Ce travail est divisé en deux parties : la première partie concerne l'évaluation de la sélection attentionnelle dans une tâche de Mémoire visuelle à Court-Terme. Nous avons testé, dans cette partie, la capacité des participants à sélectionner et mémoriser des cibles parmi des distracteurs. Nos résultats ont mis en évidence la capacité à mémoriser quatre objets sélectionnés parmi un ensemble de distracteurs sans l'intervention de mécanismes physiologiques tels que les saccades oculaires. En outre, nous avons montré que cette capacité est sensible à l'organisation spatiale des cibles parmi les distracteurs. A travers plusieurs expériences manipulant l'organisation spatiale des objets, le niveau d'exigence de la tâche, la différence entre l'objet test et celui présenté préalablement à la même localisation, nous avons mis en évidence l'impact de l'organisation spatiale des objets d'une part sur l'allocation attentionnelle sur les localisations et d'autre part sur le traitement des cibles apparaissant dans ces localisations. La proximité spatiale des objets serait un facteur facilitateur lors de l'allocation attentionnelle mais elle rendrait le traitement plus difficile. Dans la deuxième partie, nous avons combiné la méthode de prévisualisation des distracteurs avec le paradigme de report partiel pour examiner l'effet du nombre des localisations servant d'indices sur la capacité d'allocation attentionnelle et l'effet du nombre des cibles indicées sur la capacité de traitement. / The aim of this thesis is twofold : the first dealt with the assessment of the attentional selection in a Visual Short Term-Memory task. We tested the capacity of the participants in selecting and memorizing targets among distractors. Our results provided evidence for the capacity to memorize four selected objects among a set of distractors without the involvement of physiological mechanisms like eye-movements. Furthermore, we showed that this capacity is sensitive to the spatial organization of targets among distractors. In further experiments, we manipulated the spatial organization of objects, the requirement of the task, the difference between the test object and the object previously presented at the same location. The results highlighted the impact of the spatial organization of objects on the attentional allocation over locations and the processing of targets appearing at these locations. The spatial proximity of objects greatly facilitated the attentional allocation but made the processing more difficult. The second aim dealt with the combination of the preview of distractors method with the partial report paradigm to examining i) the effect of the number of locations serving as cues on the attentional allocation capacity and ii) the effect of the number of objects on the processing capacity. We showed that the division of attention over several objects is limited by the difficulties associated with attentional allocation beyond two selected locations and the difficulties associated with processing beyond two encoded objects.

This study proposes an accuracy comparison of two of the best performing machine learning algorithms in natural language processing, the Bayesian Network and the Long Short-Term Memory (LSTM) Recurrent Neural Network, in detecting Alzheimer’s disease symptoms in conversation transcripts. Because of the current global rise of life expectancy, the number of seniors affected by Alzheimer’s disease worldwide is increasing each year. Early detection is important to ensure that affected seniors take measures to relieve symptoms when possible or prepare plans before further cognitive decline occurs. Literature shows that natural language processing can be a valid tool for early diagnosis of the disease. This study found that mild dementia and possible Alzheimer’s can be detected in conversation transcripts with promising results, and that the LSTM is particularly accurate in said detection, reaching an accuracy of 86.5% on the chosen dataset. The Bayesian Network classified with an accuracy of 72.1%. The study confirms the effectiveness of a natural language processing approach to detecting Alzheimer’s disease.

L’ambition de la thèse est de contribuer à une meilleure compréhension des difficultés cognitives rencontrées par les enfants sourds munis d’un implant cochléaire (IC). Elle présente une recension de travaux et une étude originale concernant la mémoire à court-terme/mémoire de travail.Est évalué l’apport recommandé de la lecture labiale et des clés de la LPC (Langue Parlée Complétée) sur le rappel.Une série d’épreuves originales de rappel immédiat a été conçue sur support informatique. Elle comprend des tâches contrastées du point de vue de la nature de l’information à mémoriser (spatiale vs verbale) et des modalités de présentation de l’information. Les épreuves ont été validées auprès d’une population d’enfants normo-entendants (NE)(âgés de 6 à 8 ans, N=42). Les réponses d’enfants IC(N=14) ont été comparées à celles d’enfants NE, sur la base de la constitution de deux groupes appareillés selon les critères d’âge, de sexe et d’aptitude intellectuelle.Pour les deux groupes, le rappel immédiat est meilleur pour les informations visuo-spatiales. Les informations verbales sont moins bien retenues par les enfants IC. Contrairement aux attentes, l’apport de la LPC, spécifiquement dans la modalité verbale, ne conduit pas à une augmentation des performances des enfants sourds. L’analyse de l’ordre de rappel des items ne fait pas apparaître de difficultés spécifiques. En revanche, la longueur des listes est préjudiciable en verbal. L’analyse des erreurs atteste de leurs difficultés au plan des connaissances langagières. Une analyse fine des performances individuelles montre des profils différenciés attestant de la singularité des modes d’adaptation des enfants sourds IC. / The aim of the thesis is to contribute to a better understanding of cognitive difficulties in deaf children with a cochlear implant (CI). Firstly, this thesis presents a comparative analysis of previous research work. Secondly, it presents an original study addressing short-term memory (STM)/working memory (WM) issues, in which the contribution of cued speech (CS) is assessed on memorization performances. To do so, a novel STM/WM task series was developed and used to investigate whether the use of verbal stimuli versus spatial stimuli differentially affects immediate memory processes and to examine whether the presentation of items in an enriched context has a benefit on the immediate memory capacity. The developed tasks were validated on normal-hearing (NH) children (6- and 8-year-old, N=42) and the capacities of CI deaf children(N=14) were compared to those of their NH peers matched for age, sex and reasoning ability. For both groups, the immediate recall proves to be better for visuo-spatial information. Also, CI deaf children appear as memorizing less verbal information. Surprisingly, CS, appears to be ineffective to improve the CI deaf children performances, especially in the verbal modality case; if the analysis of the order of recall of items does not reveal any specific difficulty, the length of the items lists is harmful in the verbal modality. The analysis of the recall errors confirms difficulties in linguistic knowledge. Individual performances of CI deaf children show diverse patterns.

Objetivo: Estudar a estruturação hierárquica da sintaxe em crianças com distúrbios de linguagem. Foram pesquisados os quadros de Distúrbio Específico de Linguagem (DEL), Distúrbios do Espectro Autístico (DEA) e Síndrome de Down (SD). O objetivo principal desta pesquisa foi avaliar e comparar a designação sintática estrutural, por meio da compreensão de sentenças com predicativos e pronomes reflexivos ligados a um substantivo não adjacente, de modo a testar a hipótese do Déficit de Ordenação Hierárquica (DOH). Essa hipótese postula que crianças com distúrbios de linguagem têm dificuldade em estabelecer relações não adjacentes (hierárquicas) entre os elementos de uma frase. Esta pesquisa também avaliou se uma demanda adicional de memória de trabalho, em construções contendo pronomes reflexivos, afeta a designação sintática estrutural em crianças com DEL, DEA e SD. Método: Sessenta e duas crianças falantes do Português Brasileiro (40 meninos e 22 meninas) entre 7; 0 e 14; 2 anos de idade participaram de dois estudos que investigaram a designação sintática de predicativo e de pronome reflexivo. O Estudo I comparou o desempenho de crianças com DEL e crianças com desenvolvimento típico de linguagem (DTL). O Estudo II comparou o desempenho de crianças com DEL, DEA, SD e seus pares com DTL. O experimento consistiu em uma tarefa computadorizada de compreensão de sentenças desenvolvida no software E-Prime. Cada criança respondeu a 72 ensaios apresentados aleatoriamente, de modo a evitar efeitos de ordem ou familiarização. Em cada ensaio, a criança foi apresentada a uma frase contextual (duração máxima de 5500 ms) e, após um intervalo entre estímulos de 1000 ms, a frase alvo (duração máxima de 5000 ms) e o estímulo visual (quatro figuras) foram apresentados simultaneamente. Resultados: No Estudo I, as crianças com DEL foram significativamente menos precisas em todas as condições. Diferentes distribuições de erro foram observadas nas duas condições de memória de trabalho. Ambos os grupos apresentaram mais erros acarretando em construções sintáticas incorretas na condição de longa demanda de memória de trabalho. No Estudo II, crianças com DEL, DEA e SD apresentaram pior desempenho quando comparadas às crianças com DTL. Os grupos DEA e SD apresentaram padrões de resposta semelhantes entre si em diferentes condições. As crianças com DEL apresentaram desempenho similar ao de crianças com DEA e SD apenas quando as demandas de memória de trabalho foram maiores. Conclusões: A hipótese DOH não foi confirmada. Crianças com DEL, DEA e SD se diferenciam de crianças com DTL na compreensão de sentenças com predicativos e reflexivos onde o conhecimento da designação sintática estrutural é necessário. Existem semelhanças entre as crianças com DEA e SD na compreensão destas estruturas. Diferentes efeitos de memória de trabalho na compreensão sintática são encontrados de acordo com o distúrbio de linguagem / Purpose: To study the hierarchical syntactic structuring in children with language disorders. The research involved children with Specific Language Impairment (SLI), Autism Spectrum Disorders (ASD), and Down Syndrome (DS). The main purpose of this dissertation was to examine and compare the syntactic structural assignment, through the comprehension of sentences with predicates and reflexives that are linked to a non-adjacent noun, as a test of the Hierarchical Ordering Deficit Hypothesis (HOD). That hypothesis posits that children with language impairment have difficulty in establishing non-adjacent (hierarchical) relations among elements of a sentence. This dissertation also tested whether additional working memory demands in constructions containing reflexives affected the syntactic assignment of children with SLI, ASD and DS. Method: Sixty-twoBrazilian Portuguese-speakingchildren (40 boys and 22 girls) between 7;0 and 14;2 years of age participated in two studies that investigated the syntactic assignment of predicates and reflexives. Study I compared performance of children SLI to children with typical language development (TLD). Study II compared the performance of children with SLI, ASD, DS and TLD peers. The experiment consisted on a computerized sentence comprehension task designed on E-Prime software. Each child responded to 72 trials which were randomly presented to avoid order or familiarization effects. For each trial, the child was presented with a context sentence (maximum duration of 5500 ms) and, after an interstimulus interval of 1000 ms, the target sentence (maximum duration of 5000 ms) and the visual stimuli (four pictures) were presented simultaneously.Results:In Study I, children with SLI were significantly less accurate on all conditions. Different error distributions were observed on the two working memory conditions. Both groups made more errors resulting in incorrect syntactic construction in the long working memory condition. In Study II, children with SLI, ASD, and DS exhibited poorer overall performance than TLD children. The groups of ASD and DS exhibited similar response patterns across conditions. Children with SLI exhibited similar performance to the DS and ASD children only when working memory demands were higher. Conclusion: The HOD hypothesis was not confirmed. Children with SLI, ASD and DS differ from children with TLD on the comprehension of predicate and reflexive structures where knowledge of syntactic structural assignment is required. There are similarities between children with ASD and DSon the comprehension of these structures. Working memory has different effects in syntactic comprehension depending on the language disorder.

Lithium continues to be widely prescribed for the management of bipolar disease, yet cognitive impairment-related side effects promote noncompliance of the treatment regimen. We have introduced a novel animal model, the black molly fish, to study dose-response effects of lithium on short-term (STM) and long-term (LTM) memories. We developed a method utilizing capillary ion analysis (CIA), to measure plasma and brain lithium levels employed in our behavioral studies. We then developed an appropriate testing environment to ascertain learning capacities of these fish. We established that black mollies could adequately perform a forced-choice spontaneous alternation (SA) task used extensively in rodents as an index of spatial STM. Employing this paradigm we designed a dose-response experiment utilizing chronic lithium regimens with a wide range of dosage groups to assess STM in the black molly. Results of the experiment indicated a robust effect in which performances of all dose groups were impaired in different degrees but not dose dependently. Using the same dosing regimen, we tested subjects in a place-learning task to assess dose-response effects of lithium on spatial LTM. A variety of performance measures were analyzed presenting a consistent theme implicating significant impairment with the high dose group. CIA results for the STM and LTM experiments revealed consistent linear relationships between mean plasma and brain lithium levels and lithium dosages. We have immunolocalized a 5-HT1A-like receptor from the caudal midbrain of black mollies, an area structurally homologous to the mammalian raphe nuclei. This autoinhibitory receptor is considered to be involved in the regulation of firing of raphe serotonergic fibers and 5-HT release in terminal projection areas such as the hippocampus and frontal cortex. Downregulation of these receptors initiates excessive serotonin availability that may relieve symptoms of depression yet paradoxically impair cognition. It is unclear whether activity in the presynaptic raphe nuclei or the postsynaptic projection areas is responsible for these phenomena. Because the black molly is not equipped with postsynaptic 5-HT1A receptors it offers a unique opportunity to study the effects of lithium on the presynaptic form of the receptor without compensating effects of the postsynaptic form exhibited in the mammal.

This study examined the short term memory (STM) difference of magnetic resonance imaging (MRI) technologists versus non-MRI technologists. Human and animal studies have indicated that residual magnetic fields have caused changes within the cerebral structure. Research on residual magnetic fields and their effect on STM is still at its infancy. A quasi-experimental design was used to determine if any significant difference existed between the STM of MRI technologists (n = x) and a control population sample (n = x). The STM of both groups was assessed with the use of the Rivermead Behavioural Memory Test-Third Edition. Solicitation of the participants was from a national MRI organization, the American Society of Radiologic Technologists, and community workers within the profession. The control group of participants was solicited through community board postings. Only the New York/New Jersey metro area and the New Hampshire/Maine area participants were used for this study. These participants were of various age ranges, genders, and educational levels. ANOVA and regression analyses were used to analyze the data. The study showed mixed results, indicating no significant STM difference in the overall memory scores of both groups F (1, 80) =3.061, p =..084, but it did show a significant difference in STM when it came to prospective memory, memory of planned events. These findings illustrate a need for further research in this area. Expanding the geographical reach and sample size could clarify the role of MRI on STM. The results of this study suggest that procedures that limit the exposure of the MRI technologists to the residual magnetic fields surrounding MRI machines could yield a reduction in loss of prospective memory.

The aim of this study is to investigate whether blind individuals display cognitive advantages over sighted individuals with regard to second language acquisition. Previous studies from neuropsychology have indicated that this is the case. It has been found that blind L1 speakers can compensate for loss of vision by developing better perceptual and cognitive skills compared to sighted individuals, skills that are highly relevant to language acquisition. These studies do not, however, investigate blind L2 speakers, for whom it is not clear whether these advantages are also found.  In all, 80 adults participated in the study: 40 L2 speakers of Swedish (11 early blind, 9 late blind, 20 sighted, AO<18) and a matching group and subgroups of L1 speakers. These speakers underwent tests on speech perception in noise, accentedness in an L2 and memory functions. The results revealed that L2 speakers are at a great disadvantage perceiving speech in noise compared to L1 speakers, and that there was no advantage associated with blindness. In the L1 speakers group, however, the results revealed that the early blind had advantages compared to the late blind and sighted in white noise, but that both blind groups were more negatively affected by babble noise than the sighted. The results in relation to accentedness in an L2 revealed that there were no advantages associated with blindness. The results further revealed there were no advantages associated with blindness on the episodic memory test. The results did, however, reveal that the early blind performed significantly better than the late blind and sighted on all phonological short-term memory tests and that both the early and late blind were significantly better than the sighted on recognition memory for new words, irrespective of language background. The conclusion is that blindness is associated with advantages in, for example, ability to learn new words and syntax, acquisition rate, ultimate L2 attainment, and language aptitude.

Attention Deficit Hyperactivity Disorder (ADHD) is one of the most prevalent conditions among school children. Executive function deficits representing difficulties in maintaining an appropriate problem set for the attainment of future goals are reported to be the major deficit in ADHD populations. There is a high rate of co-morbidity of learning disabilities and ADHD, with empirical evidence indicating an association with math and reading difficulties, but there is little research on the written expression of this population. There is a body of emergent research indicating that written expression is mediated by executive function. Written expression is a complex task that is affected by motivation, working memory, cognitive processes and long term memory, factors which are reported to be compromised in ADHD populations. This study evaluated the working memory and fluid reasoning in children with (combined and predominantly inattentive types) and without ADHD. Second, it explored the relationship between working memory and fluid reasoning on written expression in children with and without ADHD. Finally, the possible link between the executive functions of working memory and fluid reasoning, with written expression of children with and without ADHD was examined. The findings of this study indicate that children with the combined type of ADHD had lower written expression and working memory scores compared to children with the inattentive type of ADHD. The results of this study also indicated an association between disinhibition and working memory deficits on written expression performance. This research will serve to contribute to an understanding of the functional impact of ADHD on academic performance. Findings from this study could potentially help with interventions for deficits in written expression among school children.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal