The current research project examines the performance of a group of high functioning young adult males with autism spectrum disorders on standardized measures of neurocognitive functioning to determine whether distinct cognitive profiles of strengths and weaknesses emerge. Neuropsychological test data across various domains: general cognitive ability, visuospatial processing, verbal learning and memory, visual learning and memory, working memory, reasoning, cognitive flexibility, attention, receptive language, expressive language, social and emotional processing, and fine motor skills was examined. Data were analyzed using cluster analysis to assess for the presence and nature of unique clusters/subgroups based on neuropsychological test performance. Three unique clusters were derived from the analyses. This study highlights the well-documented heterogeneity across the spectrum of autism and suggests a method for parsing a heterogeneous sample of ASD subjects into smaller and more meaningful homogeneous groups using standardized neuropsychological assessments. / text

Made available in DSpace on 2016-12-08T16:35:06Z (GMT). No. of bitstreams: 1 116957.pdf: 3044636 bytes, checksum: 18170911eadbb2642a45564d00a413bd (MD5) Previous issue date: 2014-03-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The use of Digital Technologies of Information and Communication (DTIC), specifically of the hypermedia, is constantly changing the way people work, play and also organize their thinking. In this way DTIC changes our way of think and behave (SANTAELLA, 2004; LÉVY, 1993; CASTELLS, 2000). For many children born surrounded by these technologies and is now attending Basic Education, hypermedia is part of their everyday life and the computer is more than a toy used for leisure, they use to interact with friends and seek information. These children are developing another ways to learn and have shown different cognitive profiles from those of previous generations. They already navigate in the cyberspace easily, even before starting the process of formal literacy. This dissertation examined the navigation routes in cyberspace of children attending the first grade of Basic Education that are experiencing the first stage of literacy. The qualitative research was characterized as a Case Study (YIN, 2005; GIL, 2009). The research subjects were the 25 children attending the first year of the Basic Education Intendente Aricomedes da Silva (EBIAS), located in Florianópolis/SC, Brazil. The study conducted analysis of three types of data collected through participant observation, pedagogical interventions and semi structured collective interview. Among the authors who are dialogued are Lucia Santaella (2004, 2008), Pierre Lévy (1993, 1999), Lucia Leão (2002, 2005), Magda Soares (2002), Carla Viana Coscarelli (2006, 2011), Leni Vieira Dornelles (2005), David Buckingham (2007). We identify the main routes and navigation in cyberspace according to the types of users: beginner, layperson and expert, defined by Santaella (2004). The navigation routes of the children of the first grade were based on the reading of images and symbols of cyberspace, discovering the browser commands and hypermedia. The routes happened through choices grounded in their previous knowledge or through actions of the type trying and error. The children had memorized specific routes and shared with the classmates, these routes were usually initiated by a research in the search box of the browser. We also see a significant relationship between the use of hypermedia and the process of formal literacy, literacies and digital literacy, as processes that take place in the same time and influence each other. / O uso das TDIC, especialmente das hipermídias, vem modificando a forma como as pessoas se relacionam, trabalham, se divertem e também organizam o seu pensamento. Assim as TDIC alteram a nossa forma de pensar e agir (SANTAELLA, 2004; LÉVY, 1993; CASTELLS, 2000). Para muitas crianças que nasceram cercadas por estas tecnologias e hoje frequentam o Ensino Fundamental, as hipermídias fazem parte do seu cotidiano e o computador é mais um brinquedo que usam para o lazer, para interagir com os amigos e buscar informações. Estas crianças estão desenvolvendo diferentes formas de aprender e vêm apresentando perfis cognitivos diferentes dos das gerações anteriores. Elas navegam no ciberespaço com facilidade, antes mesmo de iniciarem seu processo de alfabetização formal. Esta dissertação analisou como se desenvolvem as rotas de navegação no ciberespaço de crianças que frequentavam o primeiro ano do Ensino Fundamental e estão vivenciando a alfabetização escolar. A pesquisa de natureza qualitativa se caracterizou como um estudo de caso (YIN, 2005; GIL, 2009). Os sujeitos da pesquisa foram 25 crianças que frequentavam o primeiro ano do Ensino Fundamental de uma escola municipal, localizada em Florianópolis/SC. O estudo realizou análise de três tipos de dados coletados por meio de observação participante, intervenções pedagógicas e entrevista coletiva semiestruturada. Dentre os autores que dialogamos estão: Lucia Santaella (2004, 2008), Pierre Lévy (1993, 1999), Lúcia Leão (2002, 2005), Magda Soares (2002), Carla Viana Coscarelli (2006, 2011), Leni Vieira Dornelles (2005), David Buckingham (2007). Identificamos as rotas e as principais características de navegação no ciberespaço de acordo com os tipos de usuários: novato, leigo e experto, definidos por Santaella (2004). As rotas de navegação das crianças do primeiro ano eram fundamentadas na leitura de imagens e de símbolos do ciberespaço, na descoberta dos comandos do navegador e das hipermídias. As rotas ocorriam por meio de escolhas alicerçadas em seus conhecimentos prévios ou por meio de ações do tipo tentativa e erro. As crianças memorizaram rotas específicas e compartilhavam com os colegas de turma, normalmente estas eram iniciadas por uma pesquisa no campo de busca do navegador. Percebemos ainda uma relação significativa entre o uso das hipermídias e o processo de alfabetização formal, letramento e letramento digital, como processos que ocorrem paralelamente e se influenciam mutuamente.

Made available in DSpace on 2016-03-15T19:40:42Z (GMT). No. of bitstreams: 1 Cintia Perez Duarte.pdf: 1965933 bytes, checksum: b913710fccf97a365f6a4ab6112b18cd (MD5) Previous issue date: 2009-08-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Working memory is assumed to be a limited capacity responsible for maintaining and manipulating information for a short period of time, that are underpins the capacity for complex thought and learning. People with Down Syndrome have a deficit in their working memory and in general, they can t maintain information for a short period of time and this can result in learning difficulties, language development and complexes thoughts. The aim of Study 1 was to characterize cognitive profile of people with Down Syndrome, they were aged between 6 and 45 years old (M=16,64, SD=9,955), using WISC-III, WAIS-III, TVIP, Token-Comp and FAS-Animals and Fruits tests. The results appointed a cognitive performance under the average, however with significantly differences between verbal IQ and execution IQ which showed a better performance. There was a trend observed in their development and enlargement of their receptive vocabulary related to their ages, nevertheless the same doesn t happen with verbal fluency. The words follow by semantic processing were more recovered than those through the phonological processing. Most of them can organize concepts and semantics categories, however they don t have control of phonologic and structural aspects of the words. They also have difficulties to maintain and manipulate verbal information. The Study 2 compare performance of people with Down Syndrome, they were aged between 6 and 16 years old (M=10,36, SD=3,451) and the control group defined according to WISC-III test scores, using tests that evaluated receptive vocabulary, verbal and visual-spatial short term memory. This comparison was made through the TVIP, Digit Span direct and reverse order, Corsi direct and reverse order and some working memory tests created for this study. The results appointed no significant difference between the majority of the tests averages, excluding Digit Span direct order, considering that the group without syndrome had a higher performance compared to Syndrome group. Considering the direct and reverse orders in Digi Span and Corsi, intra-groups performances was compared which demonstrated significantly differences of the both groups. In general, results of both studies confirm the literature, that describe the heterogeneity of the Down Syndrome cognitive profile and appoint to evidences of strong non verbal abilities, often less impaired than linguistics abilities. / A memória de trabalho é caracterizada por ser um sistema de capacidade limitada responsável por manter e manipular informações por um curto período de tempo, que são subjacentes à capacidade de pensamento complexo e aprendizado. Pessoas com síndrome de Down apresentam prejuízos referentes à memória de trabalho e, em geral, não conseguem manter informações em um curto período de tempo, o que pode levar a dificuldades no aprendizado, desenvolvimento de linguagem e pensamentos complexos. O Estudo 1 teve como objetivo caracterizar o perfil cognitivo de pessoas com síndrome de Down, com idades entre 6 e 45 nos (M=16,64, DP=9,9555), por meio dos testes WISC-III, WAIS-III, TVIP, Token-Comp e FAS-Animais e Frutas. Resultados indicaram funcionamento cognitivo abaixo da média, porém com diferença significativa entre QI verbal e QI execução, com melhor desempenho referente ao QI de execução. Notou-se uma tendência no desenvolvimento e ampliação de vocabulário receptivo com avanço da idade, mas o mesmo não ocorre com a fluência verbal. As palavras acompanhadas de processamento semântico foram mais evocadas do que o fonológico, ou seja, a maioria possui organização de conceitos e classes semânticas, mas não têm domínio dos aspectos fonológicos e estruturais das palavras. Também apresentaram dificuldade para manter e manipular informações verbais. O Estudo 2 comparou o desempenho de pessoas com síndrome de Down, com idades entre 6 e 16 anos (M=10,36, DP=3,451) e controles pareados pela pontuação bruta do WISC-III, em provas que avaliaram vocabulário receptivo e memória de curto prazo verbal e visuo-espacial por meio dos testes TVIP, Dígitos ordem direta e inversa, Corsi ordem direta e inversa, e provas de memória de trabalho desenvolvidas para este estudo. Resultados indicaram que não houve diferença significativa entre as médias para a maioria das provas, com exceção de Dígitos ordem direta, sendo que o desempenho do grupo sem a síndrome foi superior ao grupo com a síndrome. Comparações do desempenho intra grupos, considerando-se a ordem direta e inversa das provas Dígitos e Corsi, indicaram diferenças significativas para ambos os grupos. Em geral, os dados dos dois estudos corroboram com a literatura, que descreve a heterogeneidade do perfil cognitivo de pessoas com síndrome de Down e apontam para evidências quanto a força de habilidades não verbais, geralmente menos afetadas do que habilidades lingüísticas.

Made available in DSpace on 2016-03-15T19:40:29Z (GMT). No. of bitstreams: 1 Maria Luiza Mesquita.pdf: 1339144 bytes, checksum: 96e23145c62c671a2f420c67daa9ed7f (MD5) Previous issue date: 2008-02-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Prader Willi syndrome is a genetic disorder caused by the absence of the paternally derived PWS region of chromosome 15. Some patognomonics symptoms of this disorder are hyperphagia and obesity, which in most cases happens before the age of six and they severely harm the quality of life of such patients. The present study has focused on the behavioral area and aimed at identifying the daily frequency of eating habits and the caloric intake of children with PWS; identifying the variables of family interaction which control the eating behavior and tracing a cognitive and behavioral profile of the PWS patients. The sample was made by eleven children with a PWS genetic diagnosis, between the ages of 7 and 16 and their parents. The data collecting instruments were: a questionnaire for the eating habits record of the children, an interview to identify controlled environment variances of the eating behavior and the Brazilian version of the Child Behavior Checklist for ages 6-18 (CBCL/6-18) by Achenbach and the WISC-III test (Wechsler Intelligence Scale for Children- 3 rd edition). The data went through an evaluation which included topographic record and functional analysis of eating behavior and others types of children´s non- adaptive behaviors and analyses and comparison of frequency distribution of these behaviors in relation to cognitive and behavioral profiles of the patients. The group was characterized as obese according to the BMI calculation. The main results showed that 82% from the total classified in the WISC-III test as mentally retarded, 100% of the sample was at clinic level and in at lest one of the syndrome scales, competences or problems of the instrument CBCL/6-18. One of the high frequency behavioral classes was the negotiations to obtain food from their parents. There is a behavioral chart configured as pathological in terms of response for tantrums, manipulation, aggressiveness, breaking of rules and oppositionist behavior. Psychiatric comorbidity has also been identified, associated to high consumption of psychotropic drugs. / A Síndrome de Prader Willi (SPW) é uma doença genética de origem paterna causada pela perda de expressão de genes no cromossomo 15. Alguns sintomas patognomônicos da doença são a hiperfagia e a obesidade que, na maioria dos casos, ocorre antes dos seis anos e compromete severamente a qualidade vida desses pacientes. O presente estudo se concentrou na área comportamental e teve como objetivos: - identificar a freqüência diária de comportamentos alimentares e ingestão calórica de crianças com SPW; - identificar as variáveis de interação familiar que controlam os comportamentos alimentares e; - traçar um perfil comportamental e cognitivo dos sujeitos com SPW. A amostra foi composta por onze crianças com diagnóstico genético de SPW, na faixa etária de 7 a 16 anos e seus pais. Os instrumentos de coleta de dados foram: um questionário para o registro de hábitos alimentares da criança, uma entrevista para identificar variáveis ambientais controladoras dos comportamentos alimentares, a versão brasileira do Child Behavior Checklist for ages 6-18 (CBCL/6-18) de Achenbach e o Teste WISC-III (Escala de Inteligência Wechsler para crianças 3ª edição). Os dados passaram por uma avaliação que incluiu um registro topográfico e análise funcional de comportamentos alimentares e de outros tipos de comportamentos desadaptativos das crianças e análise e comparação das distribuições de freqüências desses comportamentos em relação aos perfis cognitivo e comportamental dos sujeitos. O grupo foi caracterizado como obeso de acordo com o cálculo do IMC. Os principais resultados apontaram que 82% do total classificaram-se no teste WISC-III como débil mental, 100% da amostra pontuaram na faixa clínica em, pelo menos uma das escalas das síndromes, competências ou problemas do instrumento CBCL/6-18. Uma das classes comportamentais de alta freqüência foram as negociações para obter alimentos dos pais. Há um quadro comportamental configurado como patológico em termos de respostas de birra, manipulação, agressividade, quebrar regras e oposicionismo. A comorbidade psiquiátrica também foi identificada, inclusive associada a um consumo elevado de psicotrópicos.

La réalité virtuelle (RV) va révolutionner de nombreux domaines comme le domaine médical, industriel, architectural, etc. C'est devenu un élément important dans la phase de développement d'une solution, notamment dans le domaine architectural. Que ce soit pour la commercialisation ou la revue de projet, la RV permet de faire des visites virtuelles de maisons visualisées à l'échelle réelle en environnement virtuel (EV). Aujourd'hui, l'architecte dispose d'un véritable outil de commercialisation en proposant aux acheteurs potentiels des visites virtuelles de maisons. Lors de ces visites virtuelles, le client peut avoir une idée de la maison. Avec la visualisation à l'échelle 1:1 le client a la possibilité d'explorer la maison et peut ainsi se projeter plus facilement dans la maison pour prendre plus facilement des décisions. L'espoir est que cette visite virtuelle puisse conduire plus rapidement à une signature de précontrat. Par ailleurs, lors du processus de conception, l'architecte peut effectuer une revue de projet en EV avec le client afin de le guider dans ses choix et d'affiner le recueil des besoins. À l'issue de cette revue, ensemble, ils valident le plan de la maison en termes de taille et d'agencement des pièces, de position des fenêtres, etc. Par conséquent, la RV permet un gain de temps et d'argent considérable aux architectes. Les décisions prises en EV sont généralement basées sur la perception des distances et des volumes. Par conséquent, l’efficacité des décisions prises dépend de la capacité des visiteurs à porter un jugement sans biais sur ce qu’ils voient dans l’EV par rapport à l’environnement réel correspondant. Plusieurs études ont montré que l'estimation des distances en EV est différente de l'estimation en environnement réel. De multiples facteurs peuvent être à l'origine de ce problème, comme le dispositif d'affichage, le champ de vision restreint, la qualité graphique, etc. Malgré les différentes études consacrées à cette problématique, les causes de ce phénomène restent diverses et mal identifiées. Notre travail s'inscrit dans le cadre d'un projet architectural : le projet CIMBEES. Ce projet vise à intégrer la RV dans le processus de vente/achat et de conception au travers de la visite virtuelle et de la revue de projet en EV. Notre travail consiste à concevoir et à évaluer l'outil de revue de projet architectural en EV. La phase de conception consiste à proposer un outil de revue de projet permettant la visualisation des maquettes numériques à l'échelle réelle et offrant une interaction qui répond aux besoins des architectes. Au cours de cette phase nous avons développé un outil de revue de projet et nous avons modélisé les maquettes numériques nécessaires à partir de plans réels de maison.Dans la phase d'évaluation de l'outil de revue de projet architectural, nous nous sommes intéressés à la problématique de la perception des distances en EV. L'objectif de cette évaluation est d'identifier et d'étudier les facteurs les plus importants pour l'outil afin de proposer des paramètres adaptés à notre contexte applicatif (les visites virtuelles). Pour ce faire, nous avons effectué une étude expérimentale qui porte sur l'étude de l'influence de trois facteurs sur la perception des distances : 1) le profil cognitif des utilisateurs, 2) le contexte environnemental et 3) la vitesse de navigation [...] / Virtual reality (VR) will revolutionize many fields such as medicine, industry, architecture, etc. It has become an important element in the development of a solution, particularly in the architectural field. Whether for marketing or project review, VR allows virtual visits of homes in virtual environment (VE) at real scale. Today, the architect has a real marketing tool by providing to potential customer virtual visits of homes. During these virtual visits, the customer can get an idea of the house. With the visualization at scale 1: 1, the customer has the opportunity to explore the house and he can easier project himself into the house to take decisions more easily. The hope is that, this virtual visit would more quickly lead to a signing agreement.Furthermore, during the design process, the architect can make a project review in VE with customer to guide his choices and refine the collection of needs. Following this review, together, they validate the plan of the house in terms of size and layout of rooms, window position, etc. Therefore, the VR allows considerable time and money saving for architects. Decisions taken in VE are generally based on the perception of distances and volumes. Therefore, the effectiveness of the decisions depends on the ability of customers to make judgments about what they see in the VE similar to the judgments they would have made in the corresponding real environment. Several studies have shown that the estimation of distances in VE is different from the estimation in real environment. Several factors can be the source of this problem such as the display device, the limited field of view, graphical quality, etc. Despite these studies, factors that cause this phenomenon remain unclear, and diverse. Our work is part of an architectural project: CIMBEES project. This project aims to integrate VR in the process of selling / buying and of the design through virtual visits and project review in VE. Our work is to design and evaluate architectural project review tool. The design stage is to suggest a project review tool for the visualization of digital mockups at real scale in VE and providing interaction that meets the needs of architects. During this stage we developed a project review tool and we modeled necessary digital mockups from real house plans. In the evaluation stage of the architectural project review tool, we were interested at the problem of the perception of distances in VE. The aim of this evaluation is to identify and to study the most important factors for the tool, to propose suitable parameters for our application context (virtual visits). To do this, we conducted an experimental study that focuses on the study of the influence of three factors on the perception of distances: 1) the cognitive profile of users, 2) the environmental context and 3) the speed of navigation. [...]

Les Interfaces Cerveau-Ordinateur basées sur l’Imagerie Mentale (IM-ICO) permettent auxutilisateurs d’interagir uniquement via leur activité cérébrale, grâce à la réalisation de tâchesd’imagerie mentale. Cette thèse se veut contribuer à l’amélioration des IM-ICO dans le but deles rendre plus utilisables. Les IM-ICO sont extrêmement prometteuses dans de nombreuxdomaines allant de la rééducation post-AVC aux jeux-vidéo. Malheureusement, leurdéveloppement est freiné par le fait que 15 à 30% des utilisateurs seraient incapables de lescontrôler. Nombre de travaux se sont focalisés sur l’amélioration des algorithmes de traitementdu signal. Par contre, l’impact de l’entraînement des utilisateurs sur leur performance estsouvent négligé. Contrôler une IM-ICO nécessite l’acquisition de compétences et donc unentraînement approprié. Or, malgré le fait qu’il ait été suggéré que les protocolesd’entraînement actuels sont théoriquement inappropriés, peu d’efforts sont mis en oeuvre pourles améliorer. Notre principal objectif est de comprendre et améliorer l’apprentissage des IMICO.Ainsi, nous cherchons d’abord à acquérir une meilleure compréhension des processussous-tendant cet apprentissage avant de proposer une amélioration des protocolesd’entraînement afin qu’ils prennent en compte les facteurs cognitifs et psychologiquespertinents et qu’ils respectent les principes issus de l’ingénierie pédagogique. Nous avonsainsi défini 3 axes de recherche visant à investiguer l’impact (1) de facteurs cognitifs, (2) de lapersonnalité et (3) du feedback sur la performance. Pour chacun de ces axes, nous décrivonsd’abord les études nous ayant permis de déterminer les facteurs impactant la performance ;nous présentons ensuite le design et la validation de nouvelles approches d’entraînementavant de proposer des perspectives de travaux futurs. Enfin, nous proposons une solution quipermettrait d’étudier l’apprentissage de manière mutli-factorielle et dynamique : un systèmetutoriel intelligent. / Mental-imagery based brain-computer interfaces (MI-BCIs) enable users to interact with theirenvironment using their brain-activity alone, by performing mental-imagery tasks. This thesisaims to contribute to the improvement of MI-BCIs in order to render them more usable. MIBCIsare bringing innovative prospects in many fields, ranging from stroke rehabilitation tovideo games. Unfortunately, most of the promising MI-BCI based applications are not yetavailable on the public market since an estimated 15 to 30% of users seem unable to controlthem. A lot of research has focused on the improvement of signal processing algorithms.However, the potential role of user training in MI-BCI performance seems to be mostlyneglected. Controlling an MI-BCI requires the acquisition of specific skills, and thus anappropriate training procedure. Yet, although current training protocols have been shown tobe theoretically inappropriate, very little research is done towards their improvement. Our mainobject is to understand and improve MI-BCI user-training. Thus, first we aim to acquire a betterunderstanding of the processes underlying MI-BCI user-training. Next, based on thisunderstanding, we aim at improving MI-BCI user-training so that it takes into account therelevant psychological and cognitive factors and complies with the principles of instructionaldesign. Therefore, we defined 3 research axes which consisted in investigating the impact of(1) cognitive factors, (2) personality and (3) feedback on MI-BCI performance. For each axis,we first describe the studies that enabled us to determine which factors impact MI-BCIperformance; second, we describe the design and validation of new training approaches; thethird part is dedicated to future work. Finally, we propose a solution that could enable theinvestigation of MI-BCI user-training using a multifactorial and dynamic approach: an IntelligentTutoring System.

Le vieillissement normal est caractérisé par un déclin cognitif subtil. Ce vieillissement cognitif est hétérogène : il existe des différences inter- et intra-individuelles dans la nature et l’étendue du déclin cognitif. L’hétérogénéité inter-individuelle se manifesterait par la présence de plusieurs profils cognitifs distincts parmi les personnes âgées normales (PAN). L’hétérogénéité cognitive peut également s’observer de manière intra-individuelle par une plus grande variabilité, soit une plus forte dispersion, dans les performances cognitives lors d’un contexte d’évaluation neuropsychologique chez un individu. Chez les PAN, certains profils cognitifs et mesures de dispersion ont été associés à un risque de développer une démence. Par ailleurs, la présence de biomarqueurs de la maladie d’Alzheimer (MA) est retrouvée chez une proportion significative de PAN et ces biomarqueurs auraient un impact délétère sur le fonctionnement cognitif dans le vieillissement normal. Ainsi, l’objectif de cette thèse est de mieux comprendre l’impact de différents biomarqueurs de la MA sur le fonctionnement cognitif des PAN, plus spécifiquement sur l’hétérogénéité cognitive que l’on retrouve au sein du vieillissement normal. Dans le cadre de cette thèse, composée de deux articles, 104 PAN ont réalisé une évaluation neuropsychologique approfondie, un examen de tomographie par émission de positons (PIB-TEP) permettant de quantifier la présence cérébrale du peptide bêta-amyloïde (βA), ainsi qu’un examen d’imagerie par résonance magnétique (IRM) permettant de mesurer les hyperintensités de la substance blanche (HSB) ainsi que l’épaisseur corticale. Le premier article de cette thèse porte sur l’hétérogénéité cognitive inter-individuelle. Les objectifs étaient : (1) de caractériser les différents profils cognitifs présents au sein du groupe PAN et (2) d’évaluer s’il existait des liens entre ces profils et les biomarqueurs de la MA. Trois profils cognitifs ont été identifiés : un profil où les performances cognitives sont globalement supérieures à la moyenne de l’échantillon, un profil où les performances sont généralement dans la moyenne et un dernier profil, minoritaire, où la majorité des performances se situent sous la moyenne. Uniquement ce dernier profil était associé à une charge amyloïde accrue et la présence plus importante d’HSB. Ces résultats suggèrent qu’au sein du vieillissement normal, un sous-groupe de participants présente un fonctionnement cognitif sous-optimal qui est en lien avec la présence de biomarqueurs de la MA. Le deuxième article porte sur l’hétérogénéité intra-individuelle et avait pour objectif de déterminer si la dispersion cognitive était associée à la présence des biomarqueurs de la MA. Les résultats montrent que, globalement, la dispersion n’est pas significativement associée à la présence de biomarqueurs de la MA. Seuls les scores de dispersion pour les domaines de la mémoire épisodique et en fonctionnement exécutif étaient associés aux HSB. Ces résultats suggèrent que la dispersion dans le vieillissement cognitif normal n’est pas directement associée à la pathologie Alzheimer. Cependant, certains éléments de cette dispersion pourraient être en lien avec une santé cérébrovasculaire sous-optimale. En conclusion, les résultats de cette thèse sont discutés à la lumière des connaissances actuelles. Les implications théoriques et cliniques de ces résultats sont abordées et différentes pistes de recherches futures sont évoquées. / Normal aging is characterized by subtle cognitive decline. This cognitive decline is heterogeneous: there are interindividual and intraindividual differences in the nature and extent of cognitive decline. Interindividual heterogeneity is thought to be manifested by the presence of several distinct cognitive profiles among normal older adults. Cognitive heterogeneity can also be observed in an intraindividual fashion through greater variability, or greater dispersion, in cognitive performance, in the context of an individual's neuropsychological assessment. In normal aging, certain cognitive profiles and measures of dispersion have been associated with a risk of developing dementia. Additionally, the presence of Alzheimer's disease (AD) biomarkers is found in a significant proportion of normal older adults and these biomarkers have a deleterious impact on cognitive functioning in normal aging. Thus, the objective of this thesis is to better understand the impact of different AD biomarkers on the cognitive functioning of normal older adults, more specifically, on the cognitive heterogeneity that is found in normal aging. As part of this thesis, composed of two articles, 104 normal older adults carried out an in-depth neuropsychological evaluation and cerebral imaging scan, a positron emission tomography (PIB-PET) examination and a magnetic resonance imaging (MRI) exam, to measure cerebral beta-amyloid peptides, white matter hyperintensities (WMH) and cortical thinning. The first article of this thesis deals with interindividual cognitive heterogeneity. The objectives were: (1) to characterize the different cognitive profiles present within the normal older adult group and (2) to assess whether there are links between these profiles and AD biomarkers. Three cognitive profiles have been identified: a profile where cognitive performance is overall higher than the sample average, a profile where performance is generally average and a final profile, where the majority of performance is below the average. This last profile was the only one associated with a greater amyloid load and an increased presence of WMH. These results suggest that within normal aging, a subgroup of participants exhibits suboptimal cognitive functioning and that this cognitive functioning is related to a greater AD biomarkers presence. The second article examines intraindividual heterogeneity and aimed to determine whether or not cognitive dispersion is associated with the presence of AD biomarkers. The results show that overall, dispersion is not significantly associated with the presence of AD biomarkers. Only dispersion scores for the domains of episodic memory and executive functioning were associated with WMH. These results suggest that dispersion in normal cognitive aging is not directly associated with AD biomarkers. However, some elements of cognitive dispersion could be linked to suboptimal cerebrovascular health. In conclusion, the results of this thesis are discussed in light of current knowledge. The theoretical and clinical implications of these results are explored and various avenues for future research are proposed.