[pt] Esta dissertação tem como objetivo principal avaliar o desempenho linguístico de crianças com problemas de aprendizagem, de modo a verificar em que medida essas dificuldades equivalem às características do quadro do DEL (Déficit Específico da Linguagem). Pretende-se ainda avaliar o desempenho de crianças com problemas de aprendizagem por meio de uma tarefa clássica de crenças falsas para caracterização do desenvolvimento da Teoria da Mente (ToM), tendo em vista que esse desenvolvimento tem sido apontado como comprometido diante de um déficit linguístico. Este trabalho também visou a ampliar a amostra de crianças sem queixas de linguagem submetidas à  avaliação por meio do MABILIN (Módulos de Avaliação de Habilidades Linguísticas), em desenvolvimento no LAPAL (Laboratório de Psicolinguí­stica e Aquisição da Linguagem - PUC-RIO), na padronização do teste, de modo a obter-se uma caracterização do desenvolvimento linguístico no Português do Brasil (PB), que possa ser tomada como referência na avaliação de problemas de linguagem e, particularmente, do DEL. Foram avaliadas 30 crianças de cerca de 6 anos de idade, com e sem queixas de aprendizagem, de nível sócio-econômico baixo na rede de ensino público da Secretaria de Estado de Educação do Distrito Federal. Os resultados obtidos mostram que o desempenho de crianças com queixas de aprendizagem foi, de maneira geral, inferior ao das crianças sem queixas de aprendizagem. Tanto em tarefas de compreensão de sentenças simples ativas, passivas reversíveis/irreversíveis, coordenadas, relativas e interrogativas QU, como em tarefas cuja compreensão se faz dependente de concordância de gênero e número, a diferença entre as crianças com queixas de aprendizagem e as crianças sem queixas mostrou-se significativa. Os resultados indicam dificuldades de ordem linguística compartilhadas com o DEL, ainda que o efeito de grupo, independentemente das variáveis linguísticas manipuladas, apontando para um pior desempenho do grupo com queixas de aprendizagem, sugira dificuldades de outra ordem interferindo no desempenho linguístico. O resultado no teste de ToM revela que o grupo de crianças com queixas de aprendizagem, mais do que grupo controle, tem dificuldade em prever a ação de um personagem a partir da atribuição de uma crença falsa a este. Dificuldades no uso de pistas para a solução de tarefas linguísticas e na elaboração de inferências dependentes de ToM pode, portanto, comprometer o desempenho escolar desse grupo. / [en] The primary aim of this dissertation is to evaluate the linguistic performance of 30 children with learning impairment in order to verify the extent to which these difficulties are equivalent to those that characterize the performance of SLI (Specific Language Impairment) children. The performance of children with learning impairment was also evaluated by means of a classic false belief task intended to assess their development as far as Theory of Mind is concerned, since this development has been pointed to be compromised in face of linguistic impairment. Moreover, this research aimed to enlarge the sample of children without language impairment whose linguistic performance is assessed by means of a set of tests (Modules for the Evaluation on Linguistic Abilities), that has been developed in LAPAL (Laboratório de Psicolinguí­stica e Aquisição de Linguagem - PUC-RIO), intended to identify those aspects of language that are particularly affected in SLI Brazilian Portuguese speaking children. The performance of 30 children with and without learning impairment, of low economical background and age average by 6 years old was evaluated at a public school in the outskirts of Brasilia, Federal District, Brazil. The results show that the performance of children with learning impairment was, generally, lower in comparison with children without learning impairment. The performance in comprehension tasks focusing on simple active and passive sentences, reversible/irreversible, coordinated, relative clauses, WH interrogatives, and in tasks focusing on the processing of gender and number agreement was significantly different between children with and without learning impairment. The results indicate linguistics difficulties shared with Specific Language Impairment in the learning impaired group, even though the effect of group, independently of the linguistic variable manipulated, suggests that difficulties of a different order might affect their linguistic performance. The result of the test of false belief task shows that the group with learning impairment, more than the control group, has difficulty in foreseeing the action of a character from a false belief attribution. Difficulties in using clues in the solution of the linguistic tasks and in the elaboration of dependent inferences of ToM can therefore impair the school performance of this group.

The association between extent of chronic cannabis use (CCU-extent) and cognitive impairment among adolescents has been the subject of controversial debate. Linking DNA methylation to CCU-extent could help to understand cannabis associated changes in cognitive performance. We analyzed cognitive task performances, CpG methylation in peripheral whole-blood samples and self-reported past-year CCU-extent of n = 18 adolescents (n = 9 psychiatric outpatients with chronic cannabis use (CCU), n = 9 without) who were matched for age, gender and psychiatric disorders. Patients with CCU were at least 24 h abstinent when cognitive tasks were performed. A Principal Component Analysis (PCA) was carried out to identify group differences in whole genome DNA methylation. Mediation analyses were performed between CCU-extent associated CpG sites and CCU-extent associated variables of cognitive tasks. PCA results indicated large differences in whole genome DNA methylation levels between the groups that did not reach statistical significance. Six CpG sites revealed reduced methylation associated with CCU-extent. Furthermore, CCU-extent was associated with lower scores in verbal learning. All six CpG sites mediated the effects between CCU-extent and verbal learning free recall. Our results indicate that CCU is associated with certain patterns in the methylome. Furthermore, CCU-extent associated impairments in memory function are mediated via differential methylation of the six CCU-associated CpG sits. Six identified CpG are located in genes previously described in the context of neurodegeneration, hippocampus-dependent learning and neurogenesis. However, these results have to be carefully interpreted due to a small sample size. Replication studies are warranted.