Active inference, evidence accumulation, and the urn task

Deciding how much evidence to accumulate before making a decision is a problem we and other animals often face, but one that is not completely understood. This issue is particularly important because a tendency to sample less information (often known as reflection impulsivity) is a feature in several psychopathologies, such as psychosis. A formal understanding of information sampling may therefore clarify the computational anatomy of psychopathology. In this theoretical letter, we consider evidence accumulation in terms of active (Bayesian) inference using a generic model of Markov decision processes. Here, agents are equipped with beliefs about their own behavior--in this case, that they will make informed decisions. Normative decision making is then modeled using variational Bayes to minimize surprise about choice outcomes. Under this scheme, different facets of belief updating map naturally onto the functional anatomy of the brain (at least at a heuristic level). Of particular interest is the key role played by the expected precision of beliefs about control, which we have previously suggested may be encoded by dopaminergic neurons in the midbrain. We show that manipulating expected precision strongly affects how much information an agent characteristically samples, and thus provides a possible link between impulsivity and dopaminergic dysfunction. Our study therefore represents a step toward understanding evidence accumulation in terms of neurobiologically plausible Bayesian inference and may cast light on why this process is disordered in psychopathology

Longitudinal Monitoring of SARS-CoV-2 IgM and IgG Seropositivity to Detect COVID-19.

BackgroundSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a novel beta-coronavirus that has recently emerged as the cause of the 2019 coronavirus pandemic (COVID-19). Polymerase chain reaction (PCR) based tests are optimal and recommended for the diagnosis of an acute SARS-CoV-2 infection. Serology tests for viral antibodies provide an important tool to diagnose previous exposure to the virus. Here we evaluate the analytical performance parameters of the Diazyme SARS-CoV-2 IgM/IgG serology assays and describe the kinetics of IgM and IgG seroconversion observed in patients with PCR-confirmed COVID-19 who were admitted to our hospital.MethodsWe validated the performance of the Diazyme assay in 235 presumed SARS-CoV-2 negative subjects to determine specificity. Subsequently, we evaluated the SARS-CoV-2 IgM and IgG seroconversion of 54 PCR-confirmed COVID-19 patients and determined sensitivity of the assay at three different timeframes.ResultSensitivity and specificity for detecting seropositivity at ≥15 days following a positive SARS-CoV-2 PCR result, was 100.0% and 98.7% when assaying for the panel of IgM and IgG. The median time to seropositivity observed for a reactive IgM and IgG result from the date of a positive PCR was 5 days (IQR: 2.75-9 days) and 4 days (IQR: 2.75-6.75 days), respectively.ConclusionsOur data demonstrate that the Diazyme IgM/IgG assays are suited for the purpose of detecting SARS-CoV-2 IgG and IgM in patients with suspected SARS-CoV-2 infections. For the first time, we report longitudinal data showing the evolution of seroconversion for both IgG and IgM in a cohort of acutely ill patients in the United States. We also demonstrate a low false positive rate in patients who were presumed to be disease free

Bostonia

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Rapid convergence of time-averaged frequency in phase synchronized systems

Numerical and experimental evidence is presented to show that many phase synchronized systems of non-identical chaotic oscillators, where the chaotic state is reached through a period-doubling cascade, show rapid convergence of the time-averaged frequency. The speed of convergence toward the natural frequency scales as the inverse of the measurement period. The results also suggest an explanation for why such chaotic oscillators can be phase synchronized.Comment: 6 pages, 9 figure

Dopaminergic basis for signalling belief updates, but not surprise, and the link to paranoia

Distinguishing between meaningful and meaningless sensory information is fundamental to forming accurate representations of the world. Dopamine is thought to play a central role in processing the meaningful information content of observations, which motivates an agent to update their beliefs about the environment. However, direct evidence for dopamine’s role in human belief updating is lacking. We addressed this question in healthy volunteers who performed a model-based functional magnetic resonance imaging (fMRI) task designed to separate the neural processing of meaningful and meaningless sensory information. We modelled participant behaviour using a normative Bayesian observer model, and used the magnitude of the model-derived belief update following an observation to quantify its meaningful information content. We also acquired positron emission tomography (PET) imaging measures of dopamine function in the same subjects. We show that the magnitude of belief updates about task structure (meaningful information), but not pure sensory surprise (meaningless information), are encoded in midbrain and ventral striatum activity. Using PET we show that the neural encoding of meaningful information is negatively related to dopamine-2/3 receptor availability in the midbrain and dexamphetamine-induced dopamine release capacity in the striatum. Trial-by-trial analysis of task performance indicated that subclinical paranoid ideation is negatively related to behavioural sensitivity to observations carrying meaningful information about the task structure. The findings provide direct evidence implicating dopamine in model-based belief updating in humans, and have implications for understating the pathophysiology of psychotic disorders where dopamine function is disrupted

Incorporating Sociocultural Phenomena into Ecosystem-Service Valuation: The Importance of Critical Pluralism

Ecosystem-services scholarship has largely focused on monetary valuation and the material contributions of ecosystems to human well-being. Increasingly, research is calling for a deeper understanding of how less tangible, nonmaterial values shape management and stakeholder decisions. We propose a framework that characterizes a suite of sociocultural phenomena rooted in key social science disciplines that are currently underrepresented in the ecosystem-services literature. The results from three example studies are presented to demonstrate how the tenets of this conceptual model can be applied in practice. We consider the findings from these studies in light of three priorities for future research: (1) complexities in individual and social functioning, (2) the salience and specificity of the perceived benefits of nature, and (3) distinctions among value concepts. We also pose a series of questions to stimulate reflection on how ecosystem-services research can adopt more pluralistic viewpoints that accommodate different forms of knowledge and its acquisition

Precision and neuronal dynamics in the human posterior parietal cortex during evidence accumulation

Primate studies show slow ramping activity in posterior parietal cortex (PPC) neurons during perceptual decision-making. These findings have inspired a rich theoretical literature to account for this activity. These accounts are largely unrelated to Bayesian theories of perception and predictive coding, a related formulation of perceptual inference in the cortical hierarchy. Here, we tested a key prediction of such hierarchical inference, namely that the estimated precision (reliability) of information ascending the cortical hierarchy plays a key role in determining both the speed of decision-making and the rate of increase of PPC activity. Using dynamic causal modelling of magnetoencephalographic (MEG) evoked responses, recorded during a simple perceptual decision-making task, we recover ramping-activity from an anatomically and functionally plausible network of regions, including early visual cortex, the middle temporal area (MT) and PPC. Precision, as reflected by the gain on pyramidal cell activity, was strongly correlated with both the speed of decision making and the slope of PPC ramping activity. Our findings indicate that the dynamics of neuronal activity in the human PPC during perceptual decision-making recapitulate those observed in the macaque, and in so doing we link observations from primate electrophysiology and human choice behaviour. Moreover, the synaptic gain control modulating these dynamics is consistent with predictive coding formulations of evidence accumulation

Kedudukan Anak Akibat Batalnya Perkawinan Karena Hubungan Darah Menurut Hukum Positif

Penelitian ini dilakukan dengan tujuan untuk mengetahui bagaimana pengaturan hukum tentang Pembatalan Perkawinan karena hubungan darah menurut Hukum Positif Di Indonesia dan bagaimana kedudukan hukum anak yang lahir setelah pembatalan perkawinan menurut Hukum Positif di Indonesia. Dengan menggunakan metode penelitian yuridis normatif, maka dapat disimpulkan: 1. Pengaturan hukum mengenai pembatalan perkawinan di Indonesia masih beragam walaupun Undang-Undang perkawinan yaitu Undang-Undang Nomor 1 Tahun 1974 seringkali disebut unifikasi hukum perkawinan. Pembatalan perkawinan merupakan putusnya perkawinan disebabkan persyaratan perkawinan yang diatur dalam undang-undang dan larangan perkawinan tidak dipenuhi. 2. Status hukum anak yang lahir dalam perkawinan yang telah batal pada dasarnya merupakan anak yang sah sebagaimana diatur dalam Undang-Undang Nomor 1 Tahun 1974 dalam Pasal 28. Berdasarkan Putusan Mahkamah Konstitusi Nomor 46/PUU-VIII/2010 Tentang Pengujian pasal 2 ayat 2 dan pasal 43 ayat 1 Undang-Undang Perkawinan yaitu Undang-Undang Nomor 1 Tahun 1974 yang menyatakan bahwa pasal 43 ayat Undang-Undang Nomor 1 Tahun 1974 melanggar Undang-Undang Dasar Republik Indonesia pasal 28 B ayat 1 dan 2 dan pasal 28 D ayat 1

Evaluating Disparities in Proton Radiation Therapy Use in AHOD1331, a Contemporary Children\u27s Oncology Group Trial for Advanced-Stage Hodgkin Lymphoma

The indications for proton radiation therapy carry the strongest evidence in pediatric cancers. In a recently published letter, Bitterman et al reviewed factors associated with receipt of proton radiation therapy in patients enrolled in Children\u27s Oncology Group (COG) solid tumor and CNS tumor trials. They demonstrated that Black children were less likely to receive this treatment than non-Hispanic white patients, a disparity that persisted when controlling for other demographic and clinical variables. We strongly commend them for their work, as addressing racism and infrastructural barriers to care requires its identification