential change of ratings, 40% a step-like change, and 20% a linear change. Food intake was not related to the pattern of change in the ratings. Moreover, decreased olfactory pleasure did not seem to affect eating behavior. However, participants who rated the coconut odor higher at the beginning ate twice as many sweets as the others. Odor variety did not affect the experienced pleasure of smelling (liking), but did affect the motivation to experience the same smell again (wanting). This has not been reported for food or touch stimulation and may be specific for the perception of odors.

Touch satiety: differential effects of stroking velocity on liking and wanting touch over repetitions.

A slow, gentle caress of the skin is a salient hedonic stimulus. Low threshold, unmyelinated C-tactile afferents fire preferentially to this type of touch, where slow (<1 cm/s) and fast (>10 cm/s) stroking velocities produce lower firing frequencies and are rated as less pleasant. The current aim was to investigate how the experience of tactile pleasantness changes with repeated exposure (satiety to touch). A further aim was to determine whether tactile satiety varied with different stroking velocities. The experimental paradigm used a controlled brush stroke to the forearm that was delivered repeatedly for ∼ 50 minutes. In Experiment 1, brush strokes were administered at three different velocities (0.3 cm/s, 3 cm/s and 30 cm/s), which were presented in a pseudo-randomised order. In Experiment 2, brush strokes were applied using only one velocity (either 3 or 30 cm/s). After each stroke, the participants rated both subjective pleasantness (liking) and wanting (the wish to be further exposed to the same stimulus) for each tactile sensation. In Experiment 1, both pleasantness and wanting showed a small, but significant, decrease over repetitions during stroking at 3 cm/s only, where the mean values for pleasantness and wanting were similar. Conversely, slower (0.3 cm/s) and faster (30 cm/s) stroking showed no decrease in ratings over time, however pleasantness was rated higher than wanting. In Experiment 2, both pleasantness and wanting showed a significant decrease over repetitions for both applied velocities, with a larger decrease in ratings for stroking at 3 cm/s. In conclusion, satiety to touch occurred with a slow onset and progression, where pleasantness and wanting ratings to stroking at 3 cm/s were affected more than at the slower or faster velocities. Tactile satiety appears to differ compared to appetitive and olfactory satiety, because the hedonic and rewarding aspects of touch persist for some time.

Liking and wanting pleasant odors: different effects of repetitive exposure in men and women.

Odors can enrich the perception of our environment and are commonly used to attract people in marketing situations. However, the perception of an odor changes over repetitions. This study investigated whether repetitive exposition to olfactory stimuli leads to a change in the perceived pleasantness ("liking") or in the wish to be further exposed to the same olfactory stimulus ("wanting"), and whether these two mechanisms show gender differences. Three different pleasant odors were each repeatedly presented for 40 times in random order with a mean inter-stimulus interval of 18 s. Eighteen participants rated both "liking" and "wanting" for each of the 120 olfactory stimuli. Wanting ratings decreased significantly over repetitions in women and men, with a steeper decrease for men during the initial trials before plateauing. In contrast, liking ratings decreased significantly over repetitions only in men, with a steeper decrease after the initial ratings, but not in women. Additionally, women scored higher in a questionnaire on reward responsiveness than men. We conclude that positive evaluation (liking) and the wish to experience more of the same (wanting) are different concepts even in the domain of olfaction. The persistence of perceived pleasantness in women may be due to the attribution of a greater subjective value to odors.

CT-optimized skin stroking delivered by hand or robot is comparable.

INTRODUCTION: The aim of our study was to investigate whether a pleasant tactile stimulation which is manually produced is qualitatively comparable to an analogous tactile stimulation produced instead by a mechanical source. METHODS: Thirty-one subjects [16 men, 15 women, 24.5 ± 2.6 years, mean, and standard deviation (SD)] were tested under four different conditions in a repeated measurements design. A pleasant caress-like brush stroke on the hairy skin of the forearm was either produced by a robot or by hand with three different velocities (0.3, 3, and 30 cm/s). In two conditions the subjects were informed about the stroke's source, whereas in two different conditions they were not. Subsequent to the stimulation, the subjects were asked to rate both pleasantness and intensity of each tactile sensation. RESULTS: Consistently, pleasantness ratings were very similar in both conditions. This was found across stimulus velocities and regardless of whether the subjects were informed about the source of the on-going stroke or not. In contrast, intensity ratings were significantly higher in the handheld condition for the two slower velocities, but not for the fastest one. CONCLUSION: As robot and human touch are highly comparable in terms of perceived pleasantness, handheld stimulation may be used in studies of touch hedonia where robot stimulation is not applicable (for instance in children or certain body parts).