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Sustained anticipatory anxiety is central to Generalized Anxiety Disorder (GAD). During anticipatory anxiety, phasic threat responding appears to be mediated by the amygdala, while sustained threat responding seems related to the bed nucleus of the stria terminalis (BNST). Although sustained anticipatory anxiety in GAD patients was proposed to be associated with BNST activity alterations, firm evidence is lacking. We aimed to explore temporal characteristics of BNST and amygdala activity during threat anticipation in GAD patients. Nineteen GAD patients and nineteen healthy controls (HC) underwent functional magnetic resonance imaging (fMRI) during a temporally unpredictable threat anticipation paradigm. We defined phasic and a systematic variation of sustained response models for blood oxygen level-dependent responses during threat anticipation, to disentangle temporally dissociable involvement of the BNST and the amygdala. GAD patients relative to HC responded with increased phasic amygdala activity to onset of threat anticipation and with elevated sustained BNST activity that was delayed relative to the onset of threat anticipation. Both the amygdala and the BNST displayed altered responses during threat anticipation in GAD patients, albeit with different time courses. The results for the BNST activation hint towards its role in sustained threat responding, and contribute to a deeper understanding of pathological sustained anticipatory anxiety in GAD.
Humans in our environment are of special importance to us. Even if our minds are
fixated on tasks unrelated to their presence, our attention will likely be drawn
towards other people’s appearances and their actions.
While we might remain unaware of this attentional bias at times, various studies have demonstrated the preferred visual scanning of other humans by recording eye movements in laboratory settings. The present thesis aims to investigate the circumstances under and the mechanisms by which this so-called social attention operates.
The first study demonstrates that social features in complex naturalistic scenes are prioritized in an automatic fashion. After 200 milliseconds of stimulus presentation, which is too brief for top-down processing to intervene, participants targeted image areas depicting humans significantly more often than would be expected from a chance distribution of saccades. Additionally, saccades towards these areas occurred earlier in time than saccades towards non-social image regions. In the second study, we show that human features receive most fixations even when bottom-up information is restricted; that is, even when only the fixated region was visible and the remaining parts of the image masked, participants still fixated on social image regions longer than on regions without social cues. The third study compares the influence of real and artificial faces on gaze patterns during the observation of dynamic naturalistic videos. Here we find that artificial faces, belonging to humanlike statues or machines, significantly predicted gaze allocation but to a lesser extent than real faces. In the fourth study, we employed functional magnetic resonance imaging to investigate the neural correlates of reflexive social attention. Analyses of the evoked blood-oxygenation level dependent responses pointed to an involvement of striate and extrastriate visual cortices in the encoding of social feature space.
Collectively, these studies help to elucidate under which circumstances social
features are prioritized in a laboratory setting and how this prioritization might be achieved on a neuronal level. The final experimental chapter addresses the question whether these laboratory findings can be generalized to the real world. In this study, participants were introduced to a waiting room scenario in which they interacted with a confederate. Eye movement analyses revealed that gaze behavior heavily depended on the social context and were influenced by whether an interaction is currently desired. We further did not find any evidence for altered gaze behavior in socially anxious participants. Alleged gaze avoidance or hypervigilance in social
anxiety might thus represent a laboratory phenomenon that occurs only under very specific real-life conditions. Altogether the experiments described in the present
thesis thus refine our understanding of social attention and simultaneously
challenge the inferences we can draw from laboratory research.
Hintergrund:
Eine Panikattacke beginnt typischerweise mit der Wahrnehmung einer physiologischen oder psychischen Veränderung, die von der Person als bedrohlich eingestuft wird. Während in klassischen neuroanatomischen Modellen der Panikstörung die Amygdala in der sich anschließenden aufschaukelnden Symptomatik in den Mittelpunkt gestellt wurde, erweitern aktuelle Studien dieses amygdalozentrische Bild und lenken die Aufmerksamkeit auf extratemporale neuronale Netzwerke. Dysfunktionen im neuronalen Aufmerksamkeitsnetzwerk, relevant für die Wahrnehmung und Regulierung exterozeptiver und interozeptiver Prozesse, könnten zur Entstehung einer Panikstörung beitragen. Weiterhin scheinen bestimmte Risikogenotypen für die Panikstörung wie z.B. im Adenosin Rezeptor 2A (ADORA2A) oder dem Neuropeptid S Rezeptor (NPSR1) Gen und die entsprechenden Neurotransmittersysteme in der Regulierung der Aufmerksamkeitsnetzwerke involviert zu sein.
Fragestellung:
Dysfunktionen im noradrenergen bottom-up Alertingnetzwerk und in der dopaminergen exekutiven top-down Aufmerksamkeitskontrolle könnten in einem neurokognitiven Entstehungsmodell der Panikstörung eine wichtige Rolle spielen. Mit Hilfe funktioneller Bildgebung soll die Funktion des neuronalen Aufmerksamkeitsnetzwerkes in einer nichtklinischen Stichprobe abhängig von genetischen Risikofaktoren und einer klinischen Stichprobe von und nach einer kognitiven Verhaltenstherapie untersucht werden.
Methoden:
Im nichtklinischen Teil der Untersuchung wurden in Studie 1 47 gesunde Versuchspersonen für die NPSR1 rs324981 Variante stratifiziert rekrutiert. Mittels fMRT wurde die Aktivität des Alertingnetzwerks und des Executive Control Netzwerks auf neuronaler Ebene mit dem Attentional Networt Test (ANT) untersucht. In Studie 2 wurde bei N=65 Versuchspersonen stratifiziert für die ADORA2A rs5751876 Variante als zusätzliches Verhaltensmaß die Fähigkeit zur interozeptiven Wahrnehmung in Bezug zur Konnektivität im insulären Ruhenetzwerk untersucht. Im klinischen Teil der Untersuchung (Studie 3) wurden 44 Patienten mit Panikstörung sowie eine entsprechend große und gematchte Kontrollgruppe rekrutiert. Es wurden fMRT Ruhemessungen vor und nach Abschluss einer kognitiven Verhaltenstherapie erhoben. Als zusätzliches Verhaltensmaß wurde die selbstberichtete Aufmerksamkeitskontrolle zwischen der Patienten- und der Kontrollgruppe verglichen.
Ergebnisse:
Träger des NPSR1 TT und des ADORA2A TT Risikogenotyps für Angst und Angsterkrankungen zeigten eine erhöhte Aktivität in Teilen des Alertingnetzwerks. Die Aktivität im Executive Control Netzwerk war arealabhängig teilweise erhöht, teilweise reduziert. Innerhalb eines interozeptiven Netzwerks zeigten Träger des ADORA2A TT Genotyps Hinweise auf eine dysfunktionale fronto-striatale-insuläre Interaktion. Im klinischen Teil der Studie zeigten Patienten mit Panikstörung eine reduzierte Konnektivität des dorsolateralen Präfrontalkortex (dlPFC) im fronto-parietalen Aufmerksamkeitsnetzwerk. Die Konnektivität innerhalb dieses Netzwerks korrelierte mit Defiziten in selbstberichteter Aufmerksamkeitskontrolle bei Patienten mit Panikstörung. Nach Abschluss der Therapie zeigte sich bei Patienten, die von der Therapie profitiert hatten, wieder eine Zunahme oder Verbesserung der Konnektivität mit dem dlPFC.
Schlussfolgerung:
Die Ergebnisse dieser Untersuchung betonen die Rolle dysfunktionaler interozeptiver und exterozeptiver Aufmerksamkeitsnetzwerke in der Entstehung von Angsterkrankungen. Bei Patienten mit Panikstörung sowie gesunden Versuchspersonen mit bestimmten prädisponierenden genetischen Variationen scheint eine Dysbalance des neuronalen Aufmerksamkeitsnetzwerks bzgl. der Abstimmung von bottom-up und top-down Netzwerken vorzuliegen.
Extinction is an important mechanism to inhibit initially acquired fear responses. There is growing evidence that the ventromedial prefrontal cortex (vmPFC) inhibits the amygdala and therefore plays an important role in the extinction of delay fear conditioning. To our knowledge, there is no evidence on the role of the prefrontal cortex in the extinction of trace conditioning up to now. Thus, we compared brain structures involved in the extinction of human delay and trace fear conditioning in a between-subjects-design in an fMRI study. Participants were passively guided through a virtual environment during learning and extinction of conditioned fear. Two different lights served as conditioned stimuli (CS); as unconditioned stimulus (US) a mildly painful electric stimulus was delivered. In the delay conditioning group (DCG) the US was administered with offset of one light (CS+), whereas in the trace conditioning group (TCG) the US was presented 4s after CS+ offset. Both groups showed insular and striatal activation during early extinction, but differed in their prefrontal activation. The vmPFC was mainly activated in the DCG, whereas the TCG showed activation of the dorsolateral prefrontal cortex (dlPFC) during extinction. These results point to different extinction processes in delay and trace conditioning. VmPFC activation during extinction of delay conditioning might reflect the inhibition of the fear response. In contrast, dlPFC activation during extinction of trace conditioning may reflect modulation of working memory processes which are involved in bridging the trace interval and hold information in short term memory.
This study investigated the role of bottom-up and top-down neural mechanisms in the processing of emotional face expression during memory formation. Functional brain imaging data was acquired during incidental learning of positive ("happy"), neutral and negative ("angry" or "fearful") faces. Dynamic Causal Modeling (DCM) was applied on the functional magnetic resonance imaging (fMRI) data to characterize effective connectivity within a brain network involving face perception (inferior occipital gyrus and fusiform gyrus) and successful memory formation related areas (hippocampus, superior parietal lobule, amygdala, and orbitofrontal cortex). The bottom-up models assumed processing of emotional face expression along feed forward pathways to the orbitofrontal cortex. The top-down models assumed that the orbitofrontal cortex processed emotional valence and mediated connections to the hippocampus. A subsequent recognition memory test showed an effect of negative emotion on the response bias, but not on memory performance. Our DCM findings showed that the bottom-up model family of effective connectivity best explained the data across all subjects and specified that emotion affected most bottom-up connections to the orbitofrontal cortex, especially from the occipital visual cortex and superior parietal lobule. Of those pathways to the orbitofrontal cortex the connection from the inferior occipital gyrus correlated with memory performance independently of valence. We suggest that bottom-up neural mechanisms support effects of emotional face expression and memory formation in a parallel and partially overlapping fashion.
Numerous studies have shown that humans automatically react with congruent facial reactions, i.e., facial mimicry, when seeing a vis-á-vis’ facial expressions. The current experiment is the first investigating the neuronal structures responsible for differences in the occurrence of such facial mimicry reactions by simultaneously measuring BOLD and facial EMG in an MRI scanner. Therefore, 20 female students viewed emotional facial expressions (happy, sad, and angry) of male and female avatar characters. During picture presentation, the BOLD signal as well as M. zygomaticus major and M. corrugator supercilii activity were recorded simultaneously. Results show prototypical patterns of facial mimicry after correction for MR-related artifacts: enhanced M. zygomaticus major activity in response to happy and enhanced M. corrugator supercilii activity in response to sad and angry expressions. Regression analyses show that these congruent facial reactions correlate significantly with activations in the IFG, SMA, and cerebellum. Stronger zygomaticus reactions to happy faces were further associated to increased activities in the caudate, MTG, and PCC. Corrugator reactions to angry expressions were further correlated with the hippocampus, insula, and STS. Results are discussed in relation to core and extended models of the mirror neuron system (MNS).
Our current environment is characterized by the omnipresence of food cues. The sight and smell of real foods, but also graphically depictions of appetizing foods, can guide our eating behavior, for example, by eliciting food craving and influencing food choice. The relevance of visual food cues on human information processing has been demonstrated by a growing body of studies employing food images across the disciplines of psychology, medicine, and neuroscience. However, currently used food image sets vary considerably across laboratories and image characteristics (contrast, brightness, etc.) and food composition (calories, macronutrients, etc.) are often unspecified. These factors might have contributed to some of the inconsistencies of this research. To remedy this, we developed food-pics, a picture database comprising 568 food images and 315 non-food images along with detailed meta-data. A total of N = 1988 individuals with large variance in age and weight from German speaking countries and North America provided normative ratings of valence, arousal, palatability, desire to eat, recognizability and visual complexity. Furthermore, data on macronutrients (g), energy density (kcal), and physical image characteristics (color composition, contrast, brightness, size, complexity) are provided. The food-pics image database is freely available under the creative commons license with the hope that the set will facilitate standardization and comparability across studies and advance experimental research on the determinants of eating behavior. Read F
Fractal phenomena can be found in numerous scientific areas including neuroscience. Fractals are structures, in which the whole has the same shape as its parts. A specific structure known as pink noise (also called fractal or 1/f noise) is one key fractal manifestation, exhibits both stability and adaptability, and can be addressed via the Hurst exponent (H). FMRI studies using H on regional fMRI time courses used fractality as an important characteristic to unravel neural networks from artificial noise. In this fMRI-study, we examined 103 healthy male students at rest and while performing the 5-choice serial reaction time task. We addressed fractality in a network associated with waiting impulsivity using the adaptive fractal analysis (AFA) approach to determine H. We revealed the fractal nature of the impulsivity network. Furthermore, fractality was influenced by individual impulsivity in terms of decreasing fractality with higher impulsivity in regions of top-down control (left middle frontal gyrus) as well as reward processing (nucleus accumbens and anterior cingulate cortex). We conclude that fractality as determined via H is a promising marker to quantify deviations in network functions at an early stage and, thus, to be able to inform preventive interventions before the manifestation of a disorder.
Emotional-associative learning processes such as fear conditioning and extinction are highly relevant to not only the development and maintenance of anxiety disorders (ADs), but also to their treatment. Extinction, as the laboratory analogue to behavioral exposure, is assumed a core process underlying the treatment of ADs. Although exposure-based treatments are highly effective for the average patient suffering from an AD, there remains a gap in treatment efficacy with over one third of patients failing to achieve clinically significant symptom relief. There is ergo a pressing need for intensified research regarding the underlying neural mechanisms of aberrant emotional-associative learning processes and the neurobiological moderators of treatment (non-)response in ADs.
The current thesis focuses on different applications of the fundamental principles of fear conditioning and extinction by using two example cases of ADs from two different multicenter trials. First, we targeted alterations in fear acquisition, extinction, and its recall as a function of psychopathology in panic disorder (PD) patients compared to healthy subjects using fMRI. Second, exposure-based therapy and pre-treatment patient characteristics exerting a moderating influence on this essential learning process later on (i.e. treatment outcome) were examined using multimodal functional and structural neuroimaging in spider phobia.
We observed aberrations in emotional-associative learning processes in PD patients compared to healthy subjects indicated by an accelerated fear acquisition and an attenuated extinction recall. Furthermore, pre-treatment differences related to defensive, regulatory, attentional, and perceptual processes may exert a moderating influence on treatment outcome to behavioral exposure in spider phobia. Although the current results need further replication, on an integrative meta level, results point to a hyperactive defensive network system and deficient emotion regulation processes (including extinction processes) and top-down control in ADs. This speaks in favor of transdiagnostic deficits in important functional domains in ADs.
Deficits in transdiagnostic domains such as emotion regulation processes could be targeted by enhancing extinction learning or by means of promising tools like neurofeedback. The detection of pre-treatment clinical response moderators, for instance via machine learning frameworks, may help in supporting clinical decision making on individually tailored treatment approaches or, respectively, to avoid ineffective treatment and its related financial costs. In the long run, the identification of neurobiological markers which are capable of detecting non-responders a priori represents an ultimate goal.
Background:
Attention deficit/hyperactivity disorder has been shown to affect working memory, and fMRI studies in children and adolescents with attention deficit/hyperactivity disorder report hypoactivation in task-related attentional networks. However, studies with adult attention deficit/hyperactivity disorder patients addressing this issue as well as the effects of clinically valid methylphenidate treatment are scarce. This study contributes to closing this gap.
Methods:
Thirty-five adult patients were randomized to 6 weeks of double-blind placebo or methylphenidate treatment. Patients completed an fMRI n-back working memory task both before and after the assigned treatment, and matched healthy controls were tested and compared to the untreated patients.
Results:
There were no whole-brain differences between any of the groups. However, when specified regions of interest were investigated, the patient group showed enhanced BOLD responses in dorsal and ventral areas before treatment. This increase was correlated with performance across all participants and with attention deficit/hyperactivity disorder symptoms in the patient group. Furthermore, we found an effect of treatment in the right superior frontal gyrus, with methylphenidate-treated patients exhibiting increased activation, which was absent in the placebo-treated patients.
Conclusions:
Our results indicate distinct activation differences between untreated adult attention deficit/hyperactivity disorder patients and matched healthy controls during a working memory task. These differences might reflect compensatory efforts by the patients, who are performing at the same level as the healthy controls. We furthermore found a positive effect of methylphenidate on the activation of a frontal region of interest. These observations contribute to a more thorough understanding of adult attention deficit/hyperactivity disorder and provide impulses for the evaluation of therapy-related changes.