414 research outputs found
Lateral asymmetry in the hippocampal response to the remoteness of autobiographical memories
No full textThe time scale of hippocampal involvement in retrieving memories, particularly those more remote, is still a matter of debate. Some propose that the hippocampus is not involved in the retrieval of remote memories, whereas others assert that it is necessary for memory retrieval in perpetuity. Functional magnetic resonance imaging was used to examine the effect of remoteness on the neural basis of memory. We used a parametric event-related random-effects design in a large group of subjects to overcome some of the limitations of previous neuroimaging studies. We found that the hippocampi were significantly active during the retrieval of autobiographical memories. Notably, the two hippocampi diverged in their responses to remoteness. The right hippocampus showed a temporal gradient, decreasing in activity the more remote the autobiographical memories. No such effect was apparent in the left hippocampus, suggesting its invariant involvement in remembering autobiographical events throughout the lifespan. The dorsal amygdalas showed a temporal gradient similar to the right hippocampus, but emotional valence and intensity were not directly associated with changes in activity. The current results indicate that consideration of lateral asymmetry may help to broaden the scope of theoretical interpretations concerning hippocampal involvement in remote memory
Mechanisms of control
No full textThis chapter is mainly concerned with functional imaging studies that illustrate different approaches to the study of control mechanisms. The prefrontal cortex does not act by itself. The executive properties of prefrontal cortex emerge through interactions with other brain areas. However, in this chapter we are largely concerned with attempts to assign specific control functions to different regions of prefrontal cortex. First, it discusses why it has proved so difficult to anatomize prefrontal function. The main problem with prefrontal cortex is that no obvious mapping has been found between subregions and function. Then it focuses on the evidence for functional specialization in prefrontal cortex. This chapter further discusses imaging frontal tasks. This includes the Wisconsin Card Sorting test (WCST), the Tower of London (TOL) task, and the Stroop Task. If one is to understand the role of prefrontal cortex in higher cognitive functions one need to take into account a much wider range of evidence. One needs to be much more precise in characterization of cognitive functions and much more accurate in the localization of brain activity
Neuropsychologie et tentatives de modélisation des déficits de la cognition schizophrénique — A propos de l’ouvrage de Christopher D. Frith The cognitive neuropsychology of schizophrenia, 1992, traduit aux Presses Universitaires de France par Bernard Pachoud et Catherine Bourdet : Neuropsychologie cognitive de la schizophrénie, 1996, collection "Psychiatrie ouverte".
No full textNeuropsychology and attempts to model deficits in schizophrenic cognition. Frith’s model systematically admits that schizophrenics demonstrations come from a dysfonction about mecanisms and processes which are involved in initiative, monitoring and regulation of action. His contribution subscribes to neuropsychological perspective and is concerned with mental and cerebral processes association in the way that schizophrenics signs and symptoms rely to cerebral anomaly. We discuss this kind of epistemology and compare axioms it takes for granted with fonctionalism theory. Then as we look schizophrenia’s pragmatic approach into question we take care on aspects of methodological arguments and theoretical interpretations the author argues for negative and positive schizophrenic symptoms. The fact is that pragmatics draws on complicated mental processes and sometimes concludes against the author’s point of view or sometimes agrees.Le modèle de Frith exploite de manière systématique l’hypothèse selon laquelle les manifestations schizophréniques ont leur origine dans un dysfonctionnement des mécanismes et des processus impliqués dans l’initiation, le contrôle et la régulation de l’action. Il s’inscrit dans la tradition neuropsychologique et étudie le rapport processus mentaux / processus cérébraux en associant les signes et symptômes schizophréniques à une anomalie des fonctions cérébrales. Nous discutons cette épistémologie en comparant certains de ses présupposés à ceux du courant fonctionnaliste. Nous abordons enfin précisément quelques aspects de la méthodologie et des interprétations théoriques de l’auteur à propos de certains symptômes négatifs et positifs de la schizophrénie selon son point de vue et selon le point de vue tantôt complémentaire, tantôt antagoniste, des approches pragmatiques de la schizophrénie qui ont pour particularité de traiter des opérations mentales complexes.Musiol Michel. Neuropsychologie et tentatives de modélisation des déficits de la cognition schizophrénique — A propos de l’ouvrage de Christopher D. Frith The cognitive neuropsychology of schizophrenia, 1992, traduit aux Presses Universitaires de France par Bernard Pachoud et Catherine Bourdet : Neuropsychologie cognitive de la schizophrénie, 1996, collection "Psychiatrie ouverte". In: Intellectica. Revue de l'Association pour la Recherche Cognitive, n°28, 1999/1. Présences de la Gestalt, sous la direction de R. Casati. pp. 251-273
Action generation and action perception in imitation: an instance of the ideomotor principle
No full textItem does not contain fulltextWe review a series of behavioural experiments on imitation in children and adults that test the predictions of a new theory of imitation. Most of the recent theories of imitation assume a direct visual-to-motor mapping between perceived and imitated movements. Based on our findings of systematic errors in imitation, the new theory of goal-directed imitation (GOADI) instead assumes that imitation is guided by cognitively specified goals. According to GOADI, the imitator does not imitate the observed movement as a whole, but rather decomposes it into its separate aspects. These aspects are hierarchically ordered, and the highest aspect becomes the imitator's main goal. Other aspects become sub-goals. In accordance with the ideomotor principle, the main goal activates the motor programme that is most strongly associated with the achievement of that goal. When executed, this motor programme sometimes matches, and sometimes does not, the model's movement. However, the main goal extracted from the model movement is almost always imitated correctly
Kinds of Access:Different Methods for Report Reveal Different Kinds of Metacognitive Access
No full textIn experimental investigations of consciousness, participants are asked to reflect upon their own experiences by issuing reports about them in different ways. For this reason, a participant needs some access to the content of her own conscious experience in order to report. In such experiments, the reports typically consist of some variety of ratings of confidence or direct descriptions of one’s own experiences. Whereas different methods of reporting are typically used interchangeably, recent experiments indicate that different results are obtained with different kinds of reporting. We argue that there is not only a theoretical, but also an empirical difference between different methods of reporting. We hypothesise that differences in the sensitivity of different scales may reveal that different types of access are used to issue direct reports about experiences and metacognitive reports about the classification process
Metacognition and Confidence in Value-Based Choice
No full textBasic psychophysics tells us that decisions are rarely perfect: even with identical stimuli choice accuracy fluctuates and errors are often made. Metacognition allows appraisal of this uncertainty and correction of errors. For more complex value-based choices, however, metacognitive processes are poorly understood. In particular, how subjective confidence and valuation of choice options interact at the level of brain and behaviour is unknown. In this chapter, we summarise and discuss the results of a study designed to investigate this relationship. Subjects were asked to choose between pairs of snack items and subsequently provide a confidence rating in their choice. As predicted by a computational model of the decision process, confidence reflected the evolution of a decision variable over time, explaining the observed relation between confidence, value, accuracy and reaction time (RT). Furthermore, fMRI signal in human ventromedial prefrontal cortex (vmPFC) reflected both value comparison and confidence in the value comparison process. In contrast, individuals’ metacognitive ability was predicted by a measure of functional connectivity between vmPFC and rostrolateral prefrontal cortex (rlPFC), a region that responded to changes in confidence but was not involved in representing the values used to guide choice. These results provide a novel link between noise in value comparison and metacognitive awareness of choice, extending the study of metacognition to value-based decision-making
À propos de la modélisation cognitive de la schizophrénie. « De Frith à nos jours, actualisations ou nouveaux paradigmes ? ». Une revue de littérature systématique.
No full textCette thèse s’intéresse à la modélisation cognitive de la schizophrénie et particulièrement à sa capacité intégrative, c’est-à-dire sa capacité à expliquer et prendre en compte l’ensemble des phénotypes et endophénotypes schizophréniques par des hypothèses concernant des déficits cognitifs précis. Cela pose en soi la question de la pertinence du diagnostic actuel de schizophrénie. Le modèle de référence initial choisi est celui de Christopher-D FRITH de 1992. La question était de savoir si depuis cette théorisation la modélisation cognitive de la schizophrénie avait évolué et si ces évolutions étaient des actualisations ou si de nouveaux paradigmes étaient apparus. Nous avons pour cela effectué une revue de littérature systématique des articles concernant le sujet, commençant par le livre de Christopher-D FRITH de 1992. Nous nous appliquons d’abord à définir les notions de phénotype et endophénotype concernant la schizophrénie. Puis nous tentons de définir précisément,d’après l’état de la science, les phénotypes et endophénotypes schizophréniques. Nous évoquons la notion de spectre et d’évolutivité de la maladie, avec notamment les EMR, les personnalité schizotypiques et les apparentés sains. Nous arrivons au fait que ces endophénotypes sont des marqueurs et des facteurs de risque de la schizophrénie telle que définie par le DSM5 et qu’ils sont retrouvés sur l’ensemble du spectre. Cela donne une pertinence au concept de schizophrénie et de spectre schizophrénique. Par la suite nous nous intéressons aux différents modèles cognitifs intégratifs de la schizophrénie en commençant par celui de Christopher-D FRITH de 1992 concernant les métareprésentations, le self-monitoring et la théorie de l’esprit. Puis nous avons sélectionnés et évalués les modèles cognitifs se voulant intégratifs,de FRITH à nos jours, qui nous semblaient pertinents. Nous avons ainsi étudié : le modèle de la déconnexion de FRISTON, le codage prédictif non Bayésien de HEMSLEY et KRISHNAN, la dysmétrie cognitive d’ANDREASEN, les troubles de la conscience autonoétique de DANION, les hypothèses d’anomalies d’intégration du contexte de HARDY-BAYLE, SARFATI, BARCH et al.,la saillance aberrante des stimuli de KAPUR, le codage prédictif Bayésiennotamment avec FLETCHER et ADAMS, le concept d’action orientée vers un but, les diverses actualisations du modèle de FRITH et les perturbations d’accès à la conscience de DEHAENE et al.. Nous avons tenté de les comparer par leur caractère intégratif en synthétisant dans un tableau le fait que les modèles expliquent ou prennent en compte ou non les différents caractères phénotypiques et endophénotypiques que nous avions définis au préalable. Nous arrivons à la conclusion que le modèle de FRITH a été actualisé depuis 1992 et que d’autres modèles ont été proposés de manière plus ou moins satisfaisante. Ces actualisations ont permis une avancée et une précision certaine des concepts. Cependant nous notons que le codage prédictif, le modèle Bayésien et le codage de l’incertitude sont de nouveaux paradigmes permettant une explication plus précise et intégrative des phénotypes et endophénotypes schizophréniques. De plus, le modèle de FRITH de 1992 a intégré et a été intégré au modèle de la déconnexion de FRISTON. L’ensemble a été complété grâce à FLETCHER et ADAMS par le modèle du codage prédictif Bayésien. Le modèle en résultant permet d’expliquer la variabilité phénotypique d’un individu à l’autre et chez un même individu ainsi que l’intégration des notions de spectre schizophrénique et d’EMR. Ce modèle fait aussi le lien avec la génétique et la neurobiologie supposées sous-jacentes aux troubles. Ces théories cognitives actuelles peuvent être modélisées par ordinateur ce qui permet la vérification précise de leurs hypothèses. Nous suggérons que ces modèles et leurs théories devraient être recoupés avec les initiatives RDoC tentant de se détacher du DSM5 afin d’être plus objectifs. Leur évaluation devrait aussi s’appuyer sur des critères objectifs tels que ceux proposés par la MATRICS.Ces différentes théories évoquent pour nous l’importance d’en déduire de nouvelles approches thérapeutiques de TCC et de remédiation cognitive. La pleine conscience, les thérapies ACT et le yoga nous semblent d’intérêt à être modélisés en lien avec ces modèles pour être appliqués de manière efficace
Social interaction modifies neural response to gaze shifts
No full textMonitoring gaze shifts is important for social interactions. The direction of gaze can reveal intentions and help to predict future actions. Here we examined whether behavioural and neural responses to gaze shifts were modulated by the social context of the gaze shift in two linked experiments. Two faces were presented, one gazing directly at the subject (the 'social' face) and one with averted gaze (the 'unsocial' face). One face then made a gaze shift that was either towards a visible target ('correct') or towards another location in space ('incorrect'). Both behavioural and neural responses to gaze shifts were modulated by the social context and the goal directedness of the gaze shift. Reaction times were significantly faster in response to 'correct' and 'social' compared with 'incorrect' and 'unsocial' gaze shifts, respectively. Using functional magnetic resonance imaging, we found significantly greater activation in the parieto-frontal attentional network, and in some parts of the posterior superior temporal sulcus, in response to 'incorrect' and 'unsocial' compared with 'incorrect' and 'social' gaze shifts, respectively. Conversely, we found greater activation in the medial prefrontal cortex and precuneus in response to 'correct' and 'social' compared with 'incorrect' and 'unsocial' gaze shifts. This activity may reflect the experience of joint attention associated with these gaze shifts
Comment on "Wandering minds: The default network and stimulus-independent thought"
No full textMason et al. (Reports, 19 January 2007, p. 393) attributed activity in certain regions of the "resting" brain to the occurrence of mind-wandering. However, previous research has demonstrated the difficulty of distinguishing this type of stimulus-independent thought from stimulus-oriented thought (e.g., watchfulness). Consideration of both possibilities is required to resolve this ambiguity
Non-alcoholic fatty liver disease in older people
No full textBackgroundNon-alcoholic fatty liver disease (NAFLD) is principally a disease of middle and old age. Previous studies reported it to be benign in old age, however more recent studies suggest an increased mortality in the >60-year-olds.ObjectivesTo define the prevalence of risk factors and the laboratory and histological differences between different age groups with NAFLD, in order to confirm/refute findings in previous smaller studies.MethodsRetrospective, cohort study set in a tertiary liver clinic in the UK. 351 consecutive patients with biopsy-proven NAFLD were divided into an older (> or =60), a middle-aged (> or =50 to ResultsOlder patients had significantly more risk factors (hypertension, obesity, diabetes, hyperlipidaemia). Albumin, alanine aminotransferase (ALT), ALT/aspartate aminotransferase ratio and platelets significantly reduced with advancing age. MCV and alkaline phosphatase significantly increased with increasing age. Older patients had significantly greater fibrosis on biopsy with less percentage fat, with the cirrhotic patients being significantly older than non-cirrhotics. Insulin resistance was similar in younger and older groups.ConclusionNAFLD affects mainly the middle-aged and the elderly. With advancing age come more risk factors for its development. Older patients show more severe biochemical, haematological and histological changes, with cirrhotics having a significantly greater age than those with milder disease.James Frith, Christopher P. Day, Elsbeth Henderson, Alastair D. Burt, Julia L. Newto
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