Les mécanismes de plasticité associés aux accidents vasculaires cérébraux ischémiques (AVCi) ont été largement étudiés dans le cortex moteur des souris. Bien que les déficits moteurs soient communs et apparents, un AVCi peut également altérer les fonctions sensorielles comme la vision et provoquer une cécité corticale qui se manifeste par une perte complète de la vision. En comparaison, les mécanismes neurologiques sous-jacents des déficits visuels engendrés par les AVCi sont peu décrits. Ces troubles visuels peuvent survenir lorsque des aires corticales visuelles ou non-visuelles sont lésées, néanmoins, l’implication des aires visuelles primaires est plus fréquemment relevée. Une récupération partielle des fonctions visuelles est possible, mais elle est rarement complète. Maintenant que la souris est considérée comme un excellent modèle animal pour les neurosciences de la vision, il est désormais très pertinent d’explorer les mécanismes de plasticité des AVCi dans le cortex visuel en utilisant des approches similaires à celles employées dans le cortex moteur. L’imagerie calcique mésoscopique est particulièrement appropriée pour étudier longitudinalement la plasticité des circuits neuronaux à l’échelle du cortex. Le but a été de développer un modèle préclinique de cécité corticale en mesurant l’activité cérébrale spontanée et évoquée après une lésion photothrombotique dans le cortex visuel primaire de souris à l’aide de l’imagerie calcique mésoscopique. Une diminution de l’activité neuronale spontanée, combinée à une augmentation de l’excitotoxicité et une réduction locale de la perfusion sanguine, ainsi qu’une perte des fonctions visuelles ont été observées après l’induction de l’AVCi. Deux semaines plus tard, l’activité neuronale spontanée commençait à s’améliorer et une récupération partielle des réponses évoquées par les stimulations visuelles a été notée après un mois. La plupart des déficits fonctionnels observés en imagerie calcique corrélaient avec le volume de la lésion. Le développement de ce nouveau modèle expérimental ouvrira le chemin vers d’autres études s’intéressant aux mécanismes de la réorganisation fonctionnelle associés aux lésions dans le cortex visuel. / Stroke-related mechanisms, such as remapping and rewiring, have been widely studied in the motor cortex of mice. Although motor impairments are common after an ischemic stroke, it can also affect sensory function such as vision and manifest as a complete loss of vision known as cortical blindness. The underlying neurological mechanisms of visual deficits related to strokes are poorly described, but they can occur when non-visual and visual areas are damaged, still, the primary visual areas are most likely to be involved. Partial recovery of vision loss can happen, but it rarely leads to complete recovery. Now that the mouse is considered an excellent model for visual neurosciences, it would be relevant to explore stroke-related mechanisms in the visual cortex using similar approaches to motor studies. Among them, widefield calcium imaging (WCI) is particularly appropriate to study cortex-wide plasticity of neuronal circuits longitudinally. The goal of this study was to develop a preclinical model of cortical blindness by measuring spontaneous and visually evoked brain activity after a photothrombotic stroke in the primary visual area of mice using WCI. After the stroke, spontaneous neuronal activity fluctuations decreased and were associated with increased excitotoxicity and reduced blood perfusion. Spontaneous neuronal activity started to improve two weeks after the stroke. It was accompanied by a loss in visual responses that recovered partially 1 month after the stroke. Most functional deficits were correlated with lesion size. By providing this new experimental model, this study will hopefully pave the way for numerous subsequent studies interested in understanding the mechanisms of functional reorganization associated with brain lesions in the visual cortex.

Made available in DSpace on 2016-06-02T19:44:14Z (GMT). No. of bitstreams: 1 5134.pdf: 3904591 bytes, checksum: 196f7357f34d96d134a0ae6d9483aa8f (MD5) Previous issue date: 2013-03-05 / The literature has pointed to an increase in the incidence of children with visual impairments associated with neurological disorders and other disabilities, but the educational implications of the association of such impediments is considered a minor theme in the training of special education teachers. The present study aimed to develop and evaluate a collaborative consultation program in the field of visual impairment with a team of professionals of a special school for students with intellectual disabilities. The participants were the research/consultant, five teachers, two class assistants, a speech therapist, a physical therapist, a psychologist and an occupational therapist, plus 46 students with ages between 7 and 37 years. The study was carried out in three stages: preliminary step of conducting ethical procedures; Study-1, the diagnosis of institutional conditions; and Study-2, the intervention. The latter involved: a) theoretical training of 35 hours of lessons; b) practice based on case studies based on the development of a visual evaluation process of students, with the purpose of raising subsidies for educational planning and to apply the theoretical knowledge in practice; and c) final evaluation of the consultation/training program. The results of student s characterization showed that 30.4% were diagnosed with cerebral palsy; 30.4% with intellectual disabilities; 19.6% with Down syndrome, and 19.6% with other diagnoses. 83% of the students have already been through ophthalmological inspection with an average age of 4.2 years in first query. Two students were diagnosed with optic nerve atrophy and congenital cataracts, which was not reported by the parents to the school. As for the observation of visual difficulties, the parents have made 11 references, whereas the professionals made only 3. The results of the evaluation process of visual changes, duly complemented by medical information, were: 16 students (34.8%) showed no detected changes; 20 (43.5%) with minor changes (strabismus, refraction errors); 3 (6.5%) with visual impairment of ocular origin; 3 (6.5%) with cortical visual impairment; 1 (2.1%) with ocular and cortical visual impairment; and 3 (6.5%) with suspicion of visual impairment. The visual impairment was predominant among the cases of cerebral palsy. The case studies resulted in referrals to ophthalmological consultations, guidance to parents, propositions of pedagogical strategies, in addition the adjustment of materials and environment. The results concerning the evaluation of the collaborative consultation program showed that it was satisfactory regarding the professional development of the consultant and the consultees and regarding the possibilities of solving the addressed problem. The study highlights the need of ophthalmic and visual development assessment among students with intellectual and multiple disabilities and emphasizes the importance of collaborative practice between specialists, family and school professionals to an understanding of the problem of a student with visual impairment associated with intellectual or multiple disabilities. In addition, it suggests the need of a support network for teachers of special education, of generalist formation, what also includes teachers specialized in the visual impairment area, as well as other professionals with technical knowledge. / A literatura tem apontado um aumento na incidência de crianças com deficiência visual associada a distúrbios neurológicos e a outras deficiências, sendo as implicações educacionais da associação desses impedimentos um tema pouco considerado na formação dos professores de educação especial. O presente estudo teve como objetivo desenvolver e avaliar um programa de consultoria colaborativa na área da deficiência visual junto a uma equipe de profissionais de uma escola especial para alunos com deficiência intelectual. Foram participantes o pesquisador/consultor, cinco professoras, duas auxiliares de classe, uma fonoaudióloga, uma fisioterapeuta, uma psicóloga e uma terapeuta ocupacional, além de 46 alunos, de 7 a 37 anos. O estudo foi desenvolvido em três etapas, a saber: Etapa Preliminar de condução dos procedimentos éticos; Estudo 1, do diagnóstico das condições institucionais; e Estudo 2 da intervenção. Esta última envolveu: a) formação teórica de 35 horas/aula; b) parte prática baseada em estudos de casos através do desenvolvimento de um processo de avaliação visual dos alunos com a finalidade de levantar subsídios para o planejamento pedagógico e de aplicar na prática os conhecimentos teóricos; e c) avaliação final do programa através de análise de conhecimentos pré e pós-programa, entrevista e avaliação quantitativa pelos profissionais. Os resultados de caracterização dos alunos mostraram 30,4% com diagnóstico de paralisia cerebral; 30,4% com deficiência intelectual; 19,6% com síndrome de Down, e, 19,6% com outros diagnósticos. Haviam realizado consulta oftalmológica, 83,0% dos alunos, com uma média de idade da primeira consulta de 4,2 anos. Dois alunos tiveram diagnóstico de atrofia de nervo óptico e um de catarata congênita, que não foi comunicada pelos pais à escola. Quanto à observação de dificuldades visuais os pais fizeram 11 referências, enquanto os profissionais apenas três. Os resultados da avaliação das alterações visuais dos alunos complementada por informações médicas identificaram: 16 alunos (34,8%) sem alterações detectadas; 20 (43,5%) com alterações leves (estrabismo, erros de refração); três (6,5%) de deficiência visual de origem ocular; três (6,5%) de deficiência visual cortical; um (2,1%) com deficiência visual ocular e cortical; e três (6,5%) com suspeita de deficiência visual. A deficiência visual foi predominante entre os casos de paralisia cerebral. Os estudos de casos resultaram em encaminhamentos para consultas oftalmológicas, orientação aos pais, proposição de estratégias pedagógicas além de adaptação de materiais e ambiente. Os resultados quanto à avaliação do programa de consultoria colaborativa mostraram que foram satisfatórios do ponto de vista do desenvolvimento profissional, de ambas as partes, consultor e consultantes, e quanto às possibilidades de resolução da problemática abordada. O estudo destaca a necessidade da avaliação oftalmológica e do desenvolvimento visual entre alunos com deficiência intelectual e múltipla, e enfatiza a relevância da prática colaborativa entre especialistas, profissionais da escola e família para a compreensão da problemática do aluno com deficiência visual associada à deficiência intelectual ou múltipla. Além disso, sugere a necessidade de uma rede de apoio para os professores de educação especial, de formação, generalista, que inclui também professores especializados na área da deficiência visual, assim como outros profissionais com conhecimentos técnicos.