Confidence and psychosis: a neuro-computational account of contingency learning disruption by NMDA blockade.

A state of pathological uncertainty about environmental regularities might represent a key step in the pathway to psychotic illness. Early psychosis can be investigated in healthy volunteers under ketamine, an NMDA receptor antagonist. Here, we explored the effects of ketamine on contingency learning using a placebo-controlled, double-blind, crossover design. During functional magnetic resonance imaging, participants performed an instrumental learning task, in which cue-outcome contingencies were probabilistic and reversed between blocks. Bayesian model comparison indicated that in such an unstable environment, reinforcement learning parameters are downregulated depending on confidence level, an adaptive mechanism that was specifically disrupted by ketamine administration. Drug effects were underpinned by altered neural activity in a fronto-parietal network, which reflected the confidence-based shift to exploitation of learned contingencies. Our findings suggest that an early characteristic of psychosis lies in a persistent doubt that undermines the stabilization of behavioral policy resulting in a failure to exploit regularities in the environment.FV was supported by the Groupe Pasteur Mutualité. RG was supported by the Fondation pour la Recherche Médicale and the Fondation Bettencourt Schueller. SP is supported by a Marie Curie Intra-European fellowship (FP7-PEOPLE-2012-IEF). AF was supported by National Health and Medical Research Council grants (IDs : 1050504 and 1066779) and an Australian Research Council Future Fellowship (ID: FT130100589). This work was supported by the Wellcome Trust and the Bernard Wolfe Health Neuroscience Fund.This is the final version of the article. It first appeared from the Nature Publishing Group via http://dx.doi.org/10.1038/mp.2015.7

Timbre from Sound Synthesis and High-level Control Perspectives

International audienceExploring the many surprising facets of timbre through sound manipulations has been a common practice among composers and instrument makers of all times. The digital era radically changed the approach to sounds thanks to the unlimited possibilities offered by computers that made it possible to investigate sounds without physical constraints. In this chapter we describe investigations on timbre based on the analysis by synthesis approach that consists in using digital synthesis algorithms to reproduce sounds and further modify the parameters of the algorithms to investigate their perceptual relevance. In the first part of the chapter timbre is investigated in a musical context. An examination of the sound quality of different wood species for xylophone making is first presented. Then the influence of instrumental control on timbre is described in the case of clarinet and cello performances. In the second part of the chapter, we mainly focus on the identification of sound morphologies, so called invariant sound structures responsible for the evocations induced by environmental sounds by relating basic signal descriptors and timbre descriptors to evocations in the case of car door noises, motor noises, solid objects, and their interactions

The Virtual Teacher (VT) Paradigm: Learning New Patterns of Interpersonal Coordination Using the Human Dynamic Clamp

The Virtual Teacher paradigm, a version of the Human Dynamic Clamp (HDC), is introduced into studies of learning patterns of inter-personal coordination. Combining mathematical modeling and experimentation, we investigate how the HDC may be used as a Virtual Teacher (VT) to help humans co-produce and internalize new inter-personal coordination pattern(s). Human learners produced rhythmic finger movements whilst observing a computer-driven avatar, animated by dynamic equations stemming from the well-established Haken-Kelso-Bunz (1985) and Schöner-Kelso (1988) models of coordination. We demonstrate that the VT is successful in shifting the pattern co-produced by the VT-human system toward any value (Experiment 1) and that the VT can help humans learn unstable relative phasing patterns (Experiment 2). Using transfer entropy, we find that information flow from one partner to the other increases when VT-human coordination loses stability. This suggests that variable joint performance may actually facilitate interaction, and in the long run learning. VT appears to be a promising tool for exploring basic learning processes involved in social interaction, unraveling the dynamics of information flow between interacting partners, and providing possible rehabilitation opportunities

Positron emission tomography in patients with psychogenic non-epileptic seizures

Aileen McGonigal,1–3 Marie Arthuis,3 Jean-Arthur Micoulaud-Franchi,4,5 Fabrice Bartolomei,1–3 Eric Guedj6–8 1Institut de Neurosciences des Systèmes, INSERM UMR 1106, Marseille, France; 2Aix Marseille University, Faculty of Medicine, Marseille, France; 3Clinical Neurophysiology Department, Timone Hospital, Marseille, France; 4Department of Functional Investigation of the Nervous System, Sleep Clinic, Bordeaux University Hospital, Bordeaux, France; 5USR CNRS 3413, University of Bordeaux, France; 6Biophysics and Nuclear Medicine Department, Timone Hospital, Marseille, France; 7Aix-Marseille University, CERIMED, Marseille, France; 8Aix-Marseille University, CNRS, UMR7289, INT, Marseille, FranceWe have read with interest the recent review entitled “Uncovering the etiology of conversion disorder: insights from functional neuroimaging” by Maryam Ejareh dar and Richard AA Kanaan,1 published in Neuropsychiatric Disease and Treatment. Our paper on resting state brain metabolism measured by positron emission tomography (PET) was included and discussed.2 We were most surprised to see that the authors of the review seem to have misunderstood the findings of our study, which concerned patients with psychogenic non-epileptic seizures (PNES). The authors state that the 16 patients included in our study “were later found to have PNES with comorbid epilepsy”. This is incorrect, since our study included only patients with PNES in whom comorbid epilepsy was excluded. This crucial point is indeed detailed in the Methods section of our article and clearly stated in the abstract: “in all patients, the diagnosis was subsequently confirmed to be PNES with no coexisting epilepsy.” It is thus on the basis of incorrect understanding of our results that Drs Ejareh dar and Kanaan discuss the possible significance of hypometabolism in the anterior cingulate region described in our paper, and erroneously suggest that interpretation of PET findings is complicated by coexistent epilepsy, which was not in fact the case.Read the original article.&nbsp

Chronic peripheral inflammation is associated with impaired functional remission independently of symptomatic remission and depression in schizophrenia

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Virtual human as a new diagnostic tool, a proof of concept study in the field of major depressive disorders

Embodied Conversational Agents (ECAs) are promising software to communicate with patients but no study has tested them in the diagnostic field of mental disorders. The aim of this study was 1) to test the performance of a diagnostic system for major depressive disorders (MDD), based on the identification by an ECA of specific symptoms (the MDD DSM 5 criteria) in outpatients; 2) to evaluate the acceptability of such an ECA. Patients completed two clinical interviews in a randomized order (ECA versus psychiatrist) and filled in the Acceptability E-scale (AES) to quantify the acceptability of the ECA. 179 outpatients were included in this study (mean age 46.5 ± 12.9 years, 57.5% females). Among the 35 patients diagnosed with MDD by the psychiatrist, 14 (40%) patients exhibited mild, 12 (34.3%) moderate and 9 (25.7%) severe depressive symptoms. Sensitivity increased across the severity level of depressive symptoms and reached 73% for patients with severe depressive symptoms, while specificity remained above 95% for all three severity levels. The acceptability of the ECA evaluated by the AES was very good (25.4). We demonstrate here the validity and acceptability of an ECA to diagnose major depressive disorders. ECAs are promising tools to conduct standardized and well-accepted clinical interviews

Prospective view on sound synthesis BCI control in light of two paradigms of cognitive neuroscience

International audienceDifferent trends and perspectives on sound synthesis control issues within a cognitive neuroscience framework are addressed in this article. Two approaches for sound synthesis based on the modelling of physical sources and on the modelling of perceptual effects involving the identification of invariant sound morphologies (linked to sound semiotics) are exposed. Depending on the chosen approach, we as- sume that the resulting synthesis models can fall under either one of the theoretical frameworks inspired by the representational-computational or enactive paradigms. In particular, a change of viewpoint on the epistemological position of the end user from a third to a first person, inherently involves different conceptualizations of the interaction between the listener and the sounding object. This differentiation also influences the design of the control strategy enabling an expert or an intuitive sound manipulation. Finally, as a perspective to this survey, Explicit and Implicit Brain Control Interfaces (BCI) are described with respect to the previous theoreti- cal frameworks, and a semiotic-based BCI aiming at increasing the intuitiveness of synthesis control processes is envisaged. These interfaces may open for new appli- cations adapted to either handicapped or healthy subjects