Search

Age-related differences in visual search have been extensively studied using simple item arrays, showing an attentional decline. Little is known about how aging affects attentional guidance during search in more complex scenes. To study this issue, we analyzed eye-movement behavior in realistic scene search. We examined age-related differences in top-down guidance, manipulating target template specificity (picture vs. word cue) and target-scene semantic consistency (consistent vs. inconsistent), and in bottom-up guidance, manipulating perceptual salience (high vs. low) of targets and distractors. Compared to young adults (YA), older adults (OA) were overall slower, from the first saccade in the scene. They showed a smaller benefit of a specific target template, suggesting that precision of visual information in working memory may decrease with age. The benefit of semantic consistency did not depend on age, suggesting a preserved ability in OA to use knowledge about object occurrence in scenes. OA showed greater bottom-up search facilitation due to target's high salience, which may depend on reduced selection of low-salience stimuli. Attentional capture by distractors was greater in OA than YA, with respect to engagement (probability of distractor fixation), but only following a picture cue, and disengagement (fixation duration on distractors) in all conditions. Overall, our study shows that age-related differences in visual selection of targets and distractors depend on specific task demands in terms of top-down and bottom-up guidance. It also indicates that scene search difficulties in OA can be limited by cognitive and perceptual forms of environmental support. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Objective: Visual search is a crucial task in daily life, but in Alzheimer’s disease (AD) it has usually been investigated using simple arrays. Here, we used scenes depicting real environments and studied the time course of attentional guidance. Method: We analyzed eye-movement differences between mild AD patients and age-matched healthy controls during search. We examined top-down guidance, manipulating the target template (precise picture vs. word cue) and the target-scene semantic consistency (consistent vs. inconsistent), and bottom-up guidance, manipulating the perceptual salience (high vs. low) of targets and distractors. Results: During scene scanning, AD patients had longer search times, made more fixations before the first target fixation, and showed a greater probability of distractor selection, with longer distractor fixation. AD also led to longer target fixation. In patients and controls, picture cues and highly salient targets improved all search phases, whereas consistent targets only improved search initiation (first saccade). Moreover, top-down and bottom-up guidance interacted in initiation and scanning, and this did not differ between the two groups of participants. However, AD led to a smaller picture cue benefit in shortening distractor fixation and greater bottom-up search facilitation during scanning, where a high-salience target reduced the performance gap between patients and controls. Conclusions: Our study shows the importance of top-down and bottom-up guidance, and their integration, in improving search in AD patients. It suggests that precise target cues and, even more, highly salient targets may act as environmental supports that enhance attentional processing and search performance. (PsycInfo Database Record (c) 2022 APA, all rights reserved)

Nous avons la capacite de reconnaitre tres rapidement une scene visuelle, meme presentee un tres court instant. Cette capacite concerne le sens de la scene mais egalement l’emotion qu’elle vehicule. Cette revue critique presentera d’abord une synthese des principales recherches menees sur les traitements des contenus semantiques, puis sur les traitements des contenus emotionnels lors de la perception des scenes. Il s’agira de mieux comprendre comment ces informations sont selectionnees et representees, et comment elles influencent l’exploration visuelle, contribuant ainsi a la rapidite du traitement de la scene. Nous questionnerons ensuite les eventuelles interactions entre les traitements semantiques et emotionnels. Cette revue met en exergue l’importance des liens semantiques et emotionnels entre les differents constituants d’une scene et le caractere dynamique, integratif de la perception visuelle. Elle suggere egalement divers futurs axes de recherche.

Visual categorization improves when object-context associations in scenes are semantically consistent, thus predictable from schemas stored in long-term memory. However, it is unclear whether this is due to differences in early perceptual processing, in matching of memory representations or in later stages of response selection. We tested these three concurrent explanations across five experiments. At each trial, participants had to categorize a scene context and an object briefly presented within the same image (Experiment 1), or separately in simultaneous images (Experiments 2–5). We analyzed unilateral (Experiments 1, 3) and bilateral presentations (Experiments 2, 4, 5), and presentations on the screen’s horizontal midline (Experiments 1–2) and in the upper and lower visual fields (Experiments 3, 4). In all the experiments, we found a semantic consistency advantage for both context categorization and object categorization. This shows that the memory for object-context semantic associations is activated regardless of whether these two scene components are integrated in the same percept. Our study suggests that the facilitation effect of semantic consistency on categorization occurs at the stage of matching the percept with previous knowledge, supporting the object selection account and extending this framework to an object-context reciprocal influence on matching processes (object-context selection account).

International audience; The relationship between posttraumatic stress disorder (PTSD) and focal epilepsy is poorly understood. It has been hypothesized that there is a complex and reciprocal potential reinforcement of the symptoms of each condition. In this study, we investigated whether there are PTSD-specific brain changes in temporal lobe epilepsy (TLE). Brain fluorodeoxyglucose positron emission tomography (PET) metabolism was compared between controls and two groups of TLE patients: one group of 15 patients fulfilling the criteria for a potential diagnosis of PTSD (TLE-PTSD+), another group of 24 patients without a diagnosis of PTSD (TLE-PTSD-), and a group of 30 healthy control participants. We compared the differences in brain PET metabolism among these three groups, and we studied their correlations with interictal and peri-ictal scales of PTSD symptoms. TLE-PTSD+ patients showed more significant hypometabolism involving right temporal and right orbitofrontal cortex in comparison to TLE-PTSD- patients and healthy subjects. Moreover, degree of reduced metabolism in these brain areas correlated with interictal and peri-ictal PTSD questionnaire scores. PTSD in temporal epilepsy is associated with specific changes in neural networks, affecting limbic and paralimbic structures. This illustrates the close intertwining of epileptogenic and psychogenic processes in these patients

Visual search is a crucial, everyday activity that declines with ageing. Here, referring to the environmental support account, we hypothesised that semantic contextual associations between the target and the neighbouring objects (e.g., a teacup near a tea bag and a spoon), acting as external cues, may counteract this decline. Moreover, when searching for a target, viewers may encode information about the co-present distractor objects, by simply looking at them. In everyday life, where viewers often search for several targets within the same environment, such distractor objects may often become targets of future searches. Thus, we examined whether incidentally fixating a target during previous trials, when it was a distractor, may also modulate the impact of ageing on search performance. We used everyday object arrays on tables in a real room, where healthy young and older adults had to search sequentially for multiple objects across different trials within the same array. We showed that search was quicker (1) in young than older adults; (2) for targets surrounded by semantically associated objects than unassociated objects, but only in older adults; and (3) for incidentally fixated targets than for targets that were not fixated when they were distractors, with no differences between young and older adults. These results suggest that older viewers use both environmental support based on object semantic associations and object information incidentally encoded to enhance efficiency of real-world search, even in relatively simple environments. This reduces, but does not eliminate, search decline related to ageing.

Background Developmental dyslexia, a specific and long-lasting learning disorder that prevents children from becoming efficient and fluent readers, has a severe impact on academic learning and behavior and may compromise professional and social development. Most remediation studies are based on the explicit or implicit assumption that dyslexia results from a single cause related to either impaired phonological or visual-attentional processing or impaired cross-modal integration. Yet, recent studies show that dyslexia is multifactorial and that many dyslexics have underlying deficits in several domains. The originality of the current study is to test a remediation approach that trains skills in all three domains using different training methods that are tailored to an individual’s cognitive profile as part of a longitudinal intervention study. Methods This multicenter randomized crossover study will be conducted in three phases and will involve 120 dyslexic children between the ages of 8 and 13 years. The first phase serves as within-subject baseline period that lasts for 2 months. In this phase, all children undergo weekly speech-language therapy sessions without additional training at home (business-as-usual). During the second phase, all dyslexics receive three types of intensive interventions that last 2 month each: Phonological, visual-attentional, and cross-modal. The order of the first two interventions (phonological and visual-attentional) is swapped in two randomly assigned groups of 60 dyslexics each. This allows one to test the efficacy and additivity of each intervention (against baseline) and find out whether the order of delivery matters. During the third phase, the follow-up period, the intensive interventions are stopped, and all dyslexics will be tested after 2 months. Implementation fidelity will be assessed from the user data of the computerized intervention program and an “intention-to-treat” analysis will be performed on the children who quit the trial before the end. Discussion The main objective of this study is to assess whether the three types of intensive intervention (phase 2) improve reading skills compared to baseline (i.e., non-intensive intervention, phase 1). The secondary objectives are to evaluate the effectiveness of each intervention and to test the effects of order of delivery on reading intervention outcomes. Reading comprehension, spelling performance and reading disorder impact of dyslexic readers are assessed immediately before and after the multimodal intervention and 2 months post-intervention. Trial registration ClinicalTrials.gov, NCT04028310. Registered on July 18, 2019.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The goal of the current paper is to review the literature on the relationships between perceived control and episodic memory throughout adulthood. More specifically, three major questions are pursued: (1) Are higher levels of perceived control related to better memory performance? (2) Is the relationship between perceived control and memory similar or different as a function of age? (3) Does perceived control moderate memory decline? Although there is a great deal of evidence that perceived control and episodic memory are positively related in adulthood, the current review showed that very few studies have investigated whether age moderated this relationship. Moreover, only a limited number of studies have explored the role of perceived control in memory decline, and the results are inconsistent. We suggest some avenues for future research that could help understand by which mechanisms, and under what circumstances, perceived control and episodic memory are related across the lifespan.

Many studies provided the existence of attentional bias in individuals with post-traumatic stress-symptom (PTSS) or students with anxiety. However, results remain unclear concerning the type of alteration (vigilance or disengagement) and specificity of attentional bias (for negative information or trauma-related information). To address these issues, 131 students completed a visual search task with a lexical decision component and clinical scales (for PTSS and anxiety). Attentional bias (vigilance and disengagement) and word valences (neutral words, negative words and trauma-related words) were controlled. Three groups were distinguished: no symptom, PTSS and anxious groups. No symptom group was characterized by facilitation in the attentional treatment for negative information. PTSS group presented a disengagement bias for negative and trauma-related information. When anxiety symptoms were associated with PTSS, in this group, it led to difficulties in vigilance. The anxious group showed difficulties only for negative words in vigilance. These data suggest that sub-clinical PTSS and anxiety symptoms altered differently information processing. These findings highlight the need for research on trauma populations and anxiety, and to pursue studies on comorbidity in PTSS.

"Impairments in emotional information processing are frequently reported in attention deficit hyperactivity disorder (ADHD) at a voluntary, explicit level (e.g., emotion recognition) and at an involuntary, implicit level (e.g., emotional interference). Most of previous studies have used faces with emotional expressions, rarely examining other important sources of information usually co-occurring with faces in our every day experience. Here, we examined how the emotional content of an entire visual scene depicting real-world environments and situations is processed in ADHD. We systematically reviewed in PubMed, SCOPUS and ScienceDirect, using the PRISMA guidelines, empirical studies published in English until March 2019, about processing of visual scenes, with or without emotional content, in children and adolescents with ADHD. We included 17 studies among the 154 initially identified. Fifteen used scenes with emotional content (which was task-relevant in seven and irrelevant in eight studies) and two used scenes without emotional content. Even though the interpretation of the results differed according to the theoretical model of emotions of the study and the presence of comorbidity, differences in scene information processing between ADHD and typically developing children and adolescents were reported in all but one study. ADHD children and adolescents show difficulties in the processing of emotional information conveyed by visual scenes, which may stem from a stronger bottom-up impact of emotional stimuli in ADHD, increasing the emotional experience, and from core deficits of the disorder, decreasing the overall processing of the scene".

International audience; Anxiety and depression in epilepsy are strongly documented but post-traumatic stress disorder (PTSD) is underestimated and poorly known. We studied the links between psycho-traumagenic events (TE), onset of epilepsy, and severity of PTSD symptoms in patients with epilepsy. The study included 54 patients with epilepsy and 61 controls. We used validated questionnaires to screen for anxiety, depression, and PTSD symptoms and we conducted an interview to measure the prevalence of TE. We developed an original exploratory questionnaire to assess the presence of PTSD during interictal and peri-ictal periods. The results show that patients reported more exposure to a TE and presented significantly more severe PTSD symptoms than controls. Seventy-eight percent of patients (vs. 52% of controls) had been exposed to a TE, and 26% (vs. 7%) had a score above the diagnostic threshold of the PTSD scale. In addition, 18.6% of patients reported that their epilepsy began at the same time as they began to experience PTSD symptoms following a TE. Patients with high PTSD scores (above the threshold, n = 14) reported significantly more depression symptoms than patients without PTSD and reported PTSD symptoms both during the ictal and peri-ictal periods. Within the whole group of patients, anxiety (72%) and depression (33%) symptoms significantly correlated with PTSD symptoms reported by the scale. This study shows that patients with epilepsy have increased prevalence of self-reported PTSD symptoms. We describe the clinical picture specific to patients with epilepsy, which may include classical PTSD symptoms but also specific peri-ictal symptoms.

Regardez a gauche, maintenant regardez a droite, puis a gauche, a droite... C’est en substance ce qui est demande au participant dans la condition experimentale d’interet d’une etude qui explore les effets de series de mouvements oculaires saccadiques horizontaux (MOH) sur la performance cognitive, mnesique principalement. Des series breves (environ 30 secondes) de MOH precedant une tâche de memoire episodique semblent ameliorer la performance mnesique, en particulier chez les sujets fortement droitiers. Mais les quelques travaux menes selon ce devis general n’ont pas permis a ce jour de conclure, tantot montrant un effet positif des MOH sur la performance mnesique, et plus particulierement sur la recuperation en memoire episodique verbale, tantot echouant a mettre en evidence cet effet. Parce que la question de savoir si et comment les MOH peuvent moduler l’efficience cognitive nous parait d’un interet indeniable et sur le plan theorique et sur le plan clinique, nous nous proposons de faire le point. L’article presente les elements essentiels sur les bases cerebrales des saccades, un schema d’experience classique, les principaux resultats de la litterature et les differentes hypotheses en presence concernant les mecanismes cerebraux et cognitifs sous-jacents, encore tres preliminaires. Cette synthese souligne qu’il convient de suspendre notre jugement : les travaux encore peu nombreux, menes dans un nombre restreint d’equipes, n’ont pas produit de resultat robuste et seulement esquisse une comprehension des mecanismes d’action. Nous presenterons une demarche de recherche de type « collaboration contradictoire » qui nous a paru particulierement pertinente dans ce contexte. Enfin, comme il nous a semble indispensable de prendre en consideration les connexions entre cet axe de recherche sur les effets des mouvements oculaires sur le fonctionnement cognitif et cerebral et les etudes nombreuses sur l’efficacite des approches psychotherapeutiques qui utilisent ces mouvements, nous proposerons quelques considerations sur l’approche therapeutique par Eye Movement Desensitization and Reprocessing (EMDR).

International audience; Many instrumental activities of daily living (IADLs), like cooking and managing finances and medications, involve finding efficiently and in a timely manner one or several objects within complex environments. They may thus be disrupted by visual search deficits. These deficits, present in Alzheimer’s disease (AD) from its early stages, arise from impairments in multiple attentional and memory mechanisms. A growing body of research on visual search in AD has examined several factors underlying search impairments in simple arrays. Little is known about how AD patients search in real-world scenes and in real settings, and about how such impairments affect patients’ functional autonomy. Here, we review studies on visuospatial attention and visual search in AD. We then consider why analysis of patients’ oculomotor behavior is promising to improve understanding of the specific search deficits in AD, and of their role in impairing IADL performance. We also highlight why paradigms developed in research on real-world scenes and real settings in healthy individuals are valuable to investigate visual search in AD. Finally, we indicate future research directions that may offer new insights to improve visual search abilities and autonomy in AD patients.

International audience; The present study investigated the nature and specificity of the gestural deficit in children with developmental coordination disorder (DCD). Performance of children with DCD is compared with that of typically developing children across tasks and conditions that allow exploring distinct levels hypothesized by adult models of praxis processing. These models generally involve a conceptual system and a production system. Within this theoretical framework, the study analyzed the extent to which the gestural difficulties of children with DCD are related to a deficit of the production system. Considering the heterogeneity of deficits consistently reported in DCD, we also examined whether gestural difficulties of children with DCD could imply impairments on other cognitive functions (executive functions, visual-perceptual, and visuospatial functions). Thirty children with DCD were compared to 30 typically developing children. The DCD group exhibited a deficit in most of the gesture production tasks (with the exception of representational intransitive ones), with impaired visuospatial skills. When controlling for a measure of visuospatial skill, differences between groups remained significant only for representational transitive gestures. This dysfunction could neither be related to a semantic deficit, nor to an impairment of sensorimotor knowledge. Therefore, if the contribution of a visuospatial dysfunction allows discussing the specificity of gestural deficit, this does not appear to explain the overall gestural deficit. We suggest an explanation of the finding within the assumption of a production-system deficit.

Repeated apneas are associated with severe hypoxemia that may ultimately lead to loss of consciousness in some breath-hold divers. Despite increasing number of practitioners, the relationship between apnea-induced hypoxia and neurocognitive functions is still poorly understood in the sport of free diving. To shed light onto this phenomenon, we examined the impact of long-term breath-hold diving training on attentional processing, short-term memory, and long-term mnesic and executive functions. Thirty-six men matched for age, height, and weight were separated into the following 3 groups: (i) 12 elite breath-hold divers (EBHD), mean static apnea best time 371 s, 105 months mean apnea experience; (ii) 12 novice breath-hold divers, mean best time 243 s, 8.75 months mean apnea experience; and (iii) 12 physical education students with no breath-hold diving experience; all of these participants performed varied written and computerized neuropsychological tasks. Compared with the 2 other groups, the EBHD group was slower to complete the interference card during a Stroop test (F[1,33]= 4.70, p < 0.05), and presented more errors on the interference card (F[1,33]= 2.96, p < 0.05) and a lower total interference score (F[1,33]= 5.64, p < 0.05). The time to complete the interference card test was positively correlated with maximal static apnea duration (r = 0.73, p < 0.05) and the number of years of breath-hold diving training (r = 0.79, p < 0.001). These findings suggest that breath-hold diving training over several years may cause mild, but persistent, short-term memory impairments.

Computer use generally requires manual interaction with human-computer interfaces. In this experiment, we studied the influence of manual response preparation on co-occurring shifts of attention to information on a computer screen. The participants were to carry out a visual search task on a computer screen while simultaneously preparing to reach for either a proximal or distal switch on a horizontal device, with either their right or left hand. The response properties were not predictive of the target’s spatial position. The results mainly showed that the preparation of a manual response influenced visual search: (1) The visual target whose location was congruent with the goal of the prepared response was found faster; (2) the visual target whose location was congruent with the laterality of the response hand was found faster; (3) these effects have a cumulative influence on visual search performance; (4) the magnitude of the influence of the response goal on visual search is marginally negatively correlated with the rapidity of response execution. These results are discussed in the general framework of structural coupling between perception and motor planning.

It has been proposed that cognitive reserve is supported by two neural mechanisms: neural compensation and neural reserve. The purpose of this study was to test how these neural mechanisms are solicited in aging in the context of visual selective attention processing and whether they are inter- or intra-hemispheric. Younger and older participants were scanned using fMRI during a visual letter-matching task with two attentional load levels. The results show that in the low-load condition, the older participants activated frontal superior gyri bilaterally; these regions were not activated in the younger participants, in accordance with the compensation mechanism and the Posterior-Anterior Shift in Aging (PASA) phenomenon. However, when task demand increased, the older participants recruited the same regions (parietal) as the younger ones, showing the involvement of a similar neural reserve mechanism. This result suggests that successful cognitive aging relies on the concurrent use of both neural compensation and neural reserve in high-demand tasks, calling on the frontoparietal network. In addition, the finding of intra-hemispheric-based neurofunctional reorganization with a PASA phenomenon for all attentional load levels suggests that the PASA phenomenon is a function more of compensation than of reserve.

Resume Plusieurs travaux montrent des liens entre motricite et attention. Cette experience etudie dans quelle mesure l’analyse des specificites du controle moteur permet de predire les orientations attentionnelles. Pendant une recherche visuelle, les participants preparaient une sequence de deux pointages de cibles dont la direction et l’amplitude etaient manipulees. Ils devaient l’executer des qu’ils trouvaient la cible. Les espaces de reponse et de recherche visuelle etaient distincts. Les resultats montrent une influence de la sequence preparee sur les Temps de Reaction (TR) : (a) lorsqu’une sequence de deux pointages de petite amplitude est preparee, les deux gestes influencent les TR ; (b) lorsqu’une sequence de deux pointages de grande amplitude est preparee, seul le premier geste influence les TR. Ces resultats indiquent que quand le controle moteur de la sequence manuelle est majoritairement proactif, les deux composantes de la sequence influencent les orientations attentionnelles avant leur execution. Lorsque la part de controle en ligne du second geste augmente par rapport au controle proactif, seul le premier geste influence les orientations attentionnelles. Lors d’une preparation manuelle, les processus proactifs sont donc lies a ceux sous-jacents a l’orientation attentionnelle. Ces donnees sont interpretees dans la perspective de la theorie premotrice de l’attention.

The cognitive reserve hypothesis proposes that the brain actively attempts to cope with age-related changes by using pre-existing cognitive networks (neural reserve) or enlisting compensatory processes (neural compensation). In a context of visual selective attention, the current study compared task-related activation with BOLD fMRI signals in younger (N=16) and older (N=16) adults using a letter-name-matching task with two attentional load levels. In the low-load condition, the target letter might share the same identity (e.g., a/A) with one of two probes in the display, while in the high-load condition the display included four probes. The results suggest that there is an age-related change within the frontoparietal network that underlies visual selective attention processing. In the low-load condition, the older group needed to recruit more bilateral frontal regions to successfully perform the task, while the younger participants recruited more bilateral occipital regions, in agreement with the PASA (Posterior-Anterior Shift in Aging) phenomenon and the neural compensation hypothesis of cognitive reserve. In addition, in the high-load condition, we found a load-dependent posterior-anterior shift in the older participants, which was not present in the younger ones, involving the anterior part of the cingulate cortex. By showing a load-dependent PASA, our study indicates that the PASA phenomenon is supported more by the compensation mechanism (solicited exclusively in older participants) than by the reserve.

Plusieurs methodes de stimulation electrique ou magnetique du cerveau permettent d’etudier les relations entre sa structure et son fonctionnement, et les comportements ou les fonctions cognitives. Celles par stimulation directe, de surface ou profonde, sont reservees a des conditions pathologiques qui justifient l’application de la stimulation directement sur le cerveau. Dans un contexte ou une operation doit etre envisagee pour l’exerese d’une tumeur par exemple, il s’agit de determiner quelles sont les zones cerebrales qui doivent etre epargnees par la chirurgie, au risque sinon d’occasionner des troubles cognitifs, notamment du langage et de la memoire. Elles permettent dans le meme mouvement de recueillir des informations sur la cartographie cerebrale des mecanismes cognitifs et, au-dela, sur la connectivite au sein des reseaux cerebraux qui les sous-tendent. Les methodes dites non invasives sont principalement la stimulation magnetique transcrânienne et la stimulation par courant direct transcrânienne ; elles sont mises en œuvre aussi bien a des fins de recherche fondamentale qu’a des fins therapeutiques. Ce panorama introduit cinq articles issus des conferences accueillies par les 35es Journees de la Societe de neuropsychologie de langue francaise a l’universite de Nice-Sophia Antipolis, en mai 2011. Ils permettront d’approfondir les notions abordees ici, aussi bien du point de vue des contributions theoriques que cliniques.

What accounts for the Right Hemisphere (RH) functional superiority in visual change detection? An original task which combines one-shot and divided visual field paradigms allowed us to direct change information initially to the RH or the Left Hemisphere (LH) by deleting, respectively, an object included in the left or right half of a scene presented centrally. We manipulated the perceptual salience and semantic relevance of the change as well as the duration of the Inter-Stimulus Interval (ISI) between the scenes in order to clarify the role of the RH in memory and attention processes, and to explore whether lengthening the ISI would enhance the contribution of the LH. When analyzing data collapsed over the two levels (high vs. low) of salience and of relevance, changes were better detected in the left visual field (lvf) than in the right visual field (rvf) in the case of a short ISI, while no difference emerged in the case of a long ISI. Moreover, lengthening the ISI resulted in a performance decrement in the lvf, both for accuracy and response speed. The fact that the RH superiority was limited to short intervals indicates that stimulus-driven orienting contributes more than perceptual processing to this hemispheric asymmetry. When considering perceptual and semantic properties of the change, the effect of the ISI duration seemed to specifically emerge in the case of low relevance, with an enhancement of accuracy in the rvf when comparing the long with the short ISI. This suggests that the ISI influence on hemispheric performance operates on different levels.

Resume Cet article aborde la question des liens entre l’attention spatiale et la preparation motrice de gestes d’atteinte manuelle. Au cours d’une tâche de recherche visuelle, les participants se preparent a appuyer sur une des touches du pave numerique et executent ce geste des qu’ils ont detecte un intrus sur l’ecran. Le dispositif experimental permet de controler deux directions : celle de l’atteinte manuelle de la touche de reponse (dans le plan horizontal) et celle de l’orientation attentionnelle qui permet d’atteindre directement l’intrus a partir du point de fixation oculaire initial (dans le plan vertical). Les resultats montrent que : (a) lorsque ces deux directions sont congruentes les temps de reaction sont plus courts que lorsque ces deux directions sont incongruentes ; (b) cet effet est mis en evidence lorsque l’orientation de l’attention est controlee volontairement par le sujet, mais n’est pas significatif si l’intrus induit une capture attentionnelle automatique. Ces resultats suggerent que la recherche visuelle debute dans la direction qui est determinee par la preparation de l’atteinte manuelle. Ces resultats sont discutes dans le cadre de la theorie premotrice de l’attention.

L’interaction interhemispherique qui s’effectue principalement via le corps calleux represente un mecanisme flexible dont le role, dans la realisation d’une tâche, change de facon dynamique en fonction des demandes de traitement requis par la complexite de celle-ci. Cette capacite adaptative permet la distribution optimale entre les hemispheres des traitements de l’information relatifs a la tâche. Deux hypotheses concernant respectivement le vieillissement normal et la maladie d’Alzheimer sont considerees dans cette revue. A propos du vieillissement normal, il est suggere que cette flexibilite sous-tendrait les modifications de la lateralisation cerebrale recemment rapportees dans de nombreux travaux dans le domaine de la neuro-imagerie du vieillissement. En revanche, dans la maladie d’Alzheimer, le dysfonctionnement calleux ne permettrait pas l’accroissement du couplage interhemispherique qui serait requis pour compenser les pertes d’efficience des systemes monohemispheriques. Ainsi, dans la maladie d’Alzheimer, les mecanismes de reorganisation et de compensation permettant d’amoindrir les signes cliniques ne pourraient s’appuyer sur ceux qui semblent permettre un vieillissement cognitif reussi.

Resume Introduction Les troubles cognitifs ont longtemps ete peu etudies dans la sclerose en plaques (SEP), une des plus frequentes pathologies neurologiques de l’adulte jeune, et ce bien qu’ils puissent evoluer vers une demence fronto-sous-corticale et qu’ils soient presents chez plus de la moitie des patients. Meme si les potentiels evoques (PE) sensoriels sont classiquement utilises dans la SEP, les PE cognitifs ne sont pas proposes en clinique dans cette pathologie. Patients et methode Nous rapportons deux etudes visant a evaluer l’interet des PE cognitifs pour detecter precocement des troubles cognitifs dans la SEP. Tous les patients presentaient une SEP de type remittente depuis moins de 5 ans avec un handicap physique modere et exprimaient une plainte mnesique. Ils ont beneficie de tests neuropsychologiques et de l’enregistrement des PE lors du paradigme de l’ oddball , en modalites visuelle et auditive. Dans la premiere etude, 10 patients sans anomalie du bilan neuropsychologique ont ete inclus, 10 patients ayant une perturbation du bilan attentionnel et 10 sujets controles. Dix patients avec une perturbation du bilan mnesique et 10 controles ont participe a la seconde etude. Resultats Nos donnees sont en faveur d’une modification plus precoce des PE cognitifs dans la modalite visuelle qu’en auditif, avant meme la perturbation du bilan neuropsychologique. Dans les deux etudes, les parametres de la P300 etaient correles aux performances cognitives (attentionnelles dans la premiere etude et mnesiques dans la seconde) dans les deux modalites. Discussion Nos resultats montrent l’interet d’enregistrer les PE cognitifs non seulement en modalite auditive, mais aussi visuelle afin de rechercher des perturbations electrophysiologiques precoces alors meme que le bilan neuropsychologique n’est que peu contributif. Cette serie souligne l’apport clinique des PE cognitifs justifiant leur inclusion dans le bilan et le suivi de la SEP.

According to the hemispheric encoding/retrieval asymmetry (HERA) model, based on data obtained through functional neuroimaging, the left and right prefrontal cortices are preferentially, and, respectively, involved in long-term episodic memory encoding and retrieval. In this study, the HERA model was tested from a behavioral perspective using divided visual-field tachistoscopy. A recognition paradigm with both verbal and visuospatial materials was devised to differentiate memory-related effects (encoding vs. retrieval) from effects linked to the materials. The paradigm used lists of 12 and four items to assess long-term episodic memory and short-term memory, respectively. The aim of the latter condition was to test whether the HERA model is applicable in short-term memory. For long-term episodic memory, the data obtained validated the HERA model; the direction of the hemispheric asymmetry was found to depend on the type of materials used, whereas its magnitude was determined by the type of memory process. For verbal short-term memory, the HERA model seems to be confirmed. The pre-existing representations of the material could take into account the similarity of the hemispheric asymmetry pattern between short-term memory and long-term memory. In contrast, for visuospatial short-term memory, Baddeley's working memory model seems to better explain our results insofar as the asymmetries were essentially linked to the material in encoding but not in retrieval. This latter difference between short-term memory and long-term indicates that processes involved in LTM depend on episodic processes per se, hence, lending more support for the HERA model. Accordingly, these two memory systems seem to bring into play two different modes of hemisphere specialization.

Just like all the others specific learning disorders, dyspraxia is a key issue for public health and school performance. “Developmental dyspraxia” qualifies specific disturbances of gesture, i.e. the ability to produce a finalized action (goal-directed movement) and to use the objects [1] , [2] . Even if dyspraxia was described for decades, the value of the concept for diagnosis raises some debates in the international literature. Since 1994, a consensus has been established on the diagnostic entity of Developmental Coordination Disorder (DCD) to describe all children who exhibit developmental deficits of “motor coordination”. Beyond the usual debate of terminology, both the theoretical and the clinical definitions of the gestural dysfunctions in children remain insufficient in various respects. This communication provides a review of current controversies regarding the field of dyspraxia and DCD. Understanding the two entities of dyspraxia and DCD proves problematic, both when defining the concepts of praxis/motor coordination and when providing a theoretical analysis of the deficits they cover. More specifically, we aim at exploring the arguments supporting the hypothesis of a specific deficit in praxis development. We discuss the respective contributions of different impairment levels highlighted by studies of developmental gestural impairment (e.g. knowledge, executive functions, perceptive abilities…). Such a deconstruction of the concept of a specific deficit in praxis development argues in favor of an analysis that does not confuse gestural problems with other deficits made apparent through gesture.

We have recently shown that post-extinction retraining of rats, with a shock intensity that is too weak to induce by itself significant fear acquisition, impairs the recall of fear extinction memory. Tetanic stimulation (TS) of the medial prefrontal cortex (mPFC), applied before or following this retraining, facilitates extinction recall. Here we investigated whether mPFC TS can also facilitate expression of fear extinction when rats are retrained with the same shock intensity as during the initial fear acquisition. Rats were implanted with stimulating electrodes in the mPFC and were trained to acquire freezing to a conditioning chamber, in which they had to enter freely. In Experiment 1, extinction of this response was followed by reconditioning and then another extinction training. Acquired freezing was extinguished successfully, while reacquired freezing, which was associated with increased chamber entry latencies, was resistant to subsequent extinction. Both reacquired freezing and increased chamber entry latencies were absent in rats that received post-reconditioning mPFC TS. In Experiment 2, post-conditioning mPFC TS had no effect on initially acquired freezing. In Experiment 3, rats were submitted to reconditioning without experiencing extinction training. In this condition, both reacquired freezing and increased chamber entry latencies were still present in rats that received post-reconditioning mPFC TS. These findings provide additional evidence for the fundamental role of the mPFC in maintaining expression of fear extinction.

International audience; This paper provides a review of current knowledge in the field of specific motor coordination and gestural disorders in children, generally referred as two major diagnosis: developmental dyspraxia and Developmental Coordination Disorder (DCD). After few reminders of the main notions, we analyse the controversies regarding the distinction of dyspraxia and DCD. The specificity of dyspraxia’s subtypes is discussed regarding the heterogeneity of deficits and their interpretation. This leads us to propose theoretical and clinical perspectives for a complete assessment enabling to identify all praxic variables contributing to dyspraxia. A better understanding of the nature of praxic disorders reported in children is needed to overcome current limitations, in order to identify the evidence of specific mechanisms and etiology of developmental dyspraxia.; Cet article propose une synthèse des connaissances sur les troubles spécifiques de la motricité et du geste chez l’enfant, généralement qualifiés selon deux étiquettes diagnostiques: la dyspraxie développementale et le trouble de l’acquisition de la coordination (TAC). Après un bref rappel des principales notions, les controverses relatives à la différenciation de la dyspraxie et du TAC sont exposées: cette section met en exergue les impasses conceptuelles qui limitent l’avancée des connaissances dans le domaine. La spécificité des différents sous-types de dyspraxie est ensuite discutée en regard de l’hétérogénéité des perturbations et des divergences quant à leur interprétation. À l’issue de cette revue, sont envisagées les perspectives pour un examen exhaustif et théoriquement guidé des différents types de troubles praxiques décrits en neuropsychologie clinique de l’enfant. La démarche épistémologique proposée se justifie par la nécessité d’interroger la pertinence des découpages théoriques et fonctionnels opérés, et au-delà, l’existence d’une authentique dyspraxie développementale.

OBJECTIVE Alzheimer's disease (AD) is a progressive neurodegenerative disorder that affects the corpus callosum (CC), which plays a key role in interhemispheric coupling in high-demand conditions. Using 3D callosal measurements and a letter-matching paradigm, this 2-part study investigated the neural substrate of interhemispheric coupling in individuals with AD or amnestic mild cognitive impairment (a-MCI) and age-matched healthy individuals (HC). METHOD Thirty-three right-handed participants were MRI scanned to measure the volume of the CC in 5 sections. In Study 1, AD, a-MCI, and HC individuals performed a low-demand perceptual letter shape-matching task (e.g., A-A); in Study 2, a-MCI and HC individuals performed a "case-sensitive" letter-matching task (Study 2A) and a "load-sensitive" letter-matching task (Study 2B). RESULTS The results showed a positive correlation between Response Times and the midbody of the CC at the lowest cognitive demand level (Study 1) in participants with AD, and the total CC, midbody, caudal body, and isthmus of the CC at high cognitive demand levels (Study 2A) in normal aging. The volume of the anterior part of the CC was significantly negatively correlated with the interhemispheric behavioral indices for the a-MCI group (Study 1 and Study 2B). CONCLUSION This study provides evidence that interhemispheric coupling may constitute a flexible mechanism that can improve the brain's ability to meet processing demands for low cognitive demand in AD and for high cognitive demand in normal aging.

In a one-shot change detection task, we investigated the relationship between semantic properties (high consistency, i.e., diagnosticity, versus inconsistency with regard to gist) and perceptual properties (high versus low salience) of objects in guiding attention in visual scenes and in constructing scene representations. To produce the change an object was added or deleted in either the right or left half of coloured drawings of daily-life events. Diagnostic object deletions were more accurately detected than inconsistent ones, indicating rapid inclusion into early scene representation for the most predictable objects. Detection was faster and more accurate for high salience than for low salience changes. An advantage was found for diagnostic object changes in the high salience condition, although it was limited to additions when considering response speed. For inconsistent objects of high salience, deletions were detected faster than additions. These findings may indicate that objects are primarily selected on a perceptual basis with subsequent and supplementary effect of semantic consistency, in the sense of facilitation due to object diagnosticity or lengthening of processing time due to inconsistency.

The perceptual salience and semantic relevance of objects for the meaning of a scene were evaluated with multiple criteria and then manipulated in a change-detection experiment that used an original combination of one-shot and tachistoscopic divided-visual-field paradigms to study behavioural hemispheric asymmetry. Coloured drawings that depicted meaningful situations were presented centrally and very briefly (120 ms) and only the changes were lateralised by adding an object in the right or in the left visual hemifield. High salience and high relevance improved both response times (RTs) and accuracy, although the overall contribution of salience was greater than that of relevance. Moreover, only for low-salience changes did relevance affect speed. RTs were shorter when a change occurred in the left visual hemifield, suggesting a right-hemisphere advantage for detection of visual change. Also, men responded faster than women. The theoretical and methodological implications are discussed.

International audience

International audience; Several studies in Functional Magnetic Resonance Imaging done among elderly people have revealed a bilateral activation, which correlated with higher performance among elderly adults. Cabeza posited the HAROLD model (i.e., Hemispheric Asymmetry Reduc- tion in Older Adults, HAROLD) to account for this effect: compared to younger adults, brain activity among elderly people tends to be less lateralized. The aim of this work is to focus on the nature of the inter-hemispheric mechanisms among elderly adults by studying the sharing of processing efficiency between the two hemispheres. It is assumed that the age-related hemispheric asymmetry reductions result from the emergence of an inter-hemispheric compensa- tion mechanism that expresses a modification of the distribution of the exchanges between the two hemi- spheres. Thus, the elderly appear to take advantage of a bi-hemispheric processing even for the most simple tasks. Twenty participants (10 young and 10 elderly adults) were submitted to a letter-matching task under a divided visual field tachistoscopic presentation. The main results show an early shift in efficiency from within- to across-hemisphere processing with aging. Young adults showed an across-hemisphere advantage only for the most complex task. In contrast, older adults showed an across-hemisphere advantage at all levels of task complexity for accuracy and latency data. The benefits associated with greater computational power outweigh the costs of integrating process- ing between the hemispheres in elderly adults. In conclusion, inter-hemispheric interactions may consti- tute a flexible mechanism that can improve the brain’s ability and thus may compensate for neural decline that accompanies normal aging.