Interactions équilibration et cognition

International audienceDans ce chapitre, nous rappelons le rôle des systèmes sensoriels dans les performances de posture, d’équilibration et de marche, nous précisons les fonctions cognitives susceptibles d’avoir un impact sur ces régulations et proposons un modèle théorique d'interactions posture-cognition. L'implication cognitive dans le contrôle postural est classiquement étudiée dans des situations de double-tâches qui consistent le plus souvent en la réalisation simultanée d’une tâche posturale et d’une tâche cognitive. Cette situation de doubles-tâches présente un effet délétère du fait du surcoût attentionnel. Le système cognitif humain ayant des capacités limitées, nous proposons que la réalisation simultanée de deux tâches dépend de la capacité de chaque sujet de réaliser ces tâches selon un continuum compris entre une réalisation automatique jusqu’à une réalisation hautement contrôlée. Un niveau de contrôle maximal dépasse les capacités attentionnelles du sujet rendant la réalisation simultanée de ces deux tâches impossibles. Le sujet priorise alors une des deux tâches. Ces situations de double-tâches fournissent également une base théorique pour expliquer certains changements posturo-locomoteurs observés chez le sujet âgé, de même que les difficultés d'équilibration chez les sujets âgés dits "chuteurs", ou encore diverses modifications du contrôle postural intervenant après atteinte sensorielle périphérique. Parmi la vaste littérature sur les double-tâches, nous rapportons des travaux représentatifs des relations entre différentes composantes cognitives et leurs conséquences sur le contrôle de la posture et de la marche, chez l'adulte jeune, au cours du vieillissement, chez des sujets chuteurs ou dont les capacités sensorimotrices sont altérées, et chez des personnes dont les capacités cognitives sont altérées. Récemment, cette relation posture-cognition a été envisagée de façon nouvelle. Nous décrivons ici comment un entraînement cognitif est capable de favoriser une meilleure gestion de la double-tâche et précisons les mécanismes cognitifs qui seraient responsables d’un meilleur équilibre postural

Gene regulation in the rat prefrontal cortex after learning with or without cholinergic insult

International audienceThe prefrontal cortex is essential for a wide variety of higher functions, including attention and memory. Cholinergic neurons are thought to be of prime importance in the modulation of these processes. Degeneration of forebrain cholinergic neurons has been linked to several neurological disorders. The present study was designed to identify genes and networks in rat prefrontal cortex that are associated with learning and cholinergic-loss-memory deficit. Affymetrix microarray technology was used to screen gene expression changes in rats submitted or not to 192 IgG-saporin immunolesion of cholinergic basal forebrain and trained in spatial/object novelty tasks. Results showed learning processes were associated with significant expression of genes, which were organized in several clusters of highly correlated genes and would be involved in biological processes such as intracellular signaling process, transcription regulation, and filament organization and axon guidance. Memory loss following cortical cholinergic deafferentation was associated with significant expression of genes belonging to only one clearly delineated cluster and would be involved in biological processes related to cytoskeleton organization and proliferation, and glial and vascular remodeling, i.e., in processes associated with brain repair after injury. (C) 2011 Elsevier Inc. All rights reserved

Quel impact des stéréotypes négatifs du vieillissement sur l’équilibration ?

International audienc

Gene expression profile in rat hippocampus with and without memory deficit

International audienceThe cholinergic neuronal system, through its projections to the hippocampus, plays an important role in learning and memory. The aim of the study was to identify genes and networks in rat hippocampus with and without memory deficit. Genome-scale screening was used to analyze gene expression changes in rats submitted or not to intraparenchymal injection of 192 IgG-saporin and trained in spatial/object novelty tasks. Results showed learning processes were associated with significant expression of genes that could be grouped into several clusters of similar expression profiles and that are involved in biological functions, namely lipid metabolism, signal transduction, protein metabolism and modification, and transcription regulation. Memory loss following hippocampal cholinergic deafferentation was associated with significant expression of genes that did not show similar cluster organization. Only one cluster of genes could be identified; it included genes that would be involved in tissue remodeling. More important, most of the genes significantly altered in lesioned rats were down-regulated. (c) 2010 Elsevier Inc. All rights reserved

Time course of behavioral changes following basal forebrain cholinergic damage in rats : environmental enrichment as a therapeutic intervention

International audienceThe present experiment was designed to study changes in behavior following immunolesioning of the basal forebrain cholinergic system. Rats were lesioned at 3 months of age by injection of the 192 IgG-saporin immunotoxin into the medial septum area and the nucleus basalis magnocellularis, and then tested at different times after surgery (from days 7-500) on a range of behavioral tests, administered in the following order: a nonmatching-to-position task in a T-maze, an object-recognition task, an object-location task, and an open-field activity test. The results revealed a two-way interaction between post-lesion behavioral testing time and memory demands. In the nonmatching-to-position task, memory deficits appeared quite rapidly after surgery, i.e. at a post-lesion time as short as 1 month. In the object-recognition test, memory impairments appeared only when rats were tested at late post-lesion times (starting at 15 months), whereas in the object-location task deficits were apparent at early post-lesion times (starting from 2 months). Taking the post-operative time into account, one can hypothesize that at the shortest post-lesion times, behavioral deficits are due to pure cholinergic depletion, while as the post-lesion time increases, one can speculate the occurrence of a non-cholinergic system decompensation process and/or a gradual degeneration process affecting other neuronal systems that may contribute to mnemonic impairments. Interestingly, when middle-aged rats were housed in an enriched environment, 192 IgG-saporin-lesioned rats performed better than standard-lesioned rats on both the non matching-to-position and the object-recognition tests. Environment enrichment had significant beneficial effects in 192 IgG-saporin-lesioned rats, suggesting that lesioned rats at,late post-lesion times (over 1 year) still have appreciable cognitive plasticity

Benefits of computer-based memory and attention training in healthy older adults

International audienceMultifactorial cognitive training programs have a positive effect on cognition in healthy older adults. Among the age-sensitive cognitive domains, episodic memory is the most affected. In the present study, we evaluated the benefits on episodic memory of a computer-based memory and attention training. We targeted consciously controlled processes at encoding and minimizing processing at retrieval, by using more familiarity than recollection during recognition. Such an approach emphasizes processing at encoding and prevents subjects from reinforcing their own errors. Results showed that the training improved recognition performances and induced near transfer to recall. The largest benefits, however, were for tasks with high mental load. Improvement in free recall depended on the modality to recall; semantic recall was improved but not spatial recall. In addition, a far transfer was also observed with better memory self-perception and self-esteem of the participants. Finally, at 6-month follow up, maintenance of benefits was observed only for semantic free recall. The challenge now is to corroborate far transfer by objective measures of everyday life executive functioning

A comprehensive approach to study the resting-state brain network related to creative potential

International audienceStudies related to creativity generally investigate brain activity at rest using raw scores from only one creative task. However, considering all the factors that can impact the creative product, we believe that the creative potential of individuals must be evaluated to identify the associated resting-state brain networks. Moreover, studying the brain functional connectivity related to creativity processes should be considered in conjunction with cognitive functioning as both are composite phenomena. To test this assumption, in this exploratory study, we differentiated high- and low-creativity potential people with a cognitive functioning approach using structural equation modeling assuming an influence of working memory (WM) and analytical thinking on creativity assessed by the Torrance Tests of Creative Thinking. Then, we examined brain functional connectivity at rest and found that highly creative people had increased connectivity in the attentional network (AN), the default-mode network (DMN) and a decrease in the salience network (SN). Our findings highlight the involvement of the AN, which is very scarcely mentioned in the literature. We therefore linked this network to creative potential, which is consistent with cognitive theories suggesting that creativity is underpinned by attentional processes. Furthermore, studying creativity with an approach based on a model of cognitive functioning seems more consistent with how connectivity data are processed