953 research outputs found
Raman-Spektroskopie für die Echtzeitdetektion von diatomaren Spurengasen
No full textAuthor Severin Hager-Roiser, BScAbweichender Titel laut Übersetzung der Verfasserin/des VerfassersMasterarbeit Johannes Kepler Universität Linz 2025Arbeit gesperr
Stressful Politics? Understanding Politics as a Stress Factor for Mental Health
No full textLife stressors are manifold. They may arise from many different events – e.g. divorce or redundancy – and are established causes of mental health problems. The current project focuses on a specific class of stressors: politics-based stressors. We seek to answer three main questions:
1) How does politics as a source of stress, compared to other non-political stressors, affect citizens’ mental health and well-being?
2) What factors influence individual differences in the impact of politics-based stressors on mental health?
3) What psychological strategies can help reduce the mental health impacts of political stressors?
We answer these questions using online survey data from the UK.
One study (hypotheses cannot be preregistered because the data collection took place in 2023) is based on two waves from Luca Bernardi's "Covid-19 Stressors, Mental Health, and Political Engagement" panel study. The two waves have been fielded in June and July 2023 with YouGov and are based on quota samples of British adults (N~1400). The study has been funded by a Research England Public Policy Support Fund. The study has been designed by Luca Bernardi (University of Liverpool) and James Gross (Stanford University).
A second study will be conducted through Prolific in the context of the UK 2024 General Election. The sample is based on young adults (18-27 years old) (N=1200). The study is based on a two-wave panel survey. The first survey will be fielded right after the elections. A follow-up survey will be fielded six months after. This study has been funded by a UCL Mental Health & Wellbeing Pump-priming Fund. PI: Jonathan Roiser (UCL); Co-Is: Luca Bernardi, Emma Bridger (University of Leicester) and Jack Blumenau (UCL). The study has also been funded by a University of Liverpool Policy Quick Response Fund - Election (PI: Luca Bernardi; Co-Is: Jonathan Rosier, Emma Bridger, Jack Blumenau).
The third study has been funded by the same schemes of the second study, but is based on a daily diary approach, fielded a few days before and after the election (N=200)
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Correction: Measuring cognitive effort without difficulty.
No full textCorrection: Cognitive, Afective, & Behavioral Neuroscience
https://doi.org/10.3758/s13415-023-01065-9
The original article has been updated to include middle initial ‘P’ in co-author’s name Jonathan P. Roiser
Attractor-like dynamics in belief updating in schizophrenia
No full textSubjects with a diagnosis of schizophrenia (Scz) overweight unexpected evidence in probabilistic inference: such evidence becomes 'aberrantly salient'. A neurobiological explanation for this effect is that diminished synaptic gain (e.g. hypofunction of cortical N-methyl-D-aspartate receptors) in Scz destabilizes quasi-stable neuronal network states (or 'attractors'). This attractor instability account predicts that i) Scz would overweight unexpected evidence but underweight consistent evidence, ii) belief updating would be more vulnerable to stochastic fluctuations in neural activity, and iii) these effects would correlate.Hierarchical Bayesian belief updating models were tested in two independent datasets (n=80 and n=167, male and female) comprising human subjects with schizophrenia, and both clinical and non-clinical controls (some tested when unwell and on recovery) performing the 'probability estimates' version of the beads task (a probabilistic inference task). Models with a standard learning rate, or including a parameter increasing updating to 'disconfirmatory evidence', or a parameter encoding belief instability were formally compared.The 'belief instability' model (based on the principles of attractor dynamics) had most evidence in all groups in both datasets. Two of four parameters differed between Scz and non-clinical controls in each dataset: belief instability and response stochasticity. These parameters correlated in both datasets. Furthermore, the clinical controls showed similar parameter distributions to Scz when unwell, but were no different to controls once recovered.These findings are consistent with the hypothesis that attractor network instability contributes to belief updating abnormalities in Scz, and suggest that similar changes may exist during acute illness in other psychiatric conditions.SIGNIFICANCE STATEMENTSubjects with a diagnosis of schizophrenia (Scz) make large adjustments to their beliefs following unexpected evidence, but also smaller adjustments than controls following consistent evidence. This has previously been construed as a bias towards 'disconfirmatory' information, but a more mechanistic explanation may be that in Scz, neural firing patterns ('attractor states') are less stable and hence easily altered in response to both new evidence and stochastic neural firing. We model belief updating in Scz and controls in two independent datasets using a hierarchical Bayesian model, and show that all subjects are best fit by a model containing a belief instability parameter. Both this and a response stochasticity parameter are consistently altered in Scz, as the unstable attractor hypothesis predicts
The cognitive and neural mechanisms of depression in Parkinson's disease
No full textDepression in Parkinson’s disease (PD) is common, disabling and has poor outcomes. Dopamine has a well-established role in both reward and motivational pathways. The cardinal symptoms of PD are caused by dopaminergic neurodegeneration and consequently PD is a model of striatal and dopamine dysfunction. This thesis aims to investigate the neural and cognitive mechanisms underlying depression in PD and the role of dopamine in its aetiology and treatment. Following the general introduction, the first empirical chapter is a systematic review and meta-analysis of reward processing in PD and its relationship with dopamine state and neuropsychiatric syndromes. The analysis revealed that reward processing is impaired in PD, but this disruption varies depending on the specific cognitive subcomponent and dopamine state. The second empirical chapter investigated how progressive neurodegeneration of dopaminergic projections to the striatum over time in PD was associated with motivational symptoms of depression. I found that motivational symptoms emerge as the disease progresses, after a threshold level of dopaminergic neurodegeneration is reached. The third empirical chapter explored whether there are dissociable effects of dopaminergic medications on different depression symptom dimensions in PD. I found that treatment with dopamine agonists appears to specifically reduce motivational symptoms over time, whereas monoamine oxidase-B inhibitors may improve both depressive and motivation symptoms, albeit the latter effect is attenuated in patients with more severe dopaminergic neurodegeneration. Our willingness to exert effort for a given goal is dependent on the magnitude of the potential reward of an action. This process, termed effort-based decision making, is an essential component of motivation. In the final empirical chapter, I investigated whether dopamine-dependent disruption of effort-based decision-making is a mechanism driving depression in PD. I found that depression in PD is associated with lower sensitivity to rewards, which remains unresponsive to dopaminergic medication. In contrast, dopamine treatment improves reward sensitivity in non-depressed PD. Taken together, the studies in this thesis add new insights into the key cognitive and neural mechanisms underlying depression in PD. My final experiment identified reward sensitivity as a potential novel treatment target for PD depression that may require non-dopaminergic therapies
Constructing the Self in Adolescence: Learning What We Like and What We're Like
No full textSelf-concept refers to beliefs about our own abilities, traits, and preferences, and how we perceive ourselves in relation to others. The quality and valence of these beliefs can have significant impacts on mental health. In this thesis, I investigate the motivations and cognitive abilities that underlie the formation of self-referential beliefs during adolescence. Adolescence is a critical period for self-concept construction as adolescents gain independence and navigate new environments. In the first experiment, I demonstrate that the ability to reflect upon our own decisions shows age-related improvement during early adolescence. I present evidence that the development of this metacognition may encourage independent decision making during adolescence. I then investigate how adolescents form judgements of their own traits, finding that preferential memory for self-judged versus other-judged traits is heightened in early adolescence and declines across the teenage years and into adulthood. I also demonstrate that negative self-judgements show a quadratic association with age, peaking around age 19, and that preferential memory for positive over negative traits increases across adolescence. In the third experiment, I examine how adolescents can use the process of choosing itself to gain certainty over their own preferences. I show that the use of choice for value refinement increases across early adolescence and is associated with depressive symptoms. In the final experiment, I utilise geolocation tracking and ecological momentary assessment to explore the impact of independent decision making and exploration on affect and social network growth. I also explore how adolescents form judgements of and adjust their behaviour to changing social norms, a potentially important source of information for adolescent self-concept development. I argue that by understanding the factors that contribute to the formation of the self-concept during this critical developmental period, we can better support young people in developing a positive self-concept and promoting mental health
Locus coeruleus signal intensity and emotion regulation in agitation in Alzheimer’s disease
No full textAbstract Hyperphosphorylated tau accumulation is seen in the noradrenergic locus coeruleus from the earliest stages of Alzheimer’s disease onwards and has been associated with symptoms of agitation. It is hypothesized that compensatory locus coeruleus-noradrenaline system overactivity and impaired emotion regulation could underlie agitation propensity, but to our knowledge this has not previously been investigated. A better understanding of the neurobiological underpinnings of agitation would help the development of targeted prevention and treatment strategies. Using a sample of individuals with amnestic mild cognitive impairment and probable mild Alzheimer’s disease dementia from the German Center for Neurodegenerative Diseases (DZNE)-Longitudinal Cognitive Impairment and Dementia (DELCODE) study cohort (N = 309, aged 67–96 years, 51% female), we assessed cross-sectional relationships between a latent factor representing the functional integrity of an affect-related executive regulation network and agitation point prevalence and severity scores. In a subsample of individuals with locus coeruleus MRI imaging data (N = 37, aged 68–93 years, 49% female), we also investigated preliminary associations between locus coeruleus MRI contrast ratios (a measure of structural integrity, whole or divided into rostral, middle, and caudal thirds) and individual affect-related regulation network factor scores and agitation measures. Regression models controlled for effects of age and clinical disease severity and, for models including resting-state functional MRI connectivity variables, grey matter volume and education years. Agitation point prevalence showed a positive relationship with a latent factor representing the functional integrity (and a negative relationship with a corresponding structural measure) of the affect-related executive regulation network. Locus coeruleus MRI contrast ratios were positively associated with agitation severity (but only for the rostral third, in N = 13) and negatively associated with the functional affect-related executive regulation latent factor scores. Resting-state functional connectivity between a medial prefrontal cortex region and the left amygdala was related to locus coeruleus MRI contrast ratios. These findings implicate the involvement of locus coeruleus integrity and emotion dysregulation in agitation in Alzheimer’s disease and support the presence of potential compensatory processes. At the neural level, there may be a dissociation between mechanisms underlying agitation risk per se and symptom severity. Further studies are needed to replicate and extend these findings, incorporating longitudinal designs, measures of autonomic function and non-linear modelling approaches to explore potential causal and context-dependent relationships across Alzheimer’s disease stages
Anhedonia is associated with blunted reward sensitivity in first-degree relatives of patients with major depression
No full textBACKGROUND: Anhedonia is a cardinal feature of major depression and is hypothesized to be driven by low motivation, in particular blunted reward sensitivity. It has been suggested to be a marker that represents a genetic predisposition to this disorder. However, little is known about the mechanisms underlying this heightened risk in unaffected first-degree relatives of patients with major depression. We previously demonstrated abnormal reward biases in acutely depressed patients. The present study aimed to examine the development of reward bias in first-degree relatives of patients with major depression. METHODS: Forty-seven first-degree relatives of patients with major depression (26 females, age 18-52) and 60 healthy controls with no family history of depression (34 females, age 21-48) were recruited. A probabilistically rewarded difficult visual discrimination task, in which participants were instructed about the contingencies, was used to assess blunted reward sensitivity. A response bias towards the more frequently rewarded stimulus (termed "reward bias") was the primary outcome variable in this study. Participants also completed self-reported measures of anhedonia and depressive symptoms. RESULTS: Compared with the control group, relatives of patients with major depression with sub-clinical depressive symptoms displayed a blunted reward bias. Relatives without symptoms displayed largely intact motivational processing on both self-report and experimental measures. The degree of anhedonia was associated with attenuated reward bias in first-degree relatives of patients with major depression, especially in those with sub-clinical symptoms. LIMITATIONS: The study did not include a depressed patient group, which restricted our ability to interpret the observed group differences. CONCLUSIONS: Blunted reward sensitivity may be largely manifested in a subgroup of relatives with high levels of depressive symptoms
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