Nathalie Agar

Hôpital Raymond-Poincaré – Hôpitaux universitaires Paris Ile-de-France Ouest, Île-de-France, France

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Publications (16)25.46 Total impact

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    ABSTRACT: Conway's autobiographical memory (AM) model postulates that memories are not stored in a crystallised form in long-term memory but are reconstructed at time of retrieval via executive and binding processes, to create a temporary multimodal representation from different AM knowledge. Traumatic brain injury (TBI) impairs AM recollection. However, no study has yet considered the distinct roles of executive and short-term feature-binding functions in the retrieval deficits of retrograde AMs after TBI. Examining a group of 33 TBI patients and 33 controls, our study addresses these roles through a first-ever exploration of the links between performance on an AM verbal fluency evaluation that distinguishes four levels of representation, from semantic to episodic (lifetime periods, general events, specific events, specific details of a specific event), and three executive functions (shifting, inhibition and updating) and two short-term feature-binding functions (short-term formation and maintenance of multimodal representations). The results showed that TBI patients were impaired compared to controls in the retrieval of both semantic and episodic retrograde AM representations, but especially for the most episodic level of AM, in the three executive functions and the short-term maintenance of multimodal representations. Regression analyses indicated that the executive predictors (mainly updating) mediated a large proportion (over 70%) of TBI-related deficit on the retrieval of lifetime periods, general events and specific events, in contrast with the main impairment on generation of specific details which were only mildly (just 12%) predicted by the short-term maintenance of multimodal representations. Additional analyses in a subgroup of patients point to episodic memory abilities and time since injury in predicting the retrieval of specific events and details. In summary, the present study mainly emphasizes that the executive deficits in TBI are involved in the disruption of the first levels of AM generative processes that give access to the multiple episodic details recollection.
    Cortex 01/2011; 47(7):771-86. · 6.16 Impact Factor
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    ABSTRACT: We will start with very general events that lasted a long time, and then go on to very specific and detailed events corresponding to very short moments of your life, like a zoom. Note carefully! This is a four-stage task: at each stage, you will be given a limited time to list events. Try to create response lists according to the criterion given. When the time is up, we will go through each item you listed, and ask for more information. For each stage, I will give you examples. 1. VAF1: In our life, there are periods that last several years; they have a (very) long duration. Examples: The lifetime period of "primary school," the lifetime period of "living on Blue Street," the lifetime period of "living with Paul," the lifetime period of "the first job," etc. -Can you remember any periods of your life that lasted several years (at least 3 years)? -These periods can overlap (examples: The period "living on Blue Street" overlaps the periods "going to high school" and "going to university") -You have two minutes to give me as many lifetime periods as you can. 2. VAF2: During any given period, there are things we do regularly. Examples: For example, if I choose the period "living on Blue Street": dance lessons, country weekends, family Christmas, parties with high school friends, etc. There are also things that last a relatively long time (several days, several weeks), but that have shorter duration than periods of life. Examples: For example, if I choose the period "living on Blue Street": holidays in Italy, pottery courses, seasonal jobs during the grape harvest, etc.
    Cortex 01/2011; supplementary material. · 6.16 Impact Factor
  • Cortex 01/2011; · 6.16 Impact Factor
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    ABSTRACT: Although fatigue is one of the most frequent complaints of individuals with traumatic brain injury (TBI), its mechanisms remain poorly understood. The objective of this study was to assess the relationships between subjective mental fatigue, mental effort, attention deficits, and mood after severe TBI. and participants. A total of 27 patients with subacute/chronic severe TBI were compared with matched controls. Patients first rated their baseline subjective fatigue on the Fatigue Severity Scale (FSS) and on the Visual Analog Scale for Fatigue (VAS-F). Mood was assessed with the Montgomery and Asberg Depression Rating Scale (MADRS). Then, they performed a long-duration selective attention task, separated in 2 parts. Fatigue on the VAS-F was assessed again between the 2 parts and at the end of the attention task. Patients were also asked to rate on the VAS the level of subjective mental effort devoted to the task. Patients reported a higher baseline fatigue than controls. They performed significantly poorer on the selective attention task. Significant correlations were found in the group with TBI between attention performance, mental effort, and subjective fatigue. Depression did not significantly correlate with fatigue. These findings suggest that patients with more severe attention deficits have to produce higher levels of mental effort to manage a complex task, which may increase subjective fatigue, in line with the coping hypothesis.
    Neurorehabilitation and neural repair 08/2009; 23(9):939-44. · 4.28 Impact Factor
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    ABSTRACT: Introduction Le traumatisme crânien (TC) entraîne des troubles de récupération en mémoire autobiographique (MA). Le modèle de Conway propose une reconstruction contrôlée des souvenirs grâce à trois types de représentations. Objectifs Notre recherche examine les mécanismes entraînant des déficits en MA chez des patients TC sévères en étudiant les relations entre la MA, la mémoire de travail (MT) et les fonctions exécutives. Méthodes 16 patients TC et 22 contrôles réalisèrent une tâche originale qui reproduit le processus de récupération du modèle de Conway grâce à des fluences verbales autobiographiques (FVA) qui ciblent les périodes de vie (FVA1), les événements généraux (FVA2), les événements spécifiques (FVA3) et les détails perceptivo-sensoriels (FVA4). Une batterie de tests fut utilisée pour évaluer la MT, les fonctions exécutives (mise à jour, inhibition et flexibilité) et la vitesse de traitement (VT). Résultats Les ANOVA montrèrent que les patients fournissent moins de réponses pour les FVA1, 2 et 3 et sont moins performants pour les empans visuels, le buffer épisodique, la mise à jour et la VT. Les résultats des analyses de régression pas à pas indiquèrent que le buffer épisodique et la VT prédisaient 21,5 p. 100 de la FVA2. L’inhibition et la VT prédisaient 31,5 p. 100 de la FVA3. La flexibilité rendait compte de 8,3 p. 100 de la FVA4. Discussion Ces résultats confirment l’impact d’un dysfonctionnement exécutif sur les troubles de récupération en MA après un TC. Ils permettent également de mettre en avant une implication préférentielle des processus de la MT au niveau de la récupération des événements généraux et spécifiques, alors qu’ils semblent moins impliqués dans la récupération de détails perceptivo-sensoriels. Conclusion Cette étude met en lumière le rôle du buffer épisodique, qui permet la récupération de souvenirs en liant des informations de différentes sources et modalités dans un format accessible à la conscience.
    Revue Neurologique - REV NEUROL. 01/2007; 163(4):59-59.
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    ABSTRACT: Fatigue is frequent and disabling in patients with traumatic brain injury (TBI). Its mechanisms are complex and multifactorial. We performed a literature review of reports of the condition using the following key words: brain injury, depression, neuroendocrine dysfunction, and treatment. Five scales have been used to evaluate fatigue in TBI patients: the Fatigue Severity Scale, the visual analog scale (VAS) for fatigue, the Fatigue Impact Scale, the Barrow Neurological Institute (BNI) Fatigue Scale and the Cause of Fatigue (COF) Questionnaire. The BNI Fatigue Scale and the COF Questionnaire have been designed specifically for brain-injured patients. Fatigue is present in 43-73% of patients and is one of the first symptoms for 7% of them. Fatigue does not seem to be significantly related to injury severity not to time since injury. It can be related to mental effort necessary to overcome attention deficit and slowed processing ("coping hypothesis"). It can also be related to sleeping disorders and depression, although the relation between fatigue and depression are debated. Finally, fatigue can also be related to infraclinical pituitary insufficiency (growth hormone insufficiency, hypocorticism). To date, no published study of treatment of fatigue after TBI exists.
    Annales de Réadaptation et de Médecine Physique 08/2006; 49(6):283-8, 370-4.
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    ABSTRACT: Fatigue is frequent and disabling in patients with traumatic brain injury (TBI). Its mechanisms are complex and multifactorial. We performed a literature review of reports of the condition using the following key words: brain injury, depression, neuroendocrine dysfunction, and treatment. Five scales have been used to evaluate fatigue in TBI patients: the Fatigue Severity Scale, the visual analog scale (VAS) for fatigue, the Fatigue Impact Scale, the Barrow Neurological Institute (BNI) Fatigue Scale and the Cause of Fatigue (COF) Questionnaire. The BNI Fatigue Scale and the COF Questionnaire have been designed specifically for brain-injured patients. Fatigue is present in 43–73% of patients and is one of the first symptoms for 7% of them. Fatigue does not seem to be significantly related to injury severity not to time since injury. It can be related to mental effort necessary to overcome attention deficit and slowed processing (“coping hypothesis”). It can also be related to sleeping disorders and depression, although the relation between fatigue and depression are debated. Finally, fatigue can also be related to infraclinical pituitary insufficiency (growth hormone insufficiency, hypocorticism). To date, no published study of treatment of fatigue after TBI exists.
    Annales de Réadaptation et de Médecine Physique. 07/2006;
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    ABSTRACT: La fatigue est une plainte fréquente et invalidante après un traumatisme crânien. Ses origines sont multifactorielles et intriquées. Nous avons effectué une revue de la littérature en utilisant les mots clés : fatigue, brain injury, depression, neuroendocrine dysfunction, treatment. Nous avons relevé cinq échelles utilisées dans différentes études pour évaluer la fatigue (Fatigue Severity Scale, Echelle Visuelle Analogique-Fatigue, Fatigue Impact Scale, Barrow Neurological Institute Fatigue Scale, et Cause Of Fatigue Questionnaire) dont les deux dernières ont été mises au point spécifiquement chez des traumatisés crâniens. La fatigue touche, en fonction des études, 43 à 73 % des patients et est ressentie comme un des premiers symptômes par 7 % d'entre eux. Elle est induite par les efforts nécessaires pour maintenir un bon niveau de performance malgré les déficits cognitifs et la lenteur (hypothèse du « coping »). Les troubles du sommeil fréquemment présents et la dépression peuvent également favoriser son apparition, cependant les liens entre fatigue et dépression sont beaucoup plus controversés que dans d'autres pathologies telles que la sclérose en plaques et l'hémiplégie. Elle peut également être causée par une insuffisance infraclinique de l'axe hypothalamohypophysaire (déficit en hormone de croissance, l'hypocorticisme). Aucune étude n'a étudié un éventuel traitement mais il paraît souhaitable de proposer une prise en charge de ce trouble.
    Annals of Physical and Rehabilitation Medicine. 01/2006; 49(6):283-288.
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    ABSTRACT: Severe diffuse traumatic brain injury (TBI) may impair the performance of daily-life complex activities. The aim of the present study was to assess whether these difficulties are related to a representational impairment of action knowledge. Two tasks requiring the manipulation of scripts were used. The first (script reconstitution) required subjects to sort cards describing actions belonging to 4 different scripts, presented in a random order. The second (script generation) required subjects to generate actions belonging to a given script. The results showed that TBI patients had preserved access to goal representation and action knowledge. However, they demonstrated (1) significant impairments when they had to deal with simultaneous competing sources of information and (2) a lack of inhibitory control on routine overlearned skills. Patients' performance was significantly correlated with behavioral modifications in everyday life. These data suggest that action impairment in severe TBI patients cannot be attributed to an impairment of action knowledge per se. As previously suggested by Schwartz et al., a restriction of limited-capacity processing resources may account for the observed deficits.
    Journal of the International Neuropsychological Society 12/2001; 7(7):795-804. · 2.70 Impact Factor
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    Annales de Réadaptation et de Médecine Physique. 40(6).
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    Annales de Réadaptation et de Médecine Physique. 41(6).

Publication Stats

56 Citations
25.46 Total Impact Points

Institutions

  • 2007
    • Hôpital Raymond-Poincaré – Hôpitaux universitaires Paris Ile-de-France Ouest
      Île-de-France, France
  • 2006
    • Université de Versailles Saint-Quentin
      Versailles, Île-de-France, France