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Emotions can influence our eating behaviors. Facing an acute stressor or being in a positive mood are examples of situations that tend to modify appetite. However, the question of how the brain integrates these emotion-related changes in food processing remains elusive. Here we designed an emotional priming fMRI task to test if amygdala activity during food pictures differs depending on the emotional context. Fifty-eight female participants completed a novel emotional priming task, in which emotional images of negative, neutral or positive situations were followed by pictures of either foods or objects. After priming in each trial, participants rated how much they liked the shown foods or objects. We analyzed how brain activity during the contrast “foods > objects” changed according to the emotional context – in the whole brain and in the amygdala. We also examined the potential effect of adiposity (i.e., waist circumference). We observed a higher difference between liking scores for foods and objects after positive priming than after neutral priming. In the left amygdala, activity in the contrast “foods > objects” was higher after neutral priming relative to negative priming. Waist circumference was not significantly related to this emotional priming effect on food processing. Our results suggest that emotional context alters food and non-food perception, both in terms of liking scores and with regards to engagement of the left amygdala. Moreover, our findings indicate that emotional context has an impact on the salience advantage of food, possibly affecting eating behavior.

Goal-directed behaviour depends on successful association of environmental cues with reward or punishment. Obesity has been linked to diminished learning success in this domain. In contrast, here we demonstrate superior learning in obese participants independent of reward type. We tested association learning in 85 participants with a wide body-mass-index (BMI) range (lean to obese) in four probabilistic reversal-learning experiments. Experiments differed regarding learning mode (active and passive) and reward stimulus (pictures of snack food and money). Food and monetary rewards were adjusted regarding their motivational value in order to allow a direct comparison of related learning characteristics. Our results reveal enhanced associative learning in obese compared to normal-weight participants – reward-independently for expectancy updating and specifically for food-rewards for initial acquisition. When comparing the influence of continuous BMI in active and passive learning, food reward was associated with opposite effects of BMI on performance. Our data indicate generalized, weight-dependent differences in essential reward-learning, though particularly for food reward. We thereby argue that flexible updating of reward-related information may in fact be enhanced in people with obesity – and, thus, possibly promote unhealthy food choices in modern society.

Much of our behaviour is driven by two motivational dimensions-approach and avoidance. These have been related to frontal hemispheric asymmetries in clinical and resting-state EEG studies: Approach was linked to higher activity of the left relative to the right hemisphere, while avoidance was related to the opposite pattern. Increased approach behaviour, specifically towards unhealthy foods, is also observed in obesity and has been linked to asymmetry in the framework of the right-brain hypothesis of obesity. Here, we aimed to replicate previous EEG findings of hemispheric asymmetries for self-reported approach/avoidance behaviour and to relate them to eating behaviour. Further, we assessed whether resting fMRI hemispheric asymmetries can be detected and whether they are related to approach/avoidance, eating behaviour and BMI. We analysed three samples: Sample 1 (n = 117) containing EEG and fMRI data from lean participants, and Samples 2 (n = 89) and 3 (n = 152) containing fMRI data from lean, overweight and obese participants. In Sample 1, approach behaviour in women was related to EEG, but not to fMRI hemispheric asymmetries. In Sample 2, approach/avoidance behaviours were related to fMRI hemispheric asymmetries. Finally, hemispheric asymmetries were not related to either BMI or eating behaviour in any of the samples. Our study partly replicates previous EEG findings regarding hemispheric asymmetries and indicates that this relationship could also be captured using fMRI. Our findings suggest that eating behaviour and obesity are likely to be mediated by mechanisms not directly relating to frontal asymmetries in neuronal activation quantified with EEG and fMRI.

The perception of body size and thus weight-related stigmatization vary between cultures. Both are stronger in Western than in Polynesian societies. Negative emotional experiences alter one’s behavioral, psychological, and physiological reactions in social interactions. This study compared affective and autonomic nervous system responses to social interactions in Germany and American Samoa, two societies with different body-size related norms. German (n = 55) and Samoan (n = 56) volunteers with and without obesity participated in a virtual ball-tossing game that comprised episodes of social inclusion and social exclusion. During the experiment, heart rate was measured and parasympathetic activity (i.e., high-frequency heart rate variability) was analyzed. We found differences in both emotional experience and autonomic cardio-regulation between the two cultures: during social inclusion, Germans but not Samoans showed increased parasympathetic activity. In Germans with obesity, this increase was related to a more negative body image (comprising high rates of weight-related teasing). During social exclusion, Samoans showed parasympathetic withdrawal regardless of obesity status, while Germans with obesity showed a stronger increase in parasympathetic activity than lean Germans. Furthermore, we found fewer obesity-related differences in emotional arousal after social exclusion in Samoans as compared to Germans. Investigating the interplay of socio-cultural, psychological, and biological aspects, our results suggest influences of body size-related socio-cultural norms on parasympathetic cardio-regulation and negative emotions during social interactions.

Obesity is often accompanied by weight stigmatization; subsequently, individuals with obesity frequently face social rejection. It has been shown that recurrent negative social experiences can alter the perception of social cues. However, the way individuals with obesity process social stimuli is not well understood. This study aims to investigate obesity-related alterations in social compared to nonsocial information processing. Women with obesity (n = 14) and without obesity (n = 14) participated in a social and a monetary incentive delay task in which they anticipated and received positive, negative, and neutral outcomes in the form of faces or money. During the experiment, phasic heart rate changes and reaction times were measured. Women with obesity, compared to lean women, exhibited a stronger differentiation during the anticipation of monetary and social reinforcement, showing slower reaction times to social cues compared to monetary cues. During the outcome processing phase, women with obesity relative to controls demonstrated diminished heart rate responses particularly to negative social outcomes. Interestingly, differences in cardiac responses in participants with obesity were moderated by weight-related teasing experiences. In women with obesity, a higher BMI was associated with blunted cardiac responses to social cues relative to monetary cues only if they reported more emotional pain after weight-related teasing. Our results contribute to a better understanding of social information processing in obesity and give first evidence for the role of negative social experiences in reinforcement processing.

Individuals with obesity are often characterized by alterations in reward processing. This may affect how new information is used to update stimulus values during reinforcement-based learning. Here, we investigated obesity-related changes in non-food reinforcement processing, their impact on learning performance as well as the neural underpinnings of reinforcement-based learning in obesity. Nineteen individuals with obesity (BMI > = 30 kg/m2, 10 female) and 23 lean control participants (BMI 18.5–24.9 kg/m2, 11 female) performed a probabilistic learning task during functional magnetic resonance imaging (fMRI), in which they learned to choose between advantageous and disadvantageous choice options in separate monetary gain, loss, and neutral conditions. During learning individuals with obesity made a significantly lower number of correct choices and accumulated a significantly lower overall monetary outcome than lean control participants. FMRI analyses revealed aberrant medial prefrontal cortex responses to monetary losses in individuals with obesity. There were no significant group differences in the regional representation of prediction errors. However, we found evidence for increased functional connectivity between the ventral striatum and insula in individuals with obesity. The present results suggest that obesity is associated with aberrant value representations for monetary losses, alterations in functional connectivity during the processing of learning outcomes, as well as a decresased reinforcement-based learning performance. This may affect how new information is incorporated to adjust dysfunctional behavior and could be a factor contributing to the maintenance of dysfunctional eating behavior in obesity. Electronic supplementary material The online version of this article (10.1007/s11682-017-9786-8) contains supplementary material, which is available to authorized users.

Current theories state that the hippocampus is responsible for the formation of memory representations regarding relations, whereas extrahippocampal cortical regions support representations for single items. However, findings of impaired item memory in hippocampal amnesics suggest a more nuanced role for the hippocampus in item memory. The hippocampus may be necessary when the item elements need to be bound within and across episodes to form a lasting representation that can be used flexibly. The current investigation was designed to test this hypothesis in face recognition. H.C., an individual who developed with a compromised hippocampal system, and control participants incidentally studied individual faces that either varied in presentation viewpoint across study repetitions or remained in a fixed viewpoint across the study repetitions. Eye movements were recorded during encoding and participants then completed a surprise recognition memory test. H.C. demonstrated altered face viewing during encoding. Although the overall number of fixations made by H.C. was not significantly different from that of controls, the distribution of her viewing was primarily directed to the eye region. Critically, H.C. was significantly impaired in her ability to subsequently recognize faces studied from variable viewpoints, but demonstrated spared performance in recognizing faces she encoded from a fixed viewpoint, implicating a relationship between eye movement behavior in the service of a hippocampal binding function. These findings suggest that a compromised hippocampal system disrupts the ability to bind item features within and across study repetitions, ultimately disrupting recognition when it requires access to flexible relational representations.

Individuals with obesity in Western societies often face weight-related stigmatization and social exclusion. Recurrent exposure to prejudice and negative social feedback alters one's behavior in future social interactions. In this study, we aimed to investigate autonomic nervous system and affective responses to social interactions in individuals with obesity. Women and men with (n = 56) and without (n = 56) obesity participated in episodes of social inclusion and social exclusion using a virtual ball-tossing game. During the experiment, heart rate was measured and parasympathetic activity (overall high-frequency power and event-related cardiac slowing) was analyzed. Our results show that in novel social interactions, women with obesity, relative to the other groups, exhibited the strongest increase in parasympathetic activity. Furthermore, parasympathetic activity was related to a more negative body image in individuals with obesity, but not in lean individuals. Additionally, women with obesity reported a stronger decrease in mood after social exclusion than did the other participants. Our results demonstrate influences of objective and subjective bodily characteristics on parasympathetic cardio-regulation during social interactions. In particular, they show behavioral and physiological alterations during social interactions in women with obesity.

Negative emotional stimuli are particularly salient events that receive privileged access to neurocognitive resources. At the neural level, the processing of negative stimuli relies on a set of sensory, limbic, and prefrontal areas. However, controversies exist on how demographic and task-related characteristics modulate this brain pattern. Here, we used activation likelihood estimation (ALE) meta-analysis and replicator dynamics to investigate the processing of negative visual stimuli in healthy adults. Our findings endorse the central role of the amygdala. This result might reflect how this structure modulates perceptual and attentional mechanisms in response to emotional stimuli. Additionally, we characterize how the neural processing of negative visual stimuli is influenced by the demographic factors of age and sex as well as by task-related characteristics like stimulus type, emotion category, and task instruction, with the amygdala showing comparable engagement across different sexes, stimulus types, and task instructions. Our findings practically inform experimentation in the affective neurosciences but also suggest brain circuits for neurobiological investigations of affective symptomatology.

Obesity is often accompanied by weight stigmatization; subsequently, individuals with obesity frequently face social rejection. It has been shown that recurrent negative social experiences can alter the perception of social cues. However, the way individuals with obesity process social stimuli is not well understood. This study aims to investigate obesity-related alterations in social compared to nonsocial information processing. Women with obesity (n = 14) and without obesity (n = 14) participated in a social and a monetary incentive delay task in which they anticipated and received positive, negative, and neutral outcomes in the form of faces or money. During the experiment, phasic heart rate changes and reaction times were measured. Women with obesity, compared to lean women, exhibited a stronger differentiation during the anticipation of monetary and social reinforcement, showing slower reaction times to social cues compared to monetary cues. During the outcome processing phase, women with obesity relative to controls demonstrated diminished heart rate responses particularly to negative social outcomes. Interestingly, differences in cardiac responses in participants with obesity were moderated by weight-related teasing experiences. In women with obesity, a higher BMI was associated with blunted cardiac responses to social cues relative to monetary cues only if they reported more emotional pain after weight-related teasing. Our results contribute to a better understanding of social information processing in obesity and give first evidence for the role of negative social experiences in reinforcement processing.

Die Adipositas stellt eine der größten medizinischen und soziökonomischen Herausforderungen für unsere modernen Gesundheitssysteme dar. Als wichtige der Adipositas zugrundeliegende Faktoren wurden in früheren Studien typische Verhaltensunterschiede, abweichende hirnmorphologische und -funktionelle Befunde sowie unterschiedliche Aktivitäten in den Anteilen des autonomen Nervensystems im Vergleich adipöser und schlanker Männer und Frauen festgestellt. Diese Unterschiede könnten nach weiterer differenzierter Untersuchung wichtige Ansatzpunkte neuer Therapieformen liefern. In der vorliegenden Studie untersuchten wir Lernperformanz und kardiale Reaktionsmuster während verstärkenden Lernens unter dem Einfluss von Feedback-Valenz, Geschlecht und Adipositas auf Lernleistung und autonome Reaktionen anhand einer probabilistischen Lernaufgabe. Um exakt zwischen dem Lernverhalten bei positivem gegenüber negativem Feedback differenzieren zu können verwendeten wir ein spezielles Aufgaben-Design eines probabilistischen Lernexperiments zur operanten Konditionierung mittels monetären Feedbacks. Neben der Lernleistung untersuchten wir die Unterschiede in der kardialen Reaktivität bei der Verarbeitung der beiden Feedback-Valenzen sowie die Einflüsse von Geschlecht und Adipositas auf diese Prozesse. In der Analyse der Stärke der phasischen kardialen Reaktionen auf die Präsentation von Feedback zeigte sich ein direkter Zusammenhang zur Stärke des Vorhersagefehlers. Dieser kodiert als neuronales Signal für die Neubewertung von kortikalen Werte-Repräsentationen, falls das tatsächliche Ergebnis einer Entscheidung von dem erwarteten Ergebnis abweicht. Folglich bestehen direkte Wechselwirkungen zwischen phasischen Herzraten-Dezelerationen und höheren Prozessen des Feedback-Monitorings, was in der vorliegenden Studie nach unserem besten Wissen erstmalig als direkter Zusammenhang aufgezeigt werden konnte. Die beobachteten geschlechtsabhängigen Defizite bei verstärkendem Lernen waren nicht durch Differenzen in der Aneignung von Wissen, sondern in einer unzureichenden Anwendung des Erlernten begründet. Dabei zeigten besonders weibliche Probanden in der Belohnungsbedingung ein stärker inkonsistentes Verhalten im Vergleich zu männlichen Probanden, was in dieser Aufgabe zu einer geringeren Anzahl an vorteilhaften Entscheidungen führte und damit einer geringeren Lernperformanz. Darüber hinaus liefern unsere Ergebnisse weitere wichtige Hinweise für adipositasspezifische Unterschiede im Lernverhalten. In der initialen Lernphase war der Lernprozess im Vermeiden von Bestrafung bei adipösen Probanden verlangsamt, was im Einklang mit Ergebnissen aus der Literatur zu Einschränkungen in der Vermeidung negativer Langzeit-Folgen steht. Dieser Fund sollte in folgenden Studien differenzierter untersucht werden, um so die Entwicklung geeigneter Therapieformen weiter voran zu treiben.:1. Einführung in die Thematik 1.1 Adipositas 1.2 Lernen 1.3 Adipositasspezifische Lerndefizite 1.4 Geschlechtsunterschiede im Lernverhalten 1.5 Lernen und das autonome Nervensystem 1.6 Adipositasspezifische Veränderungen des autonomen Nervensystems 1.7 Phasische Herzreaktionen – Internet Intervals 1.8 Rationale der Studie 2. Paper 3. Zusammenfassung der Arbeit 3.1 Behaviorale Ergebnisse 3.2 Einfluss der Adipositas auf den Lernvorgang 3.3. Einfluss des Geschlechts auf den Lernvorgang 3.4 Zusammenhänge zwischen physischen Herzreaktionen und dem Lernvorgang 3.5 Schlussfolgerungen 4. Literaturverzeichnis 5. Appendix 5.1 Zusatzmaterial 5.1.1 Herzratenvariabilität (HRV) 5.1.2 Interbeat Intervals (IBIs) 5.3 Selbstständigkeitserklärung 5.4 Lebenslauf 5.5 Danksagung