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For 3000 years, psychedelics have been used in religious contexts to enhance spiritual thinking, well-being, and a sense of community. In the last few years, a renaissance in the use of psychedelic drugs for mental disorders has occurred in Western society; consequently, a pressing scientific need to elucidate the intricate mechanisms underlying their actions has arisen. Psychedelics mainly bind to serotonin (5-HT) receptors, particularly [5-HT.sub.2A] receptors, but may also bind to other receptors. Unlike conventional psychotropic drugs used in psychiatry, psychedelics introduce a distinctive complexity. They not only engage in receptor activation, but also exert influence over specific neural circuits, thereby facilitating transformative cognitive experiences and fostering what many have identified as a spiritual contemplation or mystical experience. This comprehensive review describes clinical studies that have examined the propensity of psychedelics to enhance spiritual, mystical, and transcendent cognitive states. This multifaceted nature, encompassing diverse components and paradigms, necessitates careful consideration during the investigation of psychedelic mechanisms of action to avoid oversimplification. The present review endeavours to elucidate the mechanisms underlying the actions of 2 principal psychedelic substances, psilocybin and lysergic acid diethylamide (LSD), with a focus on monoamine and glutamate receptor mechanisms; molecular aspects, such as neuroplasticity and epigenetics; as well as the impact of psychedelics on brain circuits, including the default mode network and the cortico-striato-thalamo-cortical network. Given their distinctive and intricate mechanisms of action, psychedelics necessitate a novel conceptual framework in psychiatry, offering insight into the treatment of mental health disorders and facilitating the integration of the realms of brain, mind, and spirituality., Introduction Psychedelics have been used in religious ceremonies by various cultures throughout history. These substances, known for their ability to induce altered states of consciousness, have been employed as sacraments, [...]

Ambiguity tolerance (AT) is the way one perceives and processes ambiguous environmental stimulus information. By using resting-state functional magnetic resonance imaging (fMRI) and the Multiple Stimulus Types Ambiguity Tolerance Scale-II (MSTAT-II), the present study investigated the association between AT and functional connectivity of the brain in 315 healthy young participants. Based on previous studies, the middle temporal gyrus (MTG), inferior parietal lobe (IPL), orbitofrontal gyrus (OFC), middle frontal gyrus (MFG), anterior insula (AI), anterior cingulate cortex (ACC) and amygdala were selected as the seed regions. We investigated the association between whole-brain functional connectivity and AT scores. The results showed a significant positive correlation between the AT scores and functional connectivity between the left IPL and middle cingulate cortex (MCC), left MFG, and left MTG, reflecting the neural basis of AT, which represents how people perceive ambiguous stimuli and assess possible risks underlying ambiguity. And the OFC was found a negative correlation between the AT scores and functional connectivity between the ACC, which revealed the underlying mechanism of ambiguity intolerance., Author(s): Di Liu [sup.1] , Jiangzhou Sun [sup.2] [sup.3] , Zhiting Ren [sup.2] [sup.3] , Jiahui Yang [sup.1] , Baoguo Shi [sup.1] , Jiang Qiu [sup.2] [sup.3] Author Affiliations: (1) [...]

Background: Investigating adolescents and young adults may provide a unique opportunity to understand developmental aspects of the neurobiology of depression. During adolescence, a considerable physiologic reorganization of both grey and white matter of the brain takes place, and it has been suggested that differences in grey-matter volumes during adolescence may reflect different maturational processes. Methods: We investigated grey-matter volumes in a comparatively large sample (n = 103) of adolescents and young adults (aged 12 to 27 years), 60 of them with a diagnosis of current depression. Results: Replicating previous studies, we found a clear whole-brain effect of age: the older the participants, the lower their global grey-matter volumes, particularly in the paracingulate and prefrontal cortices. Contrasting depressed and healthy youth in a whole-brain approach, we found greater grey-matter volumes in the dorsolateral prefrontal cortex of those with depression. Furthermore, a region-of-interest analysis indicated lower grey-matter volumes in the hippocampus in participants with depression compared with healthy controls. Limitations: The present study was limited because of a skewed sex distribution, its cross-sectional design and the fact that some participants were taking an antidepressant. Conclusion: During adolescence, restructuring of the brain is characterized by marked decreases in prefrontal grey-matter volumes, interpreted as a correlate of brain maturation. Findings of greater volumes in the prefrontal cortex, particularly in younger adolescents with depression, may suggest that these participants were more prone to delayed brain maturation or increased neuroplasticity. This finding may represent a risk factor for depression or constitute an effect of developing depression., Introduction Current research has provided evidence for neurobiological correlates of depression in terms of brain function and structure. Typical findings involve reduced hippocampal volumes and lower grey-matter volumes in cortical [...]

A persistent debate in behavioral research is whether brain size or architecture relates to cognitive performance. A growing body of evidence has demonstrated correlations between brain size and ecological and behavioral tasks. These studies are premised on a causal link between brain size and cognitive function, although this association has little empirical backing. We show, for a set of 46 species from 17 primate genera, that competence on a series of eight executive function cognitive tasks both correlate across tasks and with brain size and architecture across species. Our model selection approach showed that, although several measures of brain component volumes are significantly associated with performance, hippocampus size is the best predictor of overall performance. The best performing model also includes total brain size and relative neocortex size. Additionally, absolute measures are much more predictive of performance than relative measures of brain and brain component size. These results are consistent with the hippocampus' role in learning, and the executive brain (neocortex) being important for problem solving and consolidation. Our findings challenge and extend those of previous analyses by clarifying the relationship between overall brain size and specific regional volumes. They also suggest that commonly used indices of encephalization, such as residuals of brain volume regressed on body size, may confound rather than clarify matters. Keywords: executive function, primates, brain volume, cognitive ability Supplemental materials: http://dx.doi.org/10.1037/a0018894.supp DOI: 10.1037/a0018894