Le modèle computo-fonctionnel de la vision de haut niveau de Kosslyn et Koenig (1992) repose sur la dissociation entre la reconnaissance et le traitement spatial de la scène visuelle. En 1987, Kosslyn postula l’existence de deux processus pour le traitement des relations spatiales : un processus catégoriel qui calcule les positions relatives des objets et un processus coordonné qui calcule la distance entre les objets. Des études utilisant le paradigme de présentation en champ visuel divisé ont mis en évidence que l’hémisphère gauche sous-tendrait un traitement catégoriel ; l’hémisphère droit sous-tendrait un traitement coordonné. Cette interaction semblerait valider la dichotomie des deux types de processus.Une revue de la littérature pluridisciplinaire a été menée afin de savoir si ce fait est suffisant pour rejeter l’hypothèse d’un processus unique pour les traitements catégoriels et coordonnés. Entre autres, plusieurs études ont observé un effet de pratique au cours de la réalisation de jugements coordonnés : une diminution de l’intervention de l’hémisphère droit au profit d’une prise en charge progressive de l’hémisphère gauche. De plus, l’avantage de l’hémisphère gauche pour le traitement catégoriel a été rarement observé.Une série de cinq expériences comportementales ont été conduites pour vérifier certains biais expérimentaux qui pourraient expliquer les différences hémisphériques et l’effet de pratique observés. Nos résultats nous ont permis d’avancer des hypothèses axées sur la communication entre les hémisphères et sur un lien entre les processus catégoriels et coordonnés. Une critique du paradigme de présentation en champ visuel divisé et différents modèles d’interaction hémisphérique ont été présentés. Trois expériences ont été menées, afin d’évaluer l’impact des communications hémisphériques dans le traitement des relations spatiales. A la lumière de nos résultats, la dichotomie des processus catégoriels et coordonnés a été discutée. / The computational-functional conception of high-level processing of vision in Kosslyn and Koenig (1992) relies on dissociation between object recognition and spatial processing. In 1987, Kosslyn postulated that two different processes compute spatial-relations: categorical process computes relative position of objects and coordinate process computes the distance between objects. Some studies indicate a left-hemisphere advantage for processing categorical spatial relations and a right-hemisphere advantage for processing coordinate spatial relations. This hemispheric difference is interpreted as an evidence of a dichotomy between these two processes. A pluridisciplinary review was conducted to assure that single process hypothesis is dismissed out. Some studies showed, in a coordinate task, that practice resulted in a decreased right-hemisphere involvement and a concurrent increase in left-hemisphere involvement (i.e., practice effect). Furthermore, the left-hemisphere advantage in categorical was seldom observed. The theoretical aim of the thesis was based on two questions: (1) Are there single or several processes encoding visual spatial relations? (2) How can we interpret this practice effect ?Five experiments were run to verify possible bias which might explain observed hemispheric differences and practice effect. Our results suggested that hemispheric communication might be an important factor in spatial-relation processing.An theoretical investigation of divided visual field paradigm was led and several interhemispheric models were described. Three experiments were conducted to estimate hemispheric communication in spatial-relation process. In the light of our results, separate categorical-coordinate processes hypothesis were discussed.

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Objetivo: Investigar a influência do posicionamento da fóvea em relação à cabeça do nervo óptico (CNO) sobre resultados da perimetria padrão automatizada (PPA) central em pacientes com glaucoma e com defeitos patológicos localizados na rima temporal inferior (DTI) da CNO. Casuística e Métodos: Cinquenta e sete olhos de 35 pacientes com GPAA foram incluídos e divididos em dois grupos: um grupo com DTI (18 olhos) e outro com sem DTI (39 olhos). Três parâmetros diferentes obtidos a partir de uma tomografia de coerência óptica de domínio espectral (OCT-SD), ângulo do disco à fóvea (ADF), desvio vertical da fóvea (DVF) da linha média e diferença angular de defeito (DAD) entre borda DTI e ADF, foram correlacionados com quatro setores no programa 10-2: hemicampo superior, borda superior, borda nasal e arco súperonasal. As correlações foram testadas por meio de análises de regressão com modelos de efeitos mistos e interceptações aleatórias. Resultados: Os valores médios (± DP [Desvio padrão]) de ADF, DAD e DVF foram, respectivamente: -5,0 ± 4,4º, 43,3º ± 17,3º e -1346,6 µm ± 1609,0 µm. Comparações múltiplas mostraram que nos olhos com DTI, tanto DVF como DAD, mas não ADF, afetam significativamente os setores do campo visual (CV). As regressões binomiais de ROC demonstraram que apenas os valores de corte do 95º percentil de DVF (- 3264,5 µm) e DAD (70,5º) podem promover mudanças de sensibilidade na borda superior dos setores do programa 10-2 [DVF: AUC = 0,60 (95%CI = 0,50 - 0,71); DAD: AUC = 0,83 (IC 95% = 0,70 - 0,912)]. Conclusões: A localização vertical da fóvea e o seu posicionamento relativo aos limites do DTI interferiram nas alterações de sensibilidade de pontos periféricos do hemicampo superior, no programa 10-2. Como o ADF, isoladamente, não influenciou significativamente nessas alterações, outros ajustes utilizando posicionamento foveal e parâmetro da OCT devem ser considerados na avaliação da PPA central em pacientes com defeitos glaucomatosos localizados na CNO. / Purpose: To investigate the effects of the fóvea positioning relative to the optic disc on the 10-2 visual field (VF) in glaucoma patients with localized inferotemporal optic disc rim defects (ITD). Casuistic and Methods: Fifty-seven eyes of 35 POAG patients were included divided as having ITD (18 eyes) or not (39 eyes). Three different parameters obtained from a spectral domain optic coherence tomography (SD-OCT) [disc-fovea angle (DFA), fóvea vertical deviation (FVD) from midline, and defect\'s angular difference between ITD border and DFA (DAD)] were correlated to four 10-2 VF sectors: superior hemifield, superior edge, nasal edge, and supero nasal arch. Correlations were tested using regression analyses with mixed effects models and random intercepts. Results: Mean (±SD) values of DFA, DAD, and FVD were respectively: -5,0o ± 4.4o, 43.30o ± 17.33o, and -1346.6 µm ± 1609.0 µm. Multiple comparisons showed that in eyes with localized ITD both FVD and DAD, but not DFA, significantly affect the VF sectors. ROC binomial regressions demonstrated that only the 95th percentile cut-off values of FVD (-3264,5 µm) and DAD (70,5o) may influence changes in one (superior edge sensitivity) of the 10-2 VF sectors [FVD: AUC = 0,60 (95% CI = 0,50 - 0,71); DAD: AUC = 0,83 (95%CI = 0,70 - 0,912)]. Conclusions: The vertical fóvea location and its relative positioning to the limits of the ITD impact peripheral 10-2 VF points in the superior hemifield. As DFA itself did not show significant influences in the 10-2 VF, further adjustments using foveal positioning with OCT parameters should be considered in topographical analyses of the central VF in glaucoma patients with localized ITD.

A busca visual é uma habilidade crítica para várias tarefas da vida diária e pode estar prejudicada em pacientes com deficiência visual. O objetivo deste estudo foi comparar a busca visual exploratória entre pacientes com glaucoma primário de ângulo aberto (GPAA) e controles saudáveis, avaliando a correlação espacial entre áreas com perdas localizadas na busca visual exploratória e os defeitos perimétricos, em pacientes com GPAA e com visão normal. Cinquenta e sete indivíduos com visão normal (acuidade visual corrigida melhor que 0.2 logMAR) diagnosticados (grupo GPAA, n = 29) ou não (grupo CONTROL, n = 28) com GPAA, realizaram um exame oftalmológico completo, incluindo perimetria visual (Humphrey -Fast 24.2) e uma tarefa exploratória de busca visual baseada em uma tela com dígitos. Um software personalizado quantificou o (s) tempo (s) gasto (s) até o encontro do número \"4\" em uma matriz aleatória de dígitos distribuídos em cinco áreas, em nove telas sequenciais do programa. Cinco áreas da tela de busca visual foram espacialmente correlacionadas com cinco setores do mapa total deviation (TD) da perimetria visual, após ajustes de ângulo e distância. A análise de covariância (ANCOVA) e testes de correlação foram utilizados para correlacionar parâmetros perimétricos e da busca visual exploratória, por meio de avaliação do tempo individual (gasto para encontrar cada dígito) e tempo total (gasto para completar a tarefa). Os pacientes com GPAA apresentaram pior sensibilidade perimétrica (MD) e de busca visual exploratória do que os controles (MD: -8,02 ± 7,88 dB vs -1,43 ± 1,50 dB; p <0,0001 e tempo total: 106,42 ± 59,64 s vs 52,75 ± 19,07 s; p < 0.0001). A sensibilidade do MD de ambos os grupos correlacionou-se significativamente com o tempo total (GPAA: r = -0.45; p = 0,01 e CONTROL: r = 0,37; p = 0,049). Os testes de ANCOVA mostraram uma correlação significativa entre a busca visual exploratória (tempo individual) e a acuidade visual (P = 0,006) e o diagnóstico de glaucoma (p = 0,005). A sensibilidade média das áreas perimétricas periféricas do grupo GPAA mostrou correlação significativa com o tempo de busca individual nas áreas espaciais correspondentes, exceto na área periférica temporal superior (r = -0,35, p = 0,06). Os controles não mostraram correlação significativa para nenhuma dessas áreas perimétricas, exceto a área periférica temporal superior (r = 0,43, p = 0,02). Com base em nossos resultados, regiões com pior desempenho na busca visual exploratória puderam ser correlacionadas às perdas periféricas localizadas dos pacientes com GPAA. Uma vez que foram estudados pacientes com acuidade visual normal, estes achados destacam a importância do uso de ferramentas de busca visual na avaliação do impacto das perdas perimétricas periféricas em atividades diárias de pacientes com glaucoma. / Visual search is a critical skill for several daily tasks and may be declined in patients with impaired vision. The objectives of this study were to compare the exploratory visual search performance (EVSP) between patients with primary open-angle glaucoma (POAG) and healthy controls, and evaluate the spatial correlation between localized decreases in the EVSP and areas of visual field (VF) loss in normally-sighted patients POAG. Fifty-seven normal vision subjects (best corrected visual acuity better than 0.2 logMAR) diagnosed (POAG group; n= 29) or not (CONTROL group; n= 28) with POAG yielded a complete comprehensive ophthalmological examination, including Humphrey VF tests (SITA-Fast 24.2), and an exploratory visual search digit-based task. A custom software quantified the time (s) spent until patients found the number \"4\" on a random array of digits distributed in five areas on nine sequential screens. Each area was spatially matched with five sectors of the total deviation map from VF, after angle and distance adjustments. Covariance (ANCOVA) and correlation tests were used for correlating VF parameters and EVSP, evaluated through individual time (spent for finding each digit) and total time (spent for completing the task). POAG patients presented worse VF mean deviation (MD) sensitivity and EVSP than controls (MD: -8.02±7.88 dB vs -1.43±1.50 dB; p<0.0001, and total time: 106.42±59.64 s vs 52.75±19.07 s; p<0.0001). MD sensitivity of both groups significantly correlated with total time (POAG: r = -0.45; p = 0.01 and CONTROL: r = 0.37; p = 0.049). ANCOVA tests showed a significant correlation between EVSP (individual time) and both visual acuity (p = 0.006) and glaucoma diagnosis (p = 0.005). The mean sensitivity of the peripheral VF areas of the POAG group showed significant correlation with the individual search time in the corresponding spatial areas, except in the peripheral temporal superior area (r = -0.35, p =0.06). Controls did not show a significant correlation for any of those VF areas, except the peripheral temporal superior area (r =0.43, p =0.02). Based on our results, worse EVSP can be attributable to localized losses in the peripheral VF areas in patients with POAG. Since only normally sighted patients were studied, these findings highlight the importance of using visual search tools to evaluate the impact of peripheral VF loss in daily activities of glaucoma patients, such as driving.

A busca visual é uma habilidade crítica para várias tarefas da vida diária e pode estar prejudicada em pacientes com deficiência visual. O objetivo deste estudo foi comparar a busca visual exploratória entre pacientes com glaucoma primário de ângulo aberto (GPAA) e controles saudáveis, avaliando a correlação espacial entre áreas com perdas localizadas na busca visual exploratória e os defeitos perimétricos, em pacientes com GPAA e com visão normal. Cinquenta e sete indivíduos com visão normal (acuidade visual corrigida melhor que 0.2 logMAR) diagnosticados (grupo GPAA, n = 29) ou não (grupo CONTROL, n = 28) com GPAA, realizaram um exame oftalmológico completo, incluindo perimetria visual (Humphrey -Fast 24.2) e uma tarefa exploratória de busca visual baseada em uma tela com dígitos. Um software personalizado quantificou o (s) tempo (s) gasto (s) até o encontro do número \"4\" em uma matriz aleatória de dígitos distribuídos em cinco áreas, em nove telas sequenciais do programa. Cinco áreas da tela de busca visual foram espacialmente correlacionadas com cinco setores do mapa total deviation (TD) da perimetria visual, após ajustes de ângulo e distância. A análise de covariância (ANCOVA) e testes de correlação foram utilizados para correlacionar parâmetros perimétricos e da busca visual exploratória, por meio de avaliação do tempo individual (gasto para encontrar cada dígito) e tempo total (gasto para completar a tarefa). Os pacientes com GPAA apresentaram pior sensibilidade perimétrica (MD) e de busca visual exploratória do que os controles (MD: -8,02 ± 7,88 dB vs -1,43 ± 1,50 dB; p <0,0001 e tempo total: 106,42 ± 59,64 s vs 52,75 ± 19,07 s; p < 0.0001). A sensibilidade do MD de ambos os grupos correlacionou-se significativamente com o tempo total (GPAA: r = -0.45; p = 0,01 e CONTROL: r = 0,37; p = 0,049). Os testes de ANCOVA mostraram uma correlação significativa entre a busca visual exploratória (tempo individual) e a acuidade visual (P = 0,006) e o diagnóstico de glaucoma (p = 0,005). A sensibilidade média das áreas perimétricas periféricas do grupo GPAA mostrou correlação significativa com o tempo de busca individual nas áreas espaciais correspondentes, exceto na área periférica temporal superior (r = -0,35, p = 0,06). Os controles não mostraram correlação significativa para nenhuma dessas áreas perimétricas, exceto a área periférica temporal superior (r = 0,43, p = 0,02). Com base em nossos resultados, regiões com pior desempenho na busca visual exploratória puderam ser correlacionadas às perdas periféricas localizadas dos pacientes com GPAA. Uma vez que foram estudados pacientes com acuidade visual normal, estes achados destacam a importância do uso de ferramentas de busca visual na avaliação do impacto das perdas perimétricas periféricas em atividades diárias de pacientes com glaucoma. / Visual search is a critical skill for several daily tasks and may be declined in patients with impaired vision. The objectives of this study were to compare the exploratory visual search performance (EVSP) between patients with primary open-angle glaucoma (POAG) and healthy controls, and evaluate the spatial correlation between localized decreases in the EVSP and areas of visual field (VF) loss in normally-sighted patients POAG. Fifty-seven normal vision subjects (best corrected visual acuity better than 0.2 logMAR) diagnosed (POAG group; n= 29) or not (CONTROL group; n= 28) with POAG yielded a complete comprehensive ophthalmological examination, including Humphrey VF tests (SITA-Fast 24.2), and an exploratory visual search digit-based task. A custom software quantified the time (s) spent until patients found the number \"4\" on a random array of digits distributed in five areas on nine sequential screens. Each area was spatially matched with five sectors of the total deviation map from VF, after angle and distance adjustments. Covariance (ANCOVA) and correlation tests were used for correlating VF parameters and EVSP, evaluated through individual time (spent for finding each digit) and total time (spent for completing the task). POAG patients presented worse VF mean deviation (MD) sensitivity and EVSP than controls (MD: -8.02±7.88 dB vs -1.43±1.50 dB; p<0.0001, and total time: 106.42±59.64 s vs 52.75±19.07 s; p<0.0001). MD sensitivity of both groups significantly correlated with total time (POAG: r = -0.45; p = 0.01 and CONTROL: r = 0.37; p = 0.049). ANCOVA tests showed a significant correlation between EVSP (individual time) and both visual acuity (p = 0.006) and glaucoma diagnosis (p = 0.005). The mean sensitivity of the peripheral VF areas of the POAG group showed significant correlation with the individual search time in the corresponding spatial areas, except in the peripheral temporal superior area (r = -0.35, p =0.06). Controls did not show a significant correlation for any of those VF areas, except the peripheral temporal superior area (r =0.43, p =0.02). Based on our results, worse EVSP can be attributable to localized losses in the peripheral VF areas in patients with POAG. Since only normally sighted patients were studied, these findings highlight the importance of using visual search tools to evaluate the impact of peripheral VF loss in daily activities of glaucoma patients, such as driving.

Objetivos: Comparar as alterações de espessura das camadas da retina macular adquiridas com tomografia de coerência óptica (TCO) e as amplitudes das ondas de eletrorretinograma multifocal (ERGmf) convencional e com estímulo lentificado entre olhos com hemianopsia temporal sequelar por compressão quiasmática e controles saudáveis, além de avaliar as correlações entre TCO, ERGmf e campo visual (CV) central. Métodos: Quarenta e três olhos (30 pacientes) com hemianopsia temporal sequelar por tumores hipofisários previamente submetidos a descompressão quiasmática e 37 olhos saudáveis (19 controles) foram submetidos a TCO-DS da mácula, ERGmf e CV tipo 10-2. Após segmentação, foram medidas as espessuras maculares da camada de fibras nervosas da retina (CFNR), camada de células ganglionares (CCG), camada plexiforme interna (CPI), camada nuclear interna (CNI), camada plexiforme externa (CPE), camada nuclear externa (CNE) e camada de fotorreceptores (CFR). Amplitudes e potenciais oscilatórios (PO) multifocais foram adquiridos com o ERGmf convencional e com estímulo lentificado, respectivamente, analisados em valores médios por quadrantes e hemicampos. Resultados: Espessuras da CFNR, CCG e CPI foram significantemente menores em todos os quadrantes, enquanto CNI, CPE e CFR tiveram medidas significantemente maiores nos quadrantes nasais nos pacientes comparados com os controles. Correlações significantes entre a TCO e os valores de CV 10-2 foram positivas para CFNR, CCG e CPI, e negativas para CNI, CPE e CFR. As amplitudes médias dos POs e de N1 do ERGmf se mostraram significantemente reduzidas na hemirretina nasal dos pacientes. Correlações significantes foram encontradas entre as amplitudes de PO e ERGmf para com medidas de TCO da hemirretina nasal interna e externa, respectivamente. Conclusões: Pacientes com hemianopsia temporal sequelar por compressão quiasmática previamente tratada apresentam adelgaçamento significante de CFNR, CCG e CPI e espessamento de CNI, CPE e CFR, associados com amplitudes reduzidas de PO e N1, sugerindo que o dano axonal à retina interna desencadeia lesão secundária das camadas externas da retina nesta condição / Purpose: To compare optical coherence tomography (OCT)-measured macular retinal layers in eyes with permanent temporal hemianopia from chiasmal compression and controls, compare regular and slow-flash multifocal electroretinography (mfERG) in patients and controls, and assess the correlation between OCT, mfERG and central visual field (VF) data. Methods: Forty-three eyes (30 patients) with permanent temporal hemianopia from pituitary tumors previously submitted to chiasm decompression and 37 healthy eyes (19 controls) were submitted to macular SD-OCT, mfERG and 10-2 VF testing. After segmentation, macular retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL) and photoreceptor layer plus (PRL+) thickness was measured. Amplitudes and oscillatory potentials (OP) were measured on regular and slow-flash mfERG, respectively, and expressed as mean values per quadrant and hemifield. Results: RNFL, GCL and IPL thickness measurements were significantly reduced in all quadrants while INL, OPL and PRL were significantly increased in the nasal quadrants in patients compared to controls. Significant correlations between OCT and 10-2 SAP measurements were positive for RNFL, GCL and IPL and negative for INL, OPL and PRL. OPs and mfERG N1 amplitudes were significantly reduced in the nasal hemiretina of patients. Significant correlations were found between OP and mfERG amplitudes for inner and outer nasal hemiretina OCT measurements, respectively. Conclusions: Patients with permanent temporal hemianopia from previously treated chiasmal compression displayed significant RNFL, GCL, IPL thinning and INL, OPL and PRL thickening associated with reduced OP and mfERG N1 amplitudes, suggesting axonal injury to the inner retina leads to secondary damage to the outer retina in this condition

Objetivos: Comparar as alterações de espessura das camadas da retina macular adquiridas com tomografia de coerência óptica (TCO) e as amplitudes das ondas de eletrorretinograma multifocal (ERGmf) convencional e com estímulo lentificado entre olhos com hemianopsia temporal sequelar por compressão quiasmática e controles saudáveis, além de avaliar as correlações entre TCO, ERGmf e campo visual (CV) central. Métodos: Quarenta e três olhos (30 pacientes) com hemianopsia temporal sequelar por tumores hipofisários previamente submetidos a descompressão quiasmática e 37 olhos saudáveis (19 controles) foram submetidos a TCO-DS da mácula, ERGmf e CV tipo 10-2. Após segmentação, foram medidas as espessuras maculares da camada de fibras nervosas da retina (CFNR), camada de células ganglionares (CCG), camada plexiforme interna (CPI), camada nuclear interna (CNI), camada plexiforme externa (CPE), camada nuclear externa (CNE) e camada de fotorreceptores (CFR). Amplitudes e potenciais oscilatórios (PO) multifocais foram adquiridos com o ERGmf convencional e com estímulo lentificado, respectivamente, analisados em valores médios por quadrantes e hemicampos. Resultados: Espessuras da CFNR, CCG e CPI foram significantemente menores em todos os quadrantes, enquanto CNI, CPE e CFR tiveram medidas significantemente maiores nos quadrantes nasais nos pacientes comparados com os controles. Correlações significantes entre a TCO e os valores de CV 10-2 foram positivas para CFNR, CCG e CPI, e negativas para CNI, CPE e CFR. As amplitudes médias dos POs e de N1 do ERGmf se mostraram significantemente reduzidas na hemirretina nasal dos pacientes. Correlações significantes foram encontradas entre as amplitudes de PO e ERGmf para com medidas de TCO da hemirretina nasal interna e externa, respectivamente. Conclusões: Pacientes com hemianopsia temporal sequelar por compressão quiasmática previamente tratada apresentam adelgaçamento significante de CFNR, CCG e CPI e espessamento de CNI, CPE e CFR, associados com amplitudes reduzidas de PO e N1, sugerindo que o dano axonal à retina interna desencadeia lesão secundária das camadas externas da retina nesta condição / Purpose: To compare optical coherence tomography (OCT)-measured macular retinal layers in eyes with permanent temporal hemianopia from chiasmal compression and controls, compare regular and slow-flash multifocal electroretinography (mfERG) in patients and controls, and assess the correlation between OCT, mfERG and central visual field (VF) data. Methods: Forty-three eyes (30 patients) with permanent temporal hemianopia from pituitary tumors previously submitted to chiasm decompression and 37 healthy eyes (19 controls) were submitted to macular SD-OCT, mfERG and 10-2 VF testing. After segmentation, macular retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL) and photoreceptor layer plus (PRL+) thickness was measured. Amplitudes and oscillatory potentials (OP) were measured on regular and slow-flash mfERG, respectively, and expressed as mean values per quadrant and hemifield. Results: RNFL, GCL and IPL thickness measurements were significantly reduced in all quadrants while INL, OPL and PRL were significantly increased in the nasal quadrants in patients compared to controls. Significant correlations between OCT and 10-2 SAP measurements were positive for RNFL, GCL and IPL and negative for INL, OPL and PRL. OPs and mfERG N1 amplitudes were significantly reduced in the nasal hemiretina of patients. Significant correlations were found between OP and mfERG amplitudes for inner and outer nasal hemiretina OCT measurements, respectively. Conclusions: Patients with permanent temporal hemianopia from previously treated chiasmal compression displayed significant RNFL, GCL, IPL thinning and INL, OPL and PRL thickening associated with reduced OP and mfERG N1 amplitudes, suggesting axonal injury to the inner retina leads to secondary damage to the outer retina in this condition

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

Les processus de plasticité cérébrale entrainés par la perte visuelle restent un domaine méconnu dans le champ des neurosciences. La vision centrale et périphérique, le meilleur compromis évolutionniste entre une bonne résolution spatiale et un volume d’espace échantillonné maximal, sont traitées par des régions différentes du cerveau. Par conséquent, étudier et comprendre l’impact de la perte visuelle centrale ou périphérique dans ces régions constitue une étape cruciale dans l’étude du cerveau visuel. Afin d’étudier ces processus, nous avons utilisé deux modèles de perte visuelle sélective de la vision centrale (la dystrophie maculaire de Stargardt) et périphérique (la rétinopathie pigmentaire), et nous avons évalué l’impact à terme de ces deux types de désafférentation sur la structure et la connectivité fonctionnelle du cerveau. 1. Plasticité structurelle induite par la perte sélective de la vision centrale ou périphérique. Nous avons étudié l’épaisseur corticale (EpCo) et de l’entropie corticale (EnCo, marquer de complexité synaptique) du lobe occipital, région pour laquelle nous disposons d’une cartographie complète des régions cytoarchitectoniques. Nous avons constaté que la perte de la vision centrale induit un amincissement des régions appartenant au flux dorsal, tandis que la perte de la vision périphérique occasionne un amincissement du cortex visuel primaire (CVP), ainsi que des régions du flux ventral et dorsal. Ces effets étaient inattendus si on se rapporte au modèle canonique qui associe la vision centrale au flux ventral et la vision périphérique au flux dorsal. La normalité de l’EnCo dans ces régions, suggère que la complexité synaptique est préservée dans les réseaux neuronaux résiduels. Nous avons identifié des modifications de l’EnCo seulement en cas de perte de la vison centrale, où l’augmentation de l’EnCo dans des régions impliquées dans la reconnaissance des objets pourrait traduire une réponse adaptative à la perte de la haute résolution spatiale de cette partie du champ visuel. Cette augmentation de la complexité synaptique pourrait compenser une éventuelle perte neuronale et être responsable de la normalité de l’EpCo dans ces régions. 2. Plasticité de la connectivité fonctionnelle des régions du cortex visuel primaire recevant les projections de la partie centrale » et périphérique champ visuel Dans cette étude, nous avons exploré et comparé la connectivité fonctionnelle des régions afférentées et desafférentées du CVP de sujets souffrant de dystrophie maculaire de Stargardt et retinitis pigmentosa, avec les régions afféréntées correspondantes du CVP de sujets avec une vision normale. Cette étude a révélé une réorganisation fonctionnelle distincte du CVP afférenté et désafférenté. Ainsi, le CVP qui reçoit les afférences visuelles résiduelles présente une connectivité fonctionnelle accrue avec des régions voisines, probablement afin de favoriser le traitement de l’information visuelle, tandis que le CVP désafférenté augmente sa connectivité fonctionnelle avec des régions plus éloignées, vraisemblablement pour contribuer aux fonctions supérieures et à des processus de type top-down. L’analyse comparative des données morphologiques et fonctionnelles suggère une correspondance des régions amincies du cortex visuel associatif avec des régions qui montrent une diminution de la connectivité fonctionnelle avec le CVP périphérique, et des régions présentant une augmentation de la complexité synaptique avec des régions qui montrent une connectivité fonctionnelle accrue avec le CVP périphérique. Ces données suggèrent que la désafferentation sensorielle du CVP périphérique est plus propice au développement d’une réorganisation cérébrale. Synoptique : Ces travaux révèlent un aspect inattendu de la plasticité cérébrale induite une perte isolée de la vision centrale ou périphérique. La réorganisation s’avère plus complexe que le laisser présager le modèle canonique actuel, vraisemblablement trop simple. / Cerebral plasticity induced by visual loss represents a poorly understood field of neuroscience, with numerous questions that don’t yet have an answer. Central and peripheral vision, the evolutionary compromise between spatial resolution and the sampled space volume, are processed in distinct areas of the brain. Understanding the impact of vision loss in theses regions, is of utmost interest for the study of visual brain. Herein, in two models of retinal disorders affecting central and peripheral vision (namely Stargardt macular dystrophy and retinitis pigmentosa), we specifically investigated the effects of the central and peripheral visual loss on brain morphology and its functional connectivity. 1. Morphological plastic changes induced by central and peripheral visual loss. We explored the effects of visual loss on cortical thickness (CoTks) and cortical entropy (CoEn, marker of synaptic complexity) in the cytoarchytectonic regions of the occipital lobe. Central visual loss associated thinning in dorsal stream regions, while peripheral visual loss in early visual cortex (EVC) and regions belonging both to dorsal and ventral stream. Theses effects were unpredicted by the canonical view “central vision – ventral stream”, “peripheral vision – dorsal stream”. Normal CoEn in theses areas suggests that synaptic complexity is preserved in the remaining networks. Only central visual field loss presented CoEn alterations, namely an increase in areas involved in object recognition, that likely reflects a synaptic complexity enhancement in response to the loss of the high spatial resolution of central vision. The gain in synaptic complexity could mask neuronal loss due to deafferentation and may account for the CoTks normality. 2. Plastic changes in the functional connectivity of central and peripheral EVC. We explored and compared to normally afferented EVC, the functional connectivity of afferented and deafferented parts of EVC and found that central and peripheral visual loss induce different patterns of reorganization. Residually afferented early visual cortex reinforce local connections presumably to enhance the processing of altered visual input, while deafferented EVC strengthen long-range connections presumably to assist high-order functions. Combined structural and functional data indicate that areas with reduced CoTks superpose with several areas presenting reduced functional connectivity with the peripheral EVC and that areas with increased CoEn superpose with several areas presenting increased functional connectivity with afferented peripheral EVC. These data point that alterations of the sensory input to the peripheral field are more prone to induce plastic changes. Overview : Data in the current work provide an interesting perspective about the plasticity following central or peripheral visual field loss and show that it is more complex than the canonical model would have let to presume.

Abstract Glaucoma is a group of eye diseases characterized by a chronic, progressive optic neuropathy. During the disease process, the axon damage of the retinal ganglion cells leads to changes in the retinal nerve fiber layer, causing optic nerve head, and visual field defects typical of glaucoma. The Heidelberg Retina Tomograph (HRT) is a confocal scanning laser imaging device acquiring and analysing three-dimensional data of the ocular fundus wit good accuracy and reproducibility. Conventional planimetric measurements were compared to those taken with the HRT in a pilot study of 12 eyes with early glaucomatous optic disc, retinal nerve fiber layer and/or visual field abnormalities. The neuroretinal rim area measurements and cup-to-disc area ratio did not differ statistically from each other when using these two different methods. The effect of four different reference levels on the HRT parameter measurement values was tested in two separate studies. In the first study there were 67 eyes, 40 of the eyes were healthy and 27 eyes had glaucoma of different stages. Then, 279 eyes, 180 of which were non-glaucomatous and 99 glaucoma eyes, were included in another study. The flexible reference level gave the most reliable HRT parameter measurement values in both non-glaucomatous and glaucomatous eyes. The ability of the HRT parameters to separate between non-glaucomatous and glaucomatous eyes was tested in 77 eyes, 40 of the eyes were non-glaucomatous, 10 ocular hypertensives and 27 eyes had different stages of glaucoma. The reference level dependent HRT parameters cup-to-disc area ratio, vertical linear cup-to-disc ratio, mean retinal nerve fiber layer thickness (RNFLt) and rim volume as well as the reference level non-dependent HRT parameter, cup shape measure (CSM), separated best between the clinical groups. The best combination of the HRT and other structural and functional parameters in separating between non-glaucomatous and glaucomatous eyes was studied in 55 eyes. There were 32 non-glaucomatous eyes and 23 eyes with ocular hypertension or glaucoma. CSM, RNFLt, together with age- and lens coloration-corrected mean deviation of the B/Y perimetry showed good discrimination (ROC area 0.91) between non-glaucomatous and glaucomatous eyes. / Tiivistelmä Glaukooma koostuu joukosta hitaasti eteneviä näköhermon rappeumasairauksia. Sairausprosessin aikana verkkokalvon gangliosolujen aksonivaurio johtaa muutoksiin verkkokalvon hermosäiekerroksessa ja näköhermon päässä aiheuttaen glaukoomalle tyypillisiä näkökenttämuutoksia. The Heidelberg Retina Tomograph (HRT) on konfokaali laserskanneritekniikkaan perustuva kuvantamislaite, joka tuottaa ja analysoi silmänpohjasta saatua kolmiulotteista mittaustietoa tarkasti ja toistettavasti. Tavanomaisen planimetrian antamia mittaustuloksia verrattiin HRT:n antamiin tuloksiin 12:ssa silmässä, joissa oli todettu varhaisia glaukoomamuutoksia. Näköhermon pään hermoreunan (rim) pinta-ala ja keskuskuopan suhde papillan läpimittaan eivät poikenneet tilastollisesti toisistaan näitä kahta menetelmää käytettäessä. Neljän eri referenssitason vaikutusta HRT-parametrien mittausarvoihin testattiin kahdessa eri tutkimuksessa. Ensimmäisen tutkimusaineisto koostui yhteensä 67:stä silmästä, joista 40 oli terveitä ja 27:ssä eriasteisia glaukoomamuutoksia. Toisessa tutkimuksessa oli yhteensä 279 silmää, joista 180 oli terveitä ja 99:llä oli glaukooma. Papillomakulaarisäikeisiin tukeutuva, fleksiibeli referenssitaso antoi luotettavimmat HRT-parametrien mittaustulokset sekä terveissä että glaukoomasilmissä. HRT-parametrien kykyä erottaa terveet silmät glaukomatoottisista testattiin yhteensä 77:ssä silmässä, joista 40 oli terveitä, 10 oli korkeapaineisia ilman glaukoomamuutoksia, ja 27:ssä oli glaukoomamuutoksia. Referenssitasosta riippuvaiset HRT-parametrit, keskuskuopan suhde papillan läpimittaan, vertikaali-lineaarinen keskuskuopan suhde papillan läpimittaan, keskimääräinen verkkokalvon hermosäiekerroksen paksuus (RNFLt) ja `rim´:in tilavuus samoin kuin referenssitasosta riippumaton keskuskuopan ´vinous´-mitta (CSM) erottelivat parhaiten nämä kliiniset ryhmät toisistaan. Terveitä ja glaukoomasilmiä erottelevaa HRT:n ja muiden rakenteellisten ja toiminnallisten parametrien kombinaatiota etsittiin 55:n silmän aineistosta. Silmistä 32 oli terveitä ja 23 korkeapaineisia ja/tai glaukoomavaurioisia. CSM ja RNFLt, yhdessä iän ja mykiövärjäytymisen suhteen korjatun sinikeltaperimetrian keskipoikkeaman kanssa osoittivat hyvää erottelukykyä (ROC area 0.91) terveiden ja glaukoomasilmien välillä.