Why Do Delusions Persist?

Delusions are bizarre and distressing beliefs that characterize certain mental illnesses. They arise without clear reasons and are remarkably persistent. Recent models of delusions, drawing on a neuroscientific understanding of learning, focus on how delusions might emerge from abnormal experience. We believe that these models can be extended to help us understand why delusions persist. We consider prediction error, the mismatch between expectancy and experience, to be central. Surprising events demand a change in our expectancies. This involves making what we have learned labile, updating and binding the memory anew: a process of memory reconsolidation. We argue that, under the influence of excessive prediction error, delusional beliefs are repeatedly reconsolidated, strengthening them so that they persist, apparently impervious to contradiction

Exploring employee engagement with (corporate) social responsibility : a social exchange perspective on organisational participation

Corporate social responsibility (CSR) is a recognised and common part of business activity. Some of the regularly cited motives behind CSR are employee morale, recruitment and retention, with employees acknowledged as a key organisational stakeholder. Despite the significance of employees in relation to CSR, relatively few studies have examined their engagement with CSR and the impediments relevant to this engagement. This exploratory case study-based research addresses this paucity of attention, drawing on one to one interviews and observation in a large UK energy company. A diversity of engagement was found, ranging from employees who exhibited detachment from the CSR activities within the company, to those who were fully engaged with the CSR activities, and to others who were content with their own personal, but not organisational, engagement with CSR. A number of organisational context impediments, including poor communication, a perceived weak and low visibility of CSR culture, and lack of strategic alignment of CSR to business and personal objectives, served to explain this diversity of employee engagement. Social exchange theory is applied to help explore the volition that individual employees have towards their engagement with CSR activities, and to consider the implications of an implicit social, rather than explicit economic, contract between an organisation and its employees in their engagement with CSR

Computational psychiatry: a Rosetta Stone linking the brain to mental illness.

PCF is supported by the Bernard Wolfe Health Neuroscience Fund and the Wellcome Trust. This work was carried out within the Wellcome- and MRC-funded Behavioural and Clinical Neuroscience Institute and the Cambridge and Peterborough NHS Foundation Trust.This is the accepted manuscript. The final version is available from the Lancet Psychiatry at: http://www.thelancet.com/journals/lanpsy/article/PIIS2215-0366%2814%2970298-6/fulltex

Pavlovian conditioning-induced hallucinations result from overweighting of perceptual priors

Some people hear voices that others do not, but only some of those people seek treatment. Using a Pavlovian learning task, we induced conditioned hallucinations in four groups of people who differed orthogonally in their voice-hearing and treatment-seeking statuses. People who hear voices were significantly more susceptible to the effect. Using functional neuroimaging and computational modeling of perception, we identified processes that differentiated voice-hearers from non-voice-hearers and treatment-seekers from non-treatment-seekers and characterized a brain circuit that mediated the conditioned hallucinations. These data demonstrate the profound and sometimes pathological impact of top-down cognitive processes on perception and may represent an objective means to discern people with a need for treatment from those without

Illusions and Delusions: Relating Experimentally-Induced False Memories to Anomalous Experiences and Ideas

The salience hypothesis of psychosis rests on a simple but profound observation that subtle alterations in the way that we perceive and experience stimuli have important consequences for how important these stimuli become for us, how much they draw our attention, how they embed themselves in our memory and, ultimately, how they shape our beliefs. We put forward the idea that a classical memory illusion – the Deese–Roediger–McDermott (DRM) effect – offers a useful way of exploring processes related to such aberrant belief formation. The illusion occurs when, as a consequence of its relationship to previous stimuli, a stimulus that has not previously been presented is falsely remembered. Such illusory familiarity is thought to be generated by the surprising fluency with which the stimulus is processed. In this respect, the illusion relates directly to the salience hypothesis and may share common cognitive underpinnings with aberrations of perception and attribution that are found in psychosis. In this paper, we explore the theoretical importance of this experimentally-induced illusion in relation to the salience model of psychosis. We present data showing that, in healthy volunteers, the illusion relates directly to self reported anomalies of experience and magical thinking. We discuss this finding in terms of the salience hypothesis and of a broader Bayesian framework of perception and cognition which emphasizes the salience both of predictable and unpredictable experiences

Editorial : Predictive mechanisms in action, perception, cognition, and clinical disorders

Acknowledgments The authors would like to acknowledge their funding sources (NIH F32 MH117933 to AD, Alon Fellowship to LR).Peer reviewedPublisher PD

A Computational Account of Borderline Personality Disorder: Impaired Predictive Learning about Self and Others Through Bodily Simulation

Social dysfunction is a prominent and disabling aspect of borderline personality disorder. We reconsider traditional explanations for this problem, especially early disruption in the way an infant feels physical care from its mother, in terms of recent developments in computational psychiatry. In particular, social learning may depend on reinforcement learning though embodied simulations. Such modeling involves calculations based on structures outside the brain such as face and hands, calculations on one\u27s own body that are used to make inferences about others. We discuss ways to test the role of embodied simulation in BPD and potential implications for treatment

Global late Quaternary megafauna extinctions linked to humans, not climate change

The late Quaternary megafauna extinction was a severe global-scale event. Two factors, climate change and modern humans, have received broad support as the primary drivers, but their absolute and relative importance remains controversial. To date, focus has been on the extinction chronology of individual or small groups of species, specific geographical regions or macroscale studies at very coarse geographical and taxonomic resolution, limiting the possibility of adequately testing the proposed hypotheses. We present, to our knowledge, the first global analysis of this extinction based on comprehensive country-level data on the geographical distribution of all large mammal species (more than or equal to 10 kg) that have gone globally or continentally extinct between the beginning of the Last Interglacial at 132 000 years BP and the late Holocene 1000 years BP, testing the relative roles played by glacial–interglacial climate change and humans. We show that the severity of extinction is strongly tied to hominin palaeobiogeography, with at most a weak, Eurasia-specific link to climate change. This first species-level macroscale analysis at relatively high geographical resolution provides strong support for modern humans as the primary driver of the worldwide megafauna losses during the late Quaternary

Effects of methamphetamine administration on information gathering during probabilistic reasoning in healthy humans.

Jumping to conclusions (JTC) during probabilistic reasoning is a cognitive bias repeatedly demonstrated in people with schizophrenia and shown to be associated with delusions. Little is known about the neurochemical basis of probabilistic reasoning. We tested the hypothesis that catecholamines influence data gathering and probabilistic reasoning by administering intravenous methamphetamine, which is known to cause synaptic release of the catecholamines noradrenaline and dopamine, to healthy humans whilst they undertook a probabilistic inference task. Our study used a randomised, double-blind, cross-over design. Seventeen healthy volunteers on three visits were administered either placebo or methamphetamine or methamphetamine preceded by amisulpride. In all three conditions participants performed the "beads" task in which participants decide how much information to gather before making a probabilistic inference, and which measures the cognitive bias towards jumping to conclusions. Psychotic symptoms triggered by methamphetamine were assessed using Comprehensive Assessment of At-Risk Mental States (CAARMS). Methamphetamine induced mild psychotic symptoms, but there was no effect of drug administration on the number of draws to decision (DTD) on the beads task. DTD was a stable trait that was highly correlated within subjects across visits (intra-class correlation coefficients of 0.86 and 0.91 on two versions of the task). The less information was sampled in the placebo condition, the more psychotic-like symptoms the person had after the methamphetamine plus amisulpride condition (p = 0.028). Our results suggest that information gathering during probabilistic reasoning is a stable trait, not easily modified by dopaminergic or noradrenergic modulation.This was supported by a Clinical Scientist Award to Dr. Murray from the Medical Research Council (G0701911); by the University of Cambridge Behavioural and Clinical Neuroscience Institute, funded by a joint award from the Medical Research Council and Wellcome Trust (G1000183 and 093875/Z/10Z); by awards from the Wellcome Trust and the Bernard Wolfe Health Neuroscience Fund to Dr. Fletcher; and by the Wellcome Trust Clinical Research Facility (WTCRF) at Addenbrooke's Hospital. This work was partly conducted at the Clinical Neuroscience Research Unit, Connecticut Mental Health Center. The authors recognize the support of the Connecticut Department of Mental Health and Addiction Services. This publication was also made possible by Clinical and Translational Science Awards grant UL1 RR024139 from the National Center for Research Resources and the National Center for Advancing Translational Science, components of National Institutes of Health, and the NIH Roadmap for Medical Research. Its contents are solely the responsibility of the authors and do not necessarily represent the official view of NIH.This is the final published version, also available from PLOS at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0102683