Belief updating and dopaminergic markers in psychosis

Die Dissertation befasst sich mit Computationalen Mechanismen von Belief-Updating und Neuromelanin als Dopamin-Proxy bei Psychosen. Die Entstehung psychotischer Erfahrungen beruht möglicherweise auf einer veränderten Aktualisierung von Glaubenssätzen (Belief-Updating) durch die unausgewogene Gewichtung der Aktualisierungs-Signale anhand von Unsicherheit. Ziel von Studie 1 war, die verhaltensbezogenen und neuronalen Mechanismen von Belief-Updating bei Schizophrenie und speziell von Wahnvorstellungen zu untersuchen. Menschen mit Wahnvorstellungen zeigten stärkere neuronale Enkodierung der Aktualisierungs-Signale, während diagnostizierte Schizophrenie mit höherer Einschätzung der Umweltvolatilität und geringerer neuronalen Repräsentation derselben einherging. Studie 2 zeigte, dass Menschen mit subklinischen psychoseähnlichen Erfahrungen dazu tendierten, Veränderungspunkten der Umwelt weniger zu berücksichtigen. Ihre Beliefs waren weniger präzise, da sie eine geringere Anzahl voriger Beobachtungen berücksichtigten. Dies spricht für verändertes Belief-Updating als relevanten Mechanismus bei psychotischen Erfahrungen, speziell Wahnvorstellungen, über das Psychosespektrum hinweg ist. Belief-Updating Signale werden über dopaminerge Transmission vermittelt. Quantitative Dopamin-Proxys könnten zukünftig Behandlungsentscheidungen informieren. In Studie 3 führten wir eine Meta-Analyse durch, um die Evidenz für Neuromelanin-sensitive MRT als nicht-invasiven Dopamin-Proxy bei Schizophrenie zu untersuchen. Die Resultate weisen auf eine erhöhte Neuromelaninkonzentration in der Substantia nigra der Schizophreniegruppe hin. Studie 4 untersuchte experimentell die effektive transversale Relaxationsrate (R2*-Kontrast) als Neuromelanin-sensitives MRT-Maß. Es zeigte sich ein erhöhter R2*-Kontrast in der Substantia nigra bei Patient:innen mit Psychose-Spektrum Störungen. Beide Studien liefern Belege für Neuromelanin-sensitive MRT als nicht-invasiven Dopamin-Proxy bei Psychosen.This dissertation is concerned with computational mechanisms of belief updating and neuromelanin as dopamine proxy in psychosis. The formation of psychotic experiences may be rooted in altered belief updating due to misbalanced weighting of belief updating signals according to uncertainty. Study 1 aims to delineate behavioral and neural computational mechanisms of belief updating underlying specifically delusions versus diagnosed schizophrenia. People with delusions showed increased neural updating signals in the caudate and anterior cingulate cortex, while people diagnosed with schizophrenia showed higher estimation of environmental volatility and lower neural representation thereof. Study 2 focuses on behavioral alterations of belief updating in people with subclinical psychotic-like experiences. People with psychotic-like experiences disregarded the probability of environmental change points. Their beliefs were less precise because they took fewer previous observations into account. Both studies support altered belief updating as a relevant mechanism in the formation of psychotic experiences, particularly delusions, across the psychosis spectrum. Belief updating signals are conveyed via dopaminergic transmission, which is a main treatment target of antipsychotic drugs. Quantitative dopamine proxies may inform treatment decisions in clinical settings. In study 3, we conducted a meta-analysis to examine the current evidence for neuromelanin-sensitive MRI as non-invasive dopamine proxy. The results indicate increased neuromelanin concentration in the substantia nigra of patients with schizophrenia. Study 4 experimentally investigated the effective transverse relaxation rate (R2*-contrast) as neuromelanin-sensitive MRI-measure to delineate people with and without psychosis spectrum disorder. The study showed higher R2*-contrast in the substantia nigra in patients. Both studies provide evidence for neuromelanin-sensitive MRI as a non-invasive dopamine proxy in psychosis

The Youth Labour Market in New Zealand - A Comparison to the Pre-Recession Situation

Historically, youth have difficulties in succeeding in the labour market. They can struggle with successfully making the transition from school to work and securing a decent job. The problem of competing and succeeding in the labour market for youth has worsened since the recession in 2008. This paper describes the labour market performance of youth prior to and after the recession. The suite of labour market indicators for youth – including the youth not in employment, education or training (NEET) indicator – derived from the cross-sectional Household Labour Force Survey is used to describe and analyse changes before and after 2008. The description is complemented by highlighting significant risk factors in the youth labour market. The overview of the New Zealand youth labour market together with the odds ratio analysis provides an understanding of the changing labour market situation for youth as well as an insight into which sections of youth particularly struggle in the labour market

Labour Underutilisation in New Zealand

The purpose of this paper is to introduce a preliminary measure of labour underutilisation in New Zealand using data from the Household Labour Force Survey (HLFS). Underutilisation measures add value to the suite of labour market indicators already available from the HLFS. In particular, the underutilisation rate complements the unemployment rate by providing a broader picture of unmet demand for paid employment in New Zealand. The concept of underutilisation and the necessity to measure underutilisation is based on recommendations of an International Labour Organization (ILO) Working Group on Underutilisation made in 2008. The Working Group recommended that ‘... the statistical community should devote serious efforts to introduce, at a par with unemployment, a supplementary concept which measures the employment problem as experienced by individual workers.’ The development of underutilisation measures is also important to mirror changes in increasingly transitional labour markets and to enable analysis and evaluation of these changes

Psychometric Evaluation of the German Version of the Dietary Fat and Free Sugar-Short Questionnaire

Background: The Dietary Fat and free Sugar – Short Questionnaire (DFS) is a cost- and time-efficient self-report screening instrument to estimate dietary intake of saturated fat and free sugar. To date, only the English version has been psychometrically evaluated. We assessed the psychometric characteristics of the German version of the DFS in normal weight, overweight and obese individuals. Method: 65 adult participants completed a German translation of the DFS and a validated food frequency questionnaire (FFQ). We correlated participants’ percentage of energy intake from saturated fat and free sugar from the FFQ with the DFS scores. To establish test-retest reliability, participants completed the DFS a second time. To investigate convergent validity, we correlated participants DFS scores with self-reported eating behaviour and sensitivity to reward. Results: DFS scores correlated with percentage of energy from free sugar (rs = .443) and saturated fatty acids (rs = .258) but not with non-target nutrients. The correlation between DFS scores and percentage energy from free sugar was not moderated by BMI, whereas the correlation with percentage energy from saturated fat slightly decreased with BMI. Intra-class correlation was .801, suggesting excellent test-retest reliability. DFS scores correlated significantly with restraint of eating behaviour (rs = -.380) and feelings of hunger (rs =.275). Correlations of the DFS score with disinhibited eating and sensitivity to reward failed to be significant. Conclusion: Our results suggest that the German version of the DFS provides a reliable and valid estimation for the dietary saturated fat and free sugar intake of normal weight, overweight, and obese individuals.Peer reviewe

Labour Underutilisation in New Zealand

The purpose of this paper is to introduce a preliminary measure of labour underutilisation in New Zealand using data from the Household Labour Force Survey (HLFS). Underutilisation measures add value to the suite of labour market indicators already available from the HLFS. In particular, the underutilisation rate complements the unemployment rate by providing a broader picture of unmet demand for paid employment in New Zealand. The concept of underutilisation and the necessity to measure underutilisation is based on recommendations of an International Labour Organization (ILO) Working Group on Underutilisation made in 2008. The Working Group recommended that ‘... the statistical community should devote serious efforts to introduce, at a par with unemployment, a supplementary concept which measures the employment problem as experienced by individual workers.’ The development of underutilisation measures is also important to mirror changes in increasingly transitional labour markets and to enable analysis and evaluation of these changes

The Youth Labour Market in New Zealand - A Comparison to the Pre-Recession Situation

Historically, youth have difficulties in succeeding in the labour market. They can struggle with successfully making the transition from school to work and securing a decent job. The problem of competing and succeeding in the labour market for youth has worsened since the recession in 2008. This paper describes the labour market performance of youth prior to and after the recession. The suite of labour market indicators for youth – including the youth not in employment, education or training (NEET) indicator – derived from the cross-sectional Household Labour Force Survey is used to describe and analyse changes before and after 2008. The description is complemented by highlighting significant risk factors in the youth labour market. The overview of the New Zealand youth labour market together with the odds ratio analysis provides an understanding of the changing labour market situation for youth as well as an insight into which sections of youth particularly struggle in the labour market

The Potential of Social Media Analytics for Improving Social Media Communication of Emergency Agencies

A growing number of people use social media to seek information or coordinate relief activities in times of crisis. Thus, social media is increasingly used by emergency agencies as well to reach more people in crisis situations. However, the large amount of available data on social media could also be used by emergency agencies to understand how they are perceived by the public and to improve their communication. In this study, we examined the Twitter communication about the German emergency agency “Johanniter-Unfall-Hilfe” by conducting a frequency, sentiment, social network and content analysis. The results revealed that a right-wing political cluster politically instrumentalised an incident related to this agency. Furthermore, some individual persons used social media to express criticism. It can be concluded that the use of social media analytics in the daily work routine of emergency management professionals can be beneficial for improving their social media communication strategy

Neuromelanin-Sensitive Magnetic Resonance Imaging in Schizophrenia: A Meta-Analysis of Case-Control Studies

Background: Psychiatry is in urgent need of reliable biomarkers. Novel neuromelanin-sensitive magnetic resonance imaging (NM-MRI) sequences provide a time-efficient and non-invasive way to investigate the human brain in-vivo. This gives insight into the metabolites of dopaminergic signaling and may provide further evidence for potential dopaminergic alterations in patients with schizophrenia (SCZ). The present systematic review provides a meta-analysis of case-control studies using neuromelanin-sensitive sequences in SCZ vs. healthy controls (HC). Methods: According to predefined search terms and inclusion criteria studies were extracted on PubMed. Meta-analyses with a fixed and random-effects model with inverse variance method, DerSimonian-Laird estimator for tau(2), and Cohen's d were calculated. Bias was assessed using funnel plots. The primary study outcome was contrast-to-noise ratio (CNR) in the substantia nigra compared between HC and SCZ. Results: The total sample of k = 6 studies included n = 183 cases and n = 162 controls. Across all studies we found a significant elevation of CNR in the substantia nigra (d = 0.42 [0.187; 0.655], z = 3.521, p < 0.001) in cases compared to controls. We found no significant difference in the control region of locus coeruleus (d = -0.07 [-0.446; 0.302], z = -0.192, p = 0.847), with CNR for the latter only reported in k = 3 studies. Conclusion: CNR in the substantia nigra were significantly elevated in cases compared to controls. Our results support neuromelanin as a candidate biomarker for dopaminergic dysfunction in schizophrenia. Further studies need to assess this candidate marker in large, longitudinal cohorts and address potential effects of disease state, medication and correlations with symptoms

Structural Differences Between Healthy Subjects and Patients With Schizophrenia or Schizoaffective Disorder: A Graph and Control Theoretical Perspective

The coordinated dynamic interactions of large-scale brain circuits and networks have been associated with cognitive functions and behavior. Recent advances in network neuroscience have suggested that the anatomical organization of such networks puts fundamental constraints on the dynamical landscape of brain activity, i.e., the different states, or patterns of regional activation, and transition between states the brain can display. Specifically, it has been shown that densely connected, central regions control the transition between states that are “easily” reachable (in terms of expended energy), whereas weakly connected areas control transitions to states that are hard-to-reach. Changes in large-scale brain activity have been hypothesized to underlie many neurological and psychiatric disorders. Evidence has emerged that large-scale dysconnectivity might play a crucial role in the pathophysiology of schizophrenia, especially regarding cognitive symptoms. Therefore, an analysis of graph and control theoretic measures of large-scale brain connectivity in patients offers to give insight into the emergence of cognitive disturbances in the disorder. To investigate these potential differences between patients with schizophrenia (SCZ), patients with schizoaffective disorder (SCZaff) and matched healthy controls (HC), we used structural MRI data to assess the microstructural organization of white matter. We first calculate seven graph measures of integration, segregation, centrality and resilience and test for group differences. Second, we extend our analysis beyond these traditional measures and employ a simplified noise-free linear discrete-time and time-invariant network model to calculate two complementary measures of controllability. Average controllability, which identifies brain areas that can guide brain activity into different, easily reachable states with little input energy and modal controllability, which characterizes regions that can push the brain into difficult-to-reach states, i.e., states that require substantial input energy. We identified differences in standard network and controllability measures for both patient groups compared to HCs. We found a strong reduction of betweenness centrality for both patient groups and a strong reduction in average controllability for the SCZ group again in comparison to the HC group. Our findings of network level deficits might help to explain the many cognitive deficits associated with these disorders.Peer reviewe