Denis Brouillet

Existe-t-il un déficit d'inhibition lors du vieillissement ? Confrontation de l'hypothèse dorso-ventrale et de l'hypothèse frontale dans l'effet d'amorçage négatif

Resume L’evaluation des processus d’inhibition a une place centrale en neuropsychologie comme en psychopathologie. De nombreux praticiens et chercheurs tiennent pour acquis qu’un deficit d’inhibition peut etre evoque pour rendre compte des performances lors du vieillissement normal et pathologique. Si les fonctions essentielles remplies par les mecanismes inhibiteurs sont largement detaillees dans la litterature, la nature precise des processus sous-jacents mis en jeu demeure peu abordee. A ce propos, dans un article de 1997, Burke (4) met en exergue l’urgence de se concentrer sur une specification de la theorie de l’inhibition qui demeure a ce jour vague et intuitive. Autrement dit, les phenomenes inhibiteurs observes sur les performances (ie ralentissement des temps de reponse) ne sont pas interpretables de facon univoque par l’existence de processus cognitifs inhibiteurs centraux. Ceci est d’autant plus vrai dans le contexte de l’amorcage negatif, paradigme couramment employe lors de protocoles hospitaliers de recherche clinique (notamment en neuropsychologie et psychopathologie). Selon l’interpretation dorso-ventrale de l’amorcage negatif, il existe 2 processus d’inhibition independants, l’un base sur la localisation, l’autre sur l’identite des informations. Neanmoins, la question de la multiplicite des fonctions inhibitrices et de la validite psychologique de l’inhibition comme processus organisateur de la pensee demeure a ce jour source d’oppositions. Pour notre part, nous proposons qu’une approche de l’inhibition en termes de niveaux de traitement autorise une comprehension unitaire et automatique de cette derniere. Nous defendons ainsi l’hypothese frontale de l’amorcage negatif selon laquelle la capacite a inhiber depend des capacites de controle et de maintien des objectifs des individus. Dans ce but, nous avons realise 2 experiences a partir d’une version modifiee du paradigme d’amorcage negatif associe a une tâche de categorisation sur le genre. Nous montrons que la compatibilite des couples amorce/cible donne lieu a un ralentissement des temps de decision comparativement a une condition incompatible. Nous appelons ce ralentissement Effet de compatibilite negative (NCE) que nous interpretons comme etant un indicateur de la mise en œuvre d’un mecanisme d’inhibition automatique. Le profil des performances entre jeunes et âges ne differe pas des lors que la tâche necessite peu d’attention controlee (experience 1). En revanche, les personnes âgees ne presentent pas de NCE des lors que la tâche est complexe (experience 2). Notre travail suggere qu’il est essentiel de prendre en compte la capacite generale des sujets, notamment leur capacite a maintenir les buts en cours, lorsque nous postulons qu’il existe un deficit d’inhibition lors du vieillissement. Nous discutons de ces resultats au regard de la theorie des niveaux de traitement et des donnees recentes issues de la neuro-imagerie.

Inhibition des réponses automatiques au test du Hayling dans la schizophrénie

OBJECTIVESnIn schizophrenia, alteration in the prefrontal cortex can induce some deficiencies of the executive functions, and among them errors in inhibition of prepotent responses. This type of inhibitory processes was called restraint function by Hasher et al. It implies a conscious and voluntary inhibition which demands attentional resources. Among the tasks exploring this function, the Hayling completion sentence task (Burgess and Shallice) appears to be the most specific. Moreover, healthy subjects performing this task in functional magnetic resonance imaging (fMRI) show activation of the prefrontal cortex. In this study, we investigated inhibitory processes in schizophrenic patients using two versions of the Hayling completion sentence task, a behavioural version and an fMRI version in order to assess both performance levels and brain correlates of inhibitory processes.nnnMETHODSnForty-eight schizophrenic participants according to DSM-IV, (mean age: 32.8, S.D. 7.7), stabilized for at least one month, receiving antipsychotic medication and with IQ higher than 70 (mean: 96.86, S.D. 20.67) and education level (mean: 11.15, S.D. 3.26) participated in the behavioural study. They were matched on age (mean: 33.8, S.D. 7.6) and education level (mean: 12.28, S.D. 2.87) with thirty-two healthy controls. Nineteen of schizophrenic participants (mean age: 33, S.D. 6.9 and IQ: 99, S.D. 10.74) were assessed by an fMRI adaptation of the Hayling task, matched with 12 controls (mean: 33.9, S.D. 7.3). All the participants had to perform the Hayling task and a speed accuracy task. The Hayling task consists in sentences for which the last word is missing. In the initiation condition, the participants had to complete the sentence with the appropriate word, whereas in inhibition condition the participants had to complete the sentence with inappropriate and unrelated words.nnnRESULTSnCompared to controls, schizophrenics showed an increased number of errors in the inhibition of prepotent responses associated with increased reaction times, even when considering information processing speed. fMRI results showed fairly similar frontal activations in both groups. Nevertheless, schizophrenic patients presented principally large activations in dorsolateral and ventrolateral frontal cortex, the superior frontal sulcus, the frontal pole and the premotor cortex, and stronger activations (bilateral) in the posterior parietal cortex. Control subjects demonstrated a network of deactivated brain regions whereas the schizophrenics did not.nnnDISCUSSIONnOur results are in favour of poorer efficacy of restraint function, sometimes comprising impairment of inhibitory processes inducing errors in schizophrenics. This deficiency might be considered as insufficiency in attentional resources and/or in working memory. Hence patients cannot simultaneously restrain prepotent response and find appropriate controlled strategy for correct completion of the task. Moreover, bilateral patterns of parietal hyperactivation and absence of patterns of deactivation seem also in favour of an attentional hypothesis. The Hayling task might be interesting for assessment of inhibitory processes in schizophrenia.

Évaluation du traitement des traits perceptifs des concepts vivants et non vivants lors du vieillissement normal et de la maladie d'Alzheimer

Le present travail vise a etudier linfluence du facteur distinctivite sur le traitement des concepts vivants et non vivants au cours du vieillissement normal et pathologique, en particulier au regard des propositions de lapproche de la structure conceptuelle. Nous avons ainsi soumis une epreuve de verification de proprietes perceptives a des adultes jeunes, âges et a des patients atteints de maladie dAlzheimer. Les resultats observes sont globalement en desaccord avec les propositions du modele. Ils montrent cependant que la distinctivite est un facteur sensible au vieillissement conceptuel normal et pathologique. Une alteration progressive du domaine vivant au cours de la pathologie est egalement observee. Lensemble de ces resultats ainsi que notre procede devaluation de la memoire semantique sont discutes au regard des implications fondamentales et appliquees quils soulevent.

When the vibrations allow for anticipating the force to be produced: an extend to Pfister et al. (2014)

According to the ideomotor theory, action selection is done by the mental anticipation of its perceptual consequences. If the distal information processed mainly by vision and hearing are considered essential for the representation of the action, the proximal information processed by the sense of touch and proprioception is of less importance. Recent works seem to show the opposite. Nevertheless, it is necessary to complete these results by offering a situation, more ecological, where response and effect can occur on the same effector. So, the goal of our work was to implement a more relevant spatial correspondence because to touch is not the same action that to hear or to see. To do so, participants pressed a specific key after the presentation of a stimulus. The key vibrated depending on the pressure exerted on it. In a compatible condition, high pressure on a key triggered a high vibration, while in an incompatible condition high pressure triggered a low vibration on the same effectors. As expected, the response times were faster in the compatible condition than the incompatible condition. This means that proximal information participates actively in the selection of action.

Rencontre entre memoire et controle chez des jeunes et des aines : la naissance d'une plainte ?

The aim of this study is to explore cognitive complaint by investigating the influence of memory controlled processes (recollection) and metacognitive beliefs. Several methodological precautions were taken in order to control neuropsychological and psychopathological criteria, like anxiety, depression or objective memory trouble. The habit paradigm (Hay & Jacoby, 1999) was used to create a memory slips task, and to estimate the contributions of recollection and habit to performance. Besides, participants were asked to complete questionnaires in order to assess cognitive complaint (CDS) and metacognitive beliefs (MCQ). Results showed that neither cognitive complaint nor metacognitive beliefs differed significantly between young and older persons. However, statistical analysis did show cognitive dissociations in function of cognitive complaint. Finally, depressive affects, memory controlled processes and metacognitive beliefs about the controllability of thoughts appeared as good predictors of memory complaint. In spite of our study limitations, we discuss our results in terms of clinical implications.The aim of this study is to explore cognitive complaint by investigating the influence of memory controlled processes (recollection) and metacognitive beliefs. Several methodological precautions were taken in order to control neuropsychological and psychopathological criteria, like anxiety, depression or objective memory trouble. The habit paradigm (Hay & Jacoby, 1999) was used to create a memory slips task, and to estimate the contributions of recollection and habit to performance. Besides, participants were asked to complete questionnaires in order to assess cognitive complaint (CDS) and metacognitive beliefs (MCQ). Results showed that neither cognitive complaint nor metacognitive beliefs differed significantly between young and older persons. However, statistical analysis did show cognitive dissociations in function of cognitive complaint. Finally, depressive affects, memory controlled processes and metacognitive beliefs about the controllability of thoughts appeared as good predictors of memory complaint. In spite of our study limitations, we discuss our results in terms of clinical implications.Cette étude explore la plainte cognitive en investiguant notamment linfluence des processus contrôlés en mémoire et des croyances métacognitives. Les participants de notre population ne présentaient ni dépression, ni anxiété, ni trouble mnésique significatifs. Nous avons créé une tâche de « glissement de mémoire » pour estimer linfluence de la récupération consciente du souvenir dans la performance (Hay et Jacoby, 1999). Des questionnaires auto-administrés nous ont permis dévaluer la plainte cognitive (EDC) et les croyances métacognitives (MCQ). Comme nous lavions prédit, les différentes analyses statistiques réalisées confirment lexistence de dissociations cognitives en fonction de la plainte cognitive des participants. Nos résultats montrent que les affects dépressifs constituent une variable explicative de la plainte mnésique tout autant que les processus contrôlés en mémoire et le sentiment subjectif de contrôle. Nonobstant les limites de cette étude, nous discutons nos résultats en termes dimplications cliniques.