Brain mechanisms for processing caress-like touch in skin-picking disorder.

Skin-picking disorder (SPD) is characterized by repetitive touching and picking of one's skin. The picking is typically experienced as pleasant although this behavior leads to tissue damage. The present functional magnetic resonance imaging (fMRI) study investigated how individuals with SPD react to caress-like touch, which stimulates C-tactile afferents. A standardized touch procedure was used. Seventy females with a primary diagnosis of SPD and 62 healthy females received CT-optimal brushing of their forearms (3 cm/s) and non-optimal brushing (30 cm/s) during an fMRI session. The two types of tactile stimulation were rated according to pleasure, arousal, and urge to pick one's skin. Relative to healthy controls, patients with SPD showed greater activation in parietal regions (supramarginal/angular gyrus) during CT-optimal touch. Moreover, the deactivation of the middle/ inferior frontal cortex displayed by control participants was absent in the SPD group. Being touched was rated as less pleasant, more arousing, and elicited a greater urge to perform skin-picking in participants with SPD. The mentioned frontal and parietal brain regions are sources of attentional control. They are involved in integrating somatosensory information and switching attention between external/internal stimuli. The present study adds to the limited database on the dysfunctional processing of touch in SPD. This study was preregistered on the German Clinical Trials Register (DRKS00022123, June 8th, 2020).

Reduction of Pathological Skin-Picking Via Expressive Writing: A Randomized Controlled Trial.

Background: Expressive writing (EW: a personal form of writing about emotional distress, without regard to writing conventions) can improve physical and mental health. The present study investigated whether EW can reduce pathological skin-picking. In addition, the effects of two modalities of writing were contrasted with each other: computer vs. paper/pencil. Method: A total of 132 females with self-reported pathological skin-picking participated in a two-week intervention. They either carried out six EW sessions or wrote about six abstract paintings (control condition), using either paper/pencil or a computer. Before and after each session, participants rated their affective state and the urge to pick their skin via a smartphone application. Questionnaires for assessing skin-picking severity were completed before and after the two-week intervention. Results: The urge for skin-picking decreased directly after a writing session. The reduction was more pronounced in participants of the EW group, who also experienced reduced tension and increased feelings of relief at the end of a writing session. EW also reduced the severity of focused skin-picking after the two-week intervention. The writing modality had no differential effect on skin-picking symptoms. Conclusions: This study identified beneficial effects of EW on pathological skin-picking. A future study could investigate EW as a potential tool in the context of (online) psychotherapy for skin-picking disorder.

Evaluation of Affective Touch: A Comparison Between Two Groups of Younger and Older Females.

BACKGROUND: Caress-like touch activates C-tactile (CT) afferents present in the skin of humans. It is generally assumed that this type of touch provides beneficial effects throughout the lifespan. However, little is known about its processing in later adulthood. Moreover, emotional responses to interpersonal vs. self-touch have not been investigated in older adults. METHOD: A total of 132 females from two age groups (older: 60-96 years; younger: 18-30) participated in a well-validated method of tactile stimulation, in which CT-optimal vs. nonoptimal soft brushing (3 cm/s vs. 30 cm/s) was administered on the forearms of the participants, once by a female experimenter and once by the participant themselves. All participants rated their affective state in each of the conditions and tactile acuity was assessed. RESULTS: Relative to the younger group, older participants rated touch as more pleasant, independent of type (CT-optimal, non-optimal) and origin (experimenter, self). In the older group, the emotional differentiation of CT-optimal vs. non-optimal touch was reduced, which was associated with reduced tactile acuity. CONCLUSION: This study revealed an age-dependent enhancement of the perceived pleasantness of (self)touch. Interventions with auditory-guided CT-optimal self-touch could be easily implemented as part of training programs for older adults.

Olfactory imagery as a retrieval method for autobiographical memories.

INTRODUCTION: The retrieval of autobiographical memories is influenced by several factors, such as sensory modality and the emotional salience of memory cues. This study aimed at investigating the interaction between sensory modalities (olfaction, vision) and emotional dimensions (valence, arousal) of imagery cues, on the frequency, quality, and age distribution of the autobiographical memories (AMs) elicited. METHOD: A total of 296 females (aged between 18 and 35 years) received one out of eight brief instructions for olfactory or visual imagery. The participants were asked to create a mental image with either high arousal/positive valence, high arousal/negative valence, low arousal/positive valence, or low arousal/negative valence (e.g., 'imagine an unpleasant and arousing odor/scene'); no specific stimulus was mentioned in the instruction. RESULTS: The approach used elicited imagery with autobiographical content in the majority of participants (78%). In terms of frequency, odor imagery, compared to visual imagery, turned out to be more effective at retrieving either unpleasant memories associated with experiences in adulthood, or pleasant childhood memories. In terms of quality, the imagery was rated as less vivid in the olfactory compared to the visual condition (irrespective of valence and arousal of the imagery instruction). Visual imagery was associated with the experience of more diverse emotions (happiness, sadness, anxiety, anger) than odor imagery, which was related primarily with disgust and happiness. CONCLUSION: Our findings indicate that nonspecific imagery induction is a useful approach in accessing AM. IMPLICATION: This approach presents promising clinical applications, such as in working with autobiographical memory narratives in psychotherapy.

Reduced Olfactory Memory Performance Is Associated with Executive Function Deficits in Older Adults.

INTRODUCTION: Previous research has identified an association between olfactory impairment (reduced odor sensitivity/ identification/ discrimination) and cognitive impairment in older adults. The present study focused on the relationship between olfactory memory performance and cognitive/affective functioning. METHOD: Recognition performance for olfactory and visual stimuli (control condition) was tested through a matching task in older adults (n = 44; Mage = 76 years) and younger adults (n = 56; Mage = 24 years). Additionally, negative affect (anxiety, depression) and cognitive functioning were assessed via validated questionnaires and a neuropsychological test battery. RESULTS: The older participants performed worse than the younger adults in the olfactory memory task. In older adults, difficulties in remembering odors were associated with reduced odor identification and executive functioning (reduced cognitive flexibility). Affective well-being was not related to olfactory memory performance. IMPLICATION: Olfactory memory impairment in older adulthood might be a marker for cognitive decline in areas related to executive functions.

A neurobiological evaluation of soft touch training for patients with skin-picking disorder.

BACKGROUND: Individuals with skin-picking disorder (SPD) display reduced neural sensitivity to slow/soft touch. This functional magnetic resonance imaging (fMRI) study investigated the effects of Soft Touch Training (STT) on neural correlates of touch processing and SPD symptoms. METHOD: Females with a primary diagnosis of SPD (n = 57) were randomly assigned to receive either four weeks of STT (guided soft brushing of selected skin regions) or Progressive Muscle Relaxation (PMR) training (guided tensing and relaxing of selected muscle regions). The app-assisted intervention consisted of 15-minute daily training sessions at home. Before and after the four-week intervention, the two groups participated in a standardized tactile stimulation procedure during fMRI (affective vs nonaffective touch of the forearm). Intervention-based changes in subjective and neural responses to the tactile stimulation as well as SPD severity were compared between the groups. RESULTS: STT increased the pleasantness ratings for (affective) touch administered during fMRI, which was accompanied by decreased activation in the parietal operculum (PO) and supramarginal gyrus (SMG), as well as increased PO-SMG connectivity. These findings possibly reflect normalized affective touch processing due to STT. Both interventions (STT and PMR) reduced SPD severity. CONCLUSIONS: This study demonstrated that a brief app-assisted touch training can change the experience of receiving touch from others and the associated brain activity and connectivity. Adaptations of the training relating to duration/ frequency of sessions might enhance its effectiveness.

The association between local brain structure and disgust propensity.

Research has discovered structural differences in the brains of people with different personality types. In the present voxel-based morphometry study we focused on the association between disgust propensity (DP: the temporally stable tendency to experience disgust across different situations) and grey matter volume (GMV) in regions of interest [insula, orbitofrontal cortex (OFC), basal ganglia]. We collected structural brain scans from 498 healthy individuals (352 females, 146 males; mean age = 27 years). Regression analyses were performed to test the association between three domains of DP (core, animal-reminder, contamination) and GMV. We observed negative correlations between animal-reminder DP and the volume of the insula, and contamination DP and OFC volume. Animal-reminder DP correlated positively with GMV in the basal ganglia (putamen). This study identified weak correlations between local brain volume and disgust propensity. The association between DP and insula volume concerned the posterior insula and was in the opposite of the expected direction. The findings of this study are inconsistent with the concept of the anterior insula as a region that specifically mediates DP.

Disgust-Related Memory Bias in Children and Adults.

Studies with adults found a memory bias for disgust, such that memory for disgusting stimuli was enhanced compared to neutral and frightening stimuli. We investigated whether this bias is more pronounced in females and whether it is already present in children. Moreover, we analyzed whether the visual exploration of disgust stimuli during encoding is associated with memory retrieval. In a first recognition experiment with intentional learning, 50 adults (mean age; M = 23 years) and 52 children (M = 11 years) were presented with disgusting, frightening, and neutral pictures. Both children and adults showed a better recognition performance for disgusting images compared to the other image categories. Males and females did not differ in their memory performance. In a second free recall experiment with eye-tracking, 50 adults (M = 22 years) viewed images from the categories disgust, fear, and neutral. Disgusting and neutral images were matched for color, complexity, brightness, and contrast. The participants, who were not instructed to remember the stimuli, showed a disgust memory bias as well as shorter fixation durations and longer scan paths for disgusting images compared to neutral images. This "hyperscanning pattern" correlated with the number of correctly recalled disgust images. In conclusion, we found a disgust-related memory bias in both children and adults regardless of sex and independently of the memorization method used (recognition/free recall; intentional/incidental).

Effects of Coloring Food Images on the Propensity to Eat: A Placebo Approach With Color Suggestions.

BACKGROUND: Research findings on the appetite-enhancing effect of the color red and the appetite-reducing effect of blue have been inconsistent. The present study used a placebo approach and investigated whether verbal suggestions can enhance color-appetite effects. METHOD: A total of 448 women participated in two experiments. They viewed images with differently colored sweet foods (original color, blue, red, colorless (black-and-white); experiment 1; n = 217) or sweet foods on blue, red, white, and gray backgrounds; experiment 2; n = 231). Before viewing the images, half of the participants received information about the effects of red and blue food color on appetite (color suggestion). The other half received no suggestion. For each of the experiments, the reported propensity to eat (food wanting) was compared between the conditions. RESULTS: All colored food items were associated with a lower propensity to eat compared to the food items in the original color. The color suggestion (compared to no suggestion) additionally decreased the propensity to eat blue and black-and-white food items. Colored backgrounds did not influence food wanting. CONCLUSION: This study demonstrated that red and blue coloring of visual food cues did not have the predicted effects on food wanting. However, the combination of specific food colors with specific color suggestions might be useful to change the willingness to eat sweet products.

Information About the Optimism of a Placebo/Nocebo Provider and Placebo/Nocebo Side Effects.

BACKGROUND: Research has demonstrated that personality characteristics, such as optimism are associated with placebo/nocebo responding. The present study investigated whether written information about the optimism of a placebo/nocebo provider can influence the occurrence of reported placebo/nocebo side effects. METHOD: We analyzed data from 201 females (mean age = 26 years) who participated in a "clinical study on a new massage oil with stone clover extract." The oil (sunflower oil) was introduced as either eliciting a negative side effect (unpleasant itching; "nocebo oil") or a positive side effect (pleasant tingling; "placebo oil"). The administration of the oil was combined with written information about the maker of the product. The oil maker was either portrayed as a very optimistic person or no personal information was provided (only the company name). The participants had no personal contact with the experimenter and received all materials and instructions per post. RESULTS: The participants reported more frequent and intense itching when they received a nocebo suggestion compared to a placebo suggestion. Positive tingling sensations were reported more frequently than itching but did not differ between the placebo/nocebo conditions. Information about the optimism of the oil maker was associated with a lower frequency of reported side effects (adverse and beneficial). CONCLUSION: This study demonstrated that it is sufficient to provide participants with written information about an inert substance to elicit the suggested side effect. Information about the provider's optimistic personality did not specifically influence reported side effects. Future studies should focus on how to adapt written information about a drug/product to minimize adverse side effects and to maximize positive side effects.

Altered grey matter volume in 'super smellers'.

'Super smellers' are those individuals who show a heightened sense of smell. Data on the structural neuroanatomy of this phenomenon are still missing. A voxel-based morphometry study was conducted in order to compare gray matter volume (GMV) in specific brain regions of the olfactory network (piriform/entorhinal cortex, orbitofrontal cortex, insula, hippocampus) between 25 male 'super smellers' and 20 normosmic men. Participants were assigned to these groups based on their scores on a standardized olfactory performance test. Relative to normosmic men, 'super smellers' showed increased GMV in the anterior insula and in the hippocampus (dentate gyrus). These regions are crucial for the integration of olfactory information as well as odor learning and odor memory. Moreover, positive correlations between hippocampal volume and olfactory performance were detected in both groups. Future research should elaborate on how much of the observed neuroanatomical pattern of 'super smellers' is genetic and how much of it reflects experienced-based GMV increase.