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Objective: Social media facilitate the distribution of conspiracy theories. It is uncertain whether indeed the number of myths and also the number of those who appropriate myths has increased. Conspiracy theories have so far essentially been the subject of sociological and psychosociological research showing a general disposition to become infected irrespective of the topic of a myth. Are there specific psychopathological risk factors for becoming infected by conspiracy myths? Are there effective therapeutic or preventive measures?, Methods: A systematic search was carried out in PubMed using the query "conspir*[title] AND review" followed by manual selection and appraisal only of publications addressing conspiracy theories in general, i.e. not limited to specific myths, with a focus on systematic reviews and meta-analyses. Moreover, the publications identified were manually screened for further meta-analyses., Results: The search resulted in 166 hits. The available evidence is essentially based on studies using questionnaires, which can clarify only associations but not causalities. The evidence suggests that the strongest correlates of conspiratorial ideation pertain to low cognitive abilities, nonanalytic style of thought resulting in reduced balancing of probabilities before deciding, feelings of loss of control, paranoia, schizotypy and the dark triad (narcissism, Machiavellianism, authoritarianism)., Conclusion: Specific psychological characteristics are risk factors for conspiratorial ideation. Current research approaches are unsuitable to clarify whether psychiatric disorders are overrepresented. Sociodemographic risk factors include male gender, low level of education, low income, social isolation and are non-specific. Group processes promote, again presumably nonspecifically, conspiracy theories thus contributing to social polarization. The genetic basis and neurobiological mechanisms are unknown. Conspiracy theories were and are used as an instrument of political contention. The enlightened democratic social contract requires free, unbiased thinking. Consequently, the risk factors identified so far facilitate conspiratorial ideation and question the very fundaments of the social contract by impairing unbiased evaluation and decision making. Therefore, prevention is warranted. ., (© 2024. The Author(s), under exclusive licence to Springer Medizin Verlag GmbH, ein Teil von Springer Nature.)

In the adult murine brain, neural stem cells (NSCs) can be found in two main niches: the dentate gyrus (DG) and the subventricular zone (SVZ). In the DG, NSCs produce intermediate progenitors (IPs) that differentiate into excitatory neurons, while progenitors in the SVZ migrate to the olfactory bulb (OB), where they mainly differentiate into inhibitory interneurons. Neurogenesis, the process of generating new neurons, persists throughout life but decreases dramatically with aging, concomitantly with increased inflammation. Although many cell types, including microglia, undergo significant transcriptional changes, few such changes have been detected in neural progenitors. Furthermore, transcriptional profiles in progenitors from different neurogenic regions have not been compared on a single-cell level, and little is known about how they are affected by aging-related inflammation. We have generated a single cell RNA sequencing dataset enriched for IPs, which revealed that most aged neural progenitors only acquire minor transcriptional changes. However, progenitors set to become excitatory neurons decrease faster than others. In addition, a population in the aged SVZ, not detected in the OB, acquired major transcriptional activation related to immune responses. This suggests that differences in age related neurogenic decline between regions is not due to tissue differences but rather cell type specific intrinsic transcriptional programs, and that subset of neuroblasts in the SVZ react strongly to age related inflammatory cues., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Fritze, Lang, Sommarin, Soneji and Ahlenius.)

Adult neurogenesis continues throughout life but declines dramatically with age and in neurodegenerative disorders such as Alzheimer's disease. In parallel, microglia become activated resulting in chronic inflammation in the aged brain. A unique type of microglia, suggested to support neurogenesis, exists in the subventricular zone (SVZ), but little is known how they are affected by aging. We analyzed the transcriptome of aging microglia and identified a unique neuroprotective activation profile in aged SVZ microglia, which is partly shared with disease-associated microglia (DAM). CX3C motif chemokine receptor 1 (CX3CR1) is characteristically expressed by brain microglia where it directs migration to targets for phagocytosis. We show that Cx3cr1 expression, as in DAM, is downregulated in old SVZ microglia and that heterozygous Cx3cr1 mice have increased proliferation and neuroblast number in the aged SVZ but not in the dentate gyrus, identifying CX3CR1 signaling as a novel age and brain region-specific regulator of neurogenesis., (© 2024 The Authors. Developmental Neurobiology published by Wiley Periodicals LLC.)