Sonja Übel

Appetite regulation during food cue exposure: a comparison of normal-weight and obese women.

Obese individuals react to cues of high caloric food with enhanced craving and brain reward system activation. In the present study, we analyzed neural correlates of craving regulation and expected a regulatory deficit in obesity. We conducted an event-related functional magnetic resonance imaging study, where 12 obese women and 14 normal-weight women were exposed to pictures depicting high-caloric food and non-food items. The participants were instructed to either passively look at the pictures, or to regulate (increase, decrease) their appetite. During the passive viewing of food cues, the obese participants showed greater insula activation than the lean participants. Moreover, the obese group displayed stronger dorsolateral prefrontal cortex involvement when attempting to attenuate food-elicited craving. Our data point to an enhanced food cue reactivity and a more effortful strategy for appetite control in obese individuals.

Disgust regulation via placebo: an fMRI study

The present fMRI study investigated whether placebo treatment can change disgust feelings. Disgust-prone women underwent a retest design where they were presented with disgusting, fear-eliciting and neutral pictures once with and once without a placebo (inert pill presented with the suggestion that it can reduce disgust symptoms). The placebo provoked a strong decrease of experienced disgust, which was accompanied by reduced insula activation. Exploratory psychophysiological interaction analyses revealed decreased connectivity in a network consisting of the insula, the amygdala, the anterior cingulate cortex and the orbitofrontal cortex. Moreover, the placebo increased amygdala-DMPFC coactivation. Our findings suggest that placebo use can modulate a specific affective state and might be an option as a first therapy step for clinical samples characterized by excessive and difficult-to-control disgust feelings.

Placebo treatment can alter primary visual cortex activity and connectivity.

Placebo treatment can alter brain activation in regions implicated in affective processing and cognitive control of emotions. This functional magnetic resonance imaging (fMRI) study investigated whether a placebo can additionally modulate visual cortex activity and connectivity during affective picture perception. The participants underwent a retest design where they were presented with disgusting, fear-eliciting and neutral pictures both with, and without a placebo (inert pill presented with the suggestion that it can reduce disgust symptoms). The placebo provoked a strong decrease in experienced disgust. This was accompanied by a reduced activation of the primary visual cortex, which showed reduced interaction with the amygdala and the insula. Accordingly, placebos are able to affect basic perceptive processes.

Do not think about pain: Neural correlates of attention guiding during visual symptom provocation in dental phobia—An fMRI study

Patients undergoing dental treatment employ different attentional strategies. In order to investigate associated neuronal correlates, we exposed 20 women suffering from dental phobia and 20 non-anxious women to disorder-related and unrelated pictures. They were asked to either direct their attention to a foreground stimulus in the image (distraction), to classify the content, or to judge whether the picture elicited fear of pain. The patients rated the majority of dental pictures as pain-relevant (84%) in contrast to the control group (12%). Observed group differences were restricted to the pain condition with enhanced orbitofrontal cortex (OFC) activation displayed by the patients. For the controls, OFC and amygdala activity were positively correlated with self-reported dental anxiety during attention to pain. Across both groups, pain focusing provoked increased amygdala recruitment. As the OFC and amygdala are central for the evaluation of threat signals, the mere thinking about the possible pain relevance of stimuli seems to be dysfunctional.

Testing the effects of a disgust placebo with eye tracking.

Previous neuroimaging research showed that a disgust placebo (inert pill presented with the verbal suggestion of disgust relief) reduced visual cortex activation during the viewing of disgust-inducing images. In order to investigate whether this effect of automatic emotion regulation was associated with changed visual scanning patterns of the pictures, we conducted two eye tracking experiments. In the first study, 23 women underwent a retest design during which they passively viewed images depicting disgusting, fear-eliciting, neutral items and fractals both with, and without a placebo. The placebo provoked a substantial decrease in experienced disgust. Although none of the recorded eye movement parameters (number of fixations, fixation duration, saccade amplitude, blinking rate) showed placebo-related changes, placebo effects were suggested by an analysis of spatial fixation patterns. In the second study, which focused on attentional (dis)engagement, 46 women looked at two pictures which were presented side-by-side on the screen. These picture pairs (disgust-neutral, neutral-neutral) were once viewed with and once without a placebo. The placebo again provoked a marked decrease of experienced disgust and enhanced the number of fixations for disgusting images. This change might reflect a greater willingness of the participants to view these stimuli while on the placebo.

Emotion-specific nocebo effects: an fMRI study

The neurobiological mechanisms of nocebos are still poorly understood. Thirty-eight women participated in a ‘smell study’ using functional magnetic resonance imaging. They were presented with an odorless stimulus (distilled water) together with the verbal suggestion that this fluid has an aversive odor which enhances disgust feelings. The nocebo was presented while the participants viewed disgusting, fear-inducing, and neutral images. Participants’ affective and neuronal responses during nocebo administration were compared with those in a control condition without nocebo. Twenty-nine women (76%) reported perceiving a slightly unpleasant and arousing odor. These ‘nocebo responders’ experienced increased disgust during the presentation of disgusting images in combination with the nocebo and showed enhanced left orbitofrontal cortex (OFC) activation. It has been suggested that the OFC is involved in the generation of placebo/nocebo-related expectations and appraisals. This region showed increased functional connectivity with areas involved in interoception (insula), autobiographical memories (hippocampus), and odor imagery (piriform cortex) during nocebo administration. The nocebo-induced change in brain activation was restricted to the disgust condition. Implications for psychotherapy are discussed.

Increased emotional reactivity to affective pictures in patients with skin-picking disorder: Evidence from functional magnetic resonance imaging

The predominant symptom of skin-picking disorder (SPD) is the recurrent picking of ones own skin, leading to tissue damage and discomfort. Psychological disorder models suggest an enhanced emotional reactivity in patients with SPD, which contributes to the maintenance of symptoms. This functional magnetic resonance imaging (fMRI) experiment analyzed both subjective and neuronal responses to affective pictures (categories: fear, disgust, happiness, neutral) in 19 women with SPD and 16 healthy controls. Also, affective traits (disgust, anxiety, depression) were assessed. Those with SPD scored higher on trait anxiety/depression, and reported higher intensities of negative emotions experienced during the picture viewing. On the neuronal level, the clinical group showed enhanced localized brain activation to fear, disgust and happiness in the amygdala, the insula and the orbitofrontal cortex. These regions are part of a brain circuit mediating affective responses and affective awareness. The current fMRI study provides first data on the neuronal basis of elevated emotional reactivity to affective pictures in SPD.

Electrocortical effects of a disgust placebo in children.

The electroencephalogram has been widely used to study voluntary emotion regulation (ER), whereas automatic ER has hardly been investigated. This experiment focused on automatic changes of disgust feelings and event-related potentials due to placebo treatment. Twenty-eight disgust-prone 8- to 13-year-old girls were presented with disgusting, fear-eliciting and neutral pictures once with and once without a placebo (syrup presented with the suggestion that it is able to ease disgust symptoms). In the disgust condition, the placebo reduced experienced disgust and increased frontal late positivity (400-1000 ms after picture onset). A similar electrocortical placebo effect was obtained for the fear pictures. These findings suggest that the placebo had the function of a safety signal which helped the children to direct their automatic attention to the aversive stimuli and to overcome visual avoidance. Future studies should integrate behavioral designs and should use additional psychophysiological measures (e.g., eye-tracking) in order to substantiate this interpretation.

Neuronal responses to the scratching and caressing of one's own skin in patients with skin-picking disorder

Skin‐picking disorder (SPD) is a common mental disorder. The predominant symptom involves the repeated scratching and picking of ones own skin. This behavior causes severe tissue damage (sores, scars, and infections), often leading to disfigurement. Besides physical injury, SPD is associated with clinically significant distress and impairment in important areas of functioning. The neurobiological mechanisms of SPD are still poorly understood. In this study, 30 SPD patients and 31 control participants (35 women, 26 men) with a mean age of 34 years were instructed to either scratch or gently stroke a small skin area on their arms during functional magnetic resonance imaging. Gender‐specific effects were revealed. In the female sample, SPD patients showed less activation in the middle frontal gyrus (MFG) and primary/secondary somatosensory cortices during caressing relative to scratching than controls. In addition, contrasting caressing with a rest condition revealed reduced activation in the somatosensory cortex (concerned with the decoding and integration of tactile information) and the MFG (attention/cognitive monitoring) in female patients. No differential brain activation was found in the male sample. This symptom provocation study hints at a reduced sensitivity of pleasant touch in women with SPD.

Visual symptom provocation in skin picking disorder: an fMRI study

Skin-picking disorder (SPD) is a common mental disorder characterized by recurrent and excessive picking of dermatological irregularities. Different disorder models have been developed to explain this behavior, but empirical evidence is still scarce. One model (the disgust-related disease avoidance model) suggests that SPD might be understood as pathological grooming elicited by skin imperfections that singal possible infection. Twenty-five women with SPD and 19 matched controls viewed and rated images depicting skin irregularities and smooth skin during functional magnetic resonance imaging. The participants did not engage in picking behavior. Relative to controls, SPD patients reported more disgust and urge to pick when looking at skin irregularities. This was accompanied by greater activation in the insula and amygdala, and stronger insula-putamen coupling. Disgust feelings elicited by viewing skin irregularities were positively correlated with activation of the insula and the putamen, in the clinical group. On personality questionnaires, the SPD patients reported elevated self-loathing and problems in regulating their disgust feelings. The current study provides first evidence for altered disgust processing in SPD patients.