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Ganglion cell and optic nerve physiology in health and disease: the role of novel psychophysical and electrophysiological techniques; Fisiologia das células e do nervo óptico na saúde e na doença: o papel das novas metodologias psicofísicas e electrofisiológicas

Reis, Aldina Susana Aragônes da Conceição Pires
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Tese de Doutorado
POR
Relevância na Pesquisa
16.76%
As células ganglionares (CG) têm um papel preponderante no processamento da Visão, dadas as suas características estruturais e funcionais. As diferenças anatómicas destas células imprimem uma variedade de mosaicos e circuitos neuronais que estão na base de diferentes vias visuais. Esta especificidade começa na retina e estende-se até ao córtex visual através de vias retinocorticais paralelas, de acordo com as propriedades funcionais intrínsecas dos seus neurónios. As células do sistema parvocelular são pequenas (originando campos receptores pequenos) e especializadas no processamento da informação cromática (eixo vermelho-verde), apresentando alta resolução espacial e baixa resolução temporal, contrariamente às do sistema magnocelular, que são maiores (com campos receptores igualmente de maiores dimensões). A via magnocelular apresenta elevada sensibilidade ao contraste para estímulos dinâmicos de baixa frequência espacial. O sistema coniocelular é constituído por células biestratificadas, com propriedades espaciais e temporais intermédias comparativamente às das outras vias retinocorticais, sendo sensível ao contraste cromático no eixo azul-amarelo. Diferentes mecanismos de doença, intrinsecamente relacionados com patologias da retina e do nervo óptico...

Tool manipulation knowledge is retrieved by way of the ventral visual object processing pathway

Almeida, Jorge; Fintzi, Anat R.; Mahon, Bradford Z.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
16.76%
Using functional Magnetic Resonance Imaging (fMRI), we find that object manipulation knowledge is accessed by way of the ventral object processing pathway. We exploit the fact that parvocellular channels project to the ventral but not the dorsal stream, and show that increased neural responses for tool stimuli are observed in the inferior parietal lobule when those stimuli are visible only to the ventral object processing stream. In a control condition, tool-preferences were observed in a superior and posterior parietal region for stimuli titrated so as to be visible by the dorsal visual pathway. Functional connectivity analyses confirm the dissociation between sub-regions of parietal cortex according to whether their principal afferent input is via the ventral or dorsal visual pathway. These results challenge the ‘Embodied Hypothesis of Tool Recognition’, according to which tool identification critically depends on simulation of object manipulation knowledge. Instead, these data indicate that retrieval of object-associated manipulation knowledge is contingent on accessing the identity of the object, a process that is subserved by the ventral visual pathway.

Chromatic discrimination losses in multiple sclerosis patients with and without optic neuritis using the Cambridge Colour Test

MOURA, Ana Laura De Araujo; TEIXEIRA, Rosani Aparecida Antunes; OIWA, Nestor N.; COSTA, Marcelo F.; FEITOSA-SANTANA, Claudia; CALLEGARO, Dagoberto; HAMER, Russell D.; VENTURA, Dora Fix
Fonte: CAMBRIDGE UNIV PRESS Publicador: CAMBRIDGE UNIV PRESS
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
16.76%
We assessed chromatic discrimination in multiple sclerosis (MS) patients both with (ON) and without (no ON) a history of optic neuritis using the Cambridge color test (CCT). Our goal was to determine the magnitude and chromatic axes of any color vision losses in both patient groups, and to evaluate age-related changes in chromatic discrimination in both patient groups compared to normals. Using the CCT, we measured chromatic discrimination along the protan, deutan and tritan axes in 35 patients with MS (17 ON eyes) and 74 age matched controls. Color thresholds for both patient groups were significantly higher than controls` along the protan and tritan axes (P < 0.001). In addition, the ON and no-ON groups differed significantly along all three-color axes (p < 0.001). MS patients presented a progressive color discrimination impairment with age (along the deutan and tritan axes) that was almost two times faster than controls, even in the absence of ON. These findings suggest that demyelinating diseases reduce sensitivity to color vision in both red-green and blue-yellow axes, implying impairment in both parvocellular and koniocellular visual pathways. The CCT is a useful tool to help characterize vision losses in MS and the relationship between these losses and degree of optic nerve involvement.

Estudo da visão de cores, percepção de formas e espaço em pacientes com esclerose múltipla; Study of color vision, perception of shapes and space in patients with multiple sclerosis

Teixeira, Rosani Aparecida Antunes
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 27/02/2008 PT
Relevância na Pesquisa
16.76%
A presente dissertação objetiva avaliar a visão de cores dos pacientes com EM (com e sem queixas visuais), através de teste psicofísicos e a percepção de formas e espaço, através de testes neuropsicológicos, além de investigar a existência de correlação entre essas funções. Participaram da pesquisa um total de 35 pacientes (9 M e 27 F) com o diagnóstico de EM, com idades entre 18 e 60 anos (média 36,84±10,49), e nível de educação variado, e 36 controles com faixa etária e nível escolar equivalente. Os pacientes possuíam acuidade visual 20/20, ou melhor e foram divididos em dois grupos: um com neurite óptica (NO n=52) outro sem NO (n=17). Foram utilizados os testes: Cambridge Color Test (CCT) fase trivector e elipse, Judgment of line orientation (JLO), visual form discrination (VFD), Bateria de percepção visual de objeto e espaço (VOSP), e as Escalas de depressão e ansiedade de Beck. Os resultados mostram diferenças entre grupos (anova OneWay), nos três eixos analisados (protan, deutan e tritan) e nas áreas das elipses em todos os grupos, (p0,005) indicando que a visão de cores está prejudicada em ambos os sistemas de oponência, sendo que a ocorrência de NO está associada a maior prejuízo, mas há perda da visão de cores mesmo na ausência de NO. Dos olhos sem NO 52% possui áreas das elipses normais (27/52)...

Structure and function of parallel pathways in the primate early visual system

Callaway, Edward M
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
16.76%
Parallel processing streams in the primate visual system originate from more than a dozen anatomically and functionally distinct types of retinal ganglion cells (RGCs). A central problem in determining how visual information is processed is understanding how each of these RGC types connects to more central structures, including the lateral geniculate nucleus (LGN) of the thalamus and (via the LGN) the primary visual cortex. Neverthelss, the available functional and anatomical evidence linking together specific cell types across these structures is surprisingly indirect. This review evaluates the available evidence and assesses the strength of the many inferences that can be made from these observations. There is strong evidence that parasol RGCs are the provenance of the magnocellular (M) visual pathway and that midget RGCs give rise to the parvocellular (P) pathway. Furthermore, the M and P pathways remain segregated up to the input layer of primary visual cortex. The relationships between the numerous other RGC types and cell types in the LGN remain less certain. and there remains ambiguity about how best to define additional pathways, such as the koniocellular (K) pathway, which probably arise from these other, less common, RGC types.

Geniculocortical relay of blue-off signals in the primate visual system

Szmajda, Brett A.; Buzás, Péter; FitzGibbon, Thomas; Martin, Paul R.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
17.98%
A fundamental dichotomy in the subcortical visual system exists between on- and off-type neurons, which respectively signal increases and decreases of light intensity in the visual environment. In primates, signals for red-green color vision are carried by both on- and off-type neurons in the parvocellular division of the subcortical pathway. It is thought that on-type signals for blue-yellow color vision are carried by cells in a distinct, diffusely projecting (koniocellular) pathway, but the pathway taken by blue-off signals is not known. Here, we measured blue-off responses in the subcortical visual pathway of marmoset monkeys. We found that the cells exhibiting blue-off responses are largely segregated to the koniocellular pathway. The blue-off cells show relatively large receptive fields, sluggish responses to maintained contrast, little sign of an inhibitory receptive-field surround mechanism, and negligible functional input from an intrinsic (melanopsin-based) phototransductive mechanism. These properties are consistent with input from koniocellular or “W-like” ganglion cells in the retina and suggest that blue-off cells, as previously shown for blue-on cells, could contribute to cortical mechanisms for visual perception via the koniocellular pathway.

Response variability of marmoset parvocellular neurons

Victor, J D; Blessing, E M; Forte, J D; Buzás, P; Martin, P R
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
16.76%
This study concerns the properties of neurons carrying signals for colour vision in primates. We investigated the variability of responses of individual parvocellular lateral geniculate neurons of dichromatic and trichromatic marmosets to drifting sinusoidal luminance and chromatic gratings. Response variability was quantified by the cycle-to-cycle variation in Fourier components of the response. Averaged across the population, the variability at low contrasts was greater than predicted by a Poisson process, and at high contrasts the responses were approximately 40% more variable than responses at low contrasts. The contrast-dependent increase in variability was nevertheless below that expected from the increase in firing rate. Variability falls below the Poisson prediction at high contrast, and intrinsic variability of the spike train decreases as contrast increases. Thus, while deeply modulated responses in parvocellular cells have a larger absolute variability than weakly modulated ones, they have a more favourable signal: noise ratio than predicted by a Poisson process. Similar results were obtained from a small sample of magnocellular and koniocellular (‘blue-on’) neurons. For parvocellular neurons with pronounced colour opponency...

Temporal contrast sensitivity in the lateral geniculate nucleus of a New World monkey, the marmoset Callithrix jacchus

Solomon, Samuel G; White, Andrew J R; Martin, Paul R
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Publicado em 15/06/1999 EN
Relevância na Pesquisa
18.12%
The temporal contrast sensitivity of koniocellular, parvocellular and magnocellular cells in the lateral geniculate nucleus (LGN) of nine adult marmosets was measured. The receptive fields of the cells were between 0.3 and 70 deg from the fovea. The stimulus was a large spatially uniform field which was modulated in luminance at temporal frequencies between 0.98 and 64 Hz.For each cell group there was a gradual increase in modulation sensitivity, especially for temporal frequencies below 8 Hz, with increasing distance from the fovea. At any given eccentricity, magnocellular cells had the greatest sensitivity. In central visual field, the sensitivity of koniocellular cells lay between that of parvocellular and magnocellular cells. In peripheral visual field (above 10 deg eccentricity) koniocellular and parvocellular cells had similar sensitivity.The contrast sensitivity of each cell class was dependent on the anaesthetic used. Cells from animals anaesthetized with isoflurane were less sensitive than cells from animals anaesthetized with sufentanil. This effect was more marked for temporal frequencies below 4 Hz.These results are incompatible with the notion that the koniocellular pathway is functionally homologous to a sluggish, W-like pathway in other mammals. At least in terms of their temporal transfer properties...

A comparison of koniocellular, magnocellular and parvocellular receptive field properties in the lateral geniculate nucleus of the owl monkey (Aotus trivirgatus)

Xu, Xiangmin; Ichida, Jennifer M; Allison, John D; Boyd, Jamie D; Bonds, A B; Casagrande, Vivien A
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Publicado em 15/02/2001 EN
Relevância na Pesquisa
27.42%
By analogy to previous work on lateral geniculate nucleus (LGN) magnocellular (M) and parvocellular (P) cells our goal was to construct a physiological profile of koniocellular (K) cells that might be linked to particular visual perceptual attributes.Extracellular recordings were used to study LGN cells, or their axons, in silenced primary visual cortex (V1), in nine anaesthetized owl monkeys injected with a neuromuscular blocker. Receptive field centre–surround organization was examined using flashing spots. Spatial and temporal tuning and contrast responses were examined using drifting sine-wave gratings; counterphase sine-wave gratings were used to examine linearity of spatial summation.Receptive fields of 133 LGN cells and 10 LGN afferent axons were analysed at eccentricities ranging from 2.8 to 31.3 deg. Thirty-four per cent of K cells and only 9 % of P and 6 % of M cells responded poorly to drifting gratings. K, P and M cells showed increases in centre size with eccentricity, but K cells showed more scatter. All cells, except one M cell, showed linearity in spatial summation.At matched eccentricities, K cells exhibited lower spatial and intermediate temporal resolution compared with P and M cells. K contrast thresholds and gains were more similar to those of M than P cells. M cells showed lower spatial and higher temporal resolution and contrast gains than P cells.K cells in different K LGN layers differed in spatial...

Spatial properties of koniocellular cells in the lateral geniculate nucleus of the marmoset Callithrix jacchus

White, Andrew J R; Solomon, Samuel G; Martin, Paul R
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Publicado em 01/06/2001 EN
Relevância na Pesquisa
27.42%
The receptive field dimensions, contrast sensitivity and linearity of spatial summation of koniocellular (KC), parvocellular (PC) and magnocellular (MC) cells in the lateral geniculate nucleus (LGN) of 11 adult marmosets were measured using achromatic sinusoidal gratings.The receptive field centre diameter of cells in each (PC, KC and MC) class increases with distance from the fovea. There is substantial overlap in centre size between the three cell classes at any eccentricity, but the PC cells have, on average, the smallest centres and the KC cells have the largest. Some PC and KC cells did not respond at all to the grating stimulus.The contrast sensitivity of the receptive field centre mechanism in KC cells decreases in proportion to the centre area. A similar trend was seen for the surround mechanism. These characteristics are common to PC and MC cells, suggesting that they originate at an early stage of visual processing in the retina.The KC cells showed, in general, lower peak evoked discharge rates than PC or MC cells. The spontaneous discharge rate of KC cells was lower than that of PC cells and similar to that of MC cells.The majority of cells in all divisions of the LGN show linear spatial summation. A few cells did show non-linear spatial summation; these cells were predominantly located in the MC and ventral KC layers.The ventral KC layers below and between the MC layers contain cells with larger and more transiently responding receptive fields than cells in the more dorsal KC layers.We conclude that many of the contrast-dependent spatial properties of cells in the marmoset LGN are common to PC...

Molecular Correlates of Laminar Differences in the Macaque Dorsal Lateral Geniculate Nucleus

Murray, Karl D.; Rubin, Carol M.; Jones, Edward G.; Chalupa, Leo M.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 12/11/2008 EN
Relevância na Pesquisa
16.76%
In anthropoid primates, cells in the magnocellular and parvocellular layers of the dorsal lateral geniculate nucleus (dLGN) are distinguished by unique retinal inputs, receptive field properties and laminar terminations of their axons in visual cortex. To identify genes underlying these phenotypic differences, we screened RNA from magnocellular and parvocellular layers of adult macaque dLGN for layer-specific differences in gene expression. Real time quantitative RT-PCR and in situ hybridization were used to confirm gene expression in adult and fetal macaque. Cellular localization of gene expression revealed eleven new layer-specific markers, of which ten were enriched in magnocellular layers (BRD4, CAV1, EEF1A2, FAM108A1, INα, KCNA1, NEFH, NEFL, PPP2R2C, and SFRP2) and one was enriched in parvocellular and koniocellular layers (TCF7L2). These markers relate to functions involved in development, transcription and cell signaling, with Wnt/β-catenin and neurofilament pathways figuring prominently. A subset of markers was differentially expressed in the fetal dLGN during a developmental epoch critical for magno- and parvocellular pathway formation. These results provide new evidence for the molecular differentiation of magnocellular and parvocellular streams through the primate dLGN.

Segregation of short-wavelength-sensitive (S) cone signals in the macaque dorsal lateral geniculate nucleus

Roy, Sujata; Jayakumar, Jaikishan; Martin, Paul R; Dreher, Bogdan; Saalmann, Yuri B; Hu, Daping; Vidyasagar, Trichur R
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
Publicado em /10/2009 EN
Relevância na Pesquisa
17.76%
An important problem in the study of the mammalian visual system is whether functionally different retinal ganglion cell types are anatomically segregated further up along the central visual pathway. It was previously demonstrated that, in a New World diurnal monkey (marmoset), the neurones carrying signals from the short-wavelength-sensitive (S) cones [blue–yellow (B/Y)-opponent cells] are predominantly located in the koniocellular layers of the dorsal lateral geniculate nucleus (LGN), whereas the red–green (R/G)-opponent cells carrying signals from the medium- and long-wavelength-sensitive cones are segregated in the parvocellular layers. Here, we used extracellular single-unit recordings followed by histological reconstruction to investigate the distribution of color-selective cells in the LGN of the macaque, an Old World diurnal monkey. Cells were classified using cone-isolating stimuli to identify their cone inputs. Our results indicate that the majority of cells carrying signals from S-cones are located either in the koniocellular layers or in the ‘koniocellular bridges’ that fully or partially span the parvocellular layers. By contrast, the R/G-opponent cells are located in the parvocellular layers. We conclude that anatomical segregation of B/Y- and R/G-opponent afferent signals for color vision is common to the LGNs of New World and Old World diurnal monkeys.

Retinal Afferents Synapse with Relay Cells Targeting the Middle Temporal Area in the Pulvinar and Lateral Geniculate Nuclei

Warner, Claire E.; Goldshmit, Yona; Bourne, James A.
Fonte: Frontiers Research Foundation Publicador: Frontiers Research Foundation
Tipo: Artigo de Revista Científica
Publicado em 12/02/2010 EN
Relevância na Pesquisa
17.42%
Considerable debate continues regarding thalamic inputs to the middle temporal area (MT) of the visual cortex that bypass the primary visual cortex (V1) and the role they might have in the residual visual capability following a lesion of V1. Two specific retinothalamic projections to area MT have been speculated to relay through the medial portion of the inferior pulvinar nucleus (PIm) and the koniocellular layers of the dorsal lateral geniculate nucleus (LGN). Although a number of studies have demonstrated retinal inputs to regions of the thalamus where relays to area MT have been observed, the relationship between the retinal terminals and area MT relay cells has not been established. Here we examined direct retino-recipient regions of the marmoset monkey (Callithrix jacchus) pulvinar nucleus and the LGN following binocular injections of anterograde tracer, as well as area MT relay cells in these nuclei by injection of retrograde tracer into area MT. Retinal afferents were shown to synapse with area MT relay cells as demonstrated by colocalization with the presynaptic vesicle membrane protein synaptophysin. We also established the presence of direct synapes of retinal afferents on area MT relay cells within the PIm, as well as the koniocellular K1 and K3 layers of the LGN...

Slow intrinsic rhythm in the koniocellular visual pathway

Cheong, Soon Keen; Tailby, Chris; Martin, Paul R.; Levitt, Jonathan B.; Solomon, Samuel G.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.42%
Slow rhythmic changes in nerve-cell activity are characteristic of unconscious brain states and also may contribute to waking brain function by coordinating activity between cortical and subcortical structures. Here we show that slow rhythms are exhibited by the koniocellular (K) pathway, one of three visual pathways beginning in the eye and projecting through the lateral geniculate visual relay nucleus to the cerebral cortex. We recorded activity in pairs and ensembles of neurons in the lateral geniculate nucleus of anesthetized marmoset monkeys. We found slow rhythms are common in K cells but are rare in parvocellular and magnocellular cell pairs. The time course of slow K rhythms corresponds to subbeta (<10 Hz) EEG frequencies, and high spike rates in K cells are associated with low power in the theta and delta EEG bands. By contrast, spontaneous activity in the parvocellular and magnocellular pathways is neither synchronized nor strongly linked to EEG state. These observations suggest that parallel visual pathways not only carry different kinds of visual signals but also contribute differentially to brain circuits at the first synapse in the thalamus. Differential contribution of sensory streams to rhythmic brain circuits also raises the possibility that sensory stimuli can be tailored to modify brain rhythms.

Colour and pattern selectivity of receptive fields in superior colliculus of marmoset monkeys

Tailby, Chris; Cheong, Soon Keen; Pietersen, Alexander N; Solomon, Samuel G; Martin, Paul R
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
17.76%
The main subcortical visual targets of retinal output neurones (ganglion cells) are the parvocellular and magnocellular layers of the dorsal lateral geniculate nucleus (LGN) in the thalamus. In addition, a small and heterogeneous collection of ganglion cell axons projects to the koniocellular layers of the LGN, to the superior colliculus (SC), and to other subcortical targets. The functional (receptive field) properties and target specificity of these non-parvocellular, non-magnocellular populations remain poorly understood. It is known that one population of koniocellular layer cells in the LGN (blue-On cells) receives dominant functional input from short-wavelength sensitive (S or ‘blue’) cones. Here we asked whether SC neurones also receive S cone inputs. We made extracellular recordings from single neurones (n = 38) in the SC of anaesthetised marmoset monkeys. Responses to drifting and flashed gratings providing defined levels of cone contrast were measured. The SC receptive fields we recorded were often binocular, showed ‘complex cell’ like responses (On–Off responses), strong bandpass spatial frequency tuning, direction selectivity, and many showed strong and rapid habituation to repeatedly presented stimuli. We found no evidence for dominant S cone input to any SC neurone recorded. These data suggest that S cone signals may reach cortical pathways for colour vision exclusively through the koniocellular division of the lateral geniculate nucleus.

Topography of the frequency doubling perimetry visual field compared with that of short wavelength and achromatic automated perimetry visual fields

Landers, J.; Sharma, A.; Goldberg, I.; Graham, S.
Fonte: British Med Journal Publ Group Publicador: British Med Journal Publ Group
Tipo: Artigo de Revista Científica
Publicado em //2006 EN
Relevância na Pesquisa
17.42%
Background: Traquair described the topography of visual field sensitivity as a "hill" or "island" of vision. Achromatic automated perimetry (AAP) demonstrates this shape of the visual field in photopic conditions. Techniques claimed to target the magnocellular pathway (frequency doubling perimetry, FDP) and those using a stimulus targeting the koniocellular pathway (short wavelength (or blue on yellow) automated perimetry, SWAP), might produce one that is different. The authors compared the visual field topography from FDP with those of SWAP and AAP, to investigate whether there were significant differences in their shape. Method: A sample of 51 patients with previously confirmed normal perimetry were recruited; either low risk glaucoma suspects or normal controls. AAP, SWAP, and FDP perimetry was performed in random order on the same day. The topography of each field was analysed to determine its average shape and to compare results in the same individuals. Results: The topography of the visual field produced by each perimeter differed significantly. While all three had maximal sensitivity centrally, over the 24 degrees from the centre to the periphery, mean sensitivities decreased by 4.9 decibels (dB) for AAP and 7.3 dB for SWAP...

Novos biomarcadores no glaucoma e neuropatias ópticas hereditárias: implicações para o diagnóstico precoce e monitorização da evolução clínica; Pathophysiological mechanisma and novel biomarkers in acquired and genetic diseases of the retinal ganglion cell

Mateus, Catarina Andreia Domingues
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
17.42%
As células ganglionares da retina (CG) têm um papel fundamental no processamento da informação até ao córtex visual, conforme evidenciam as suas características específicas morfológicas e funcionais. A lesão das CG constitui a base da patogénese de algumas doenças da retina e do nervo óptico. Assim, esta tese centra-se na identificação de novos biomarcadores de lesão em doenças adquiridas e genéticas das CG, nomeadamente na Neuropatia Óptica Glaucomatosa e na Neuropatia Óptica Hereditária de Leber (NOHL). Deste modo, aplicámos um conjunto de métodos funcionais e estruturais, inovadores e convencionais, com o objectivo de comparar mecanismos patofisiológicos de lesão em dois grupos diferentes de pacientes, correspondendo a dois modelos de doença das CG: 1) modelo de neuropatia óptica hereditária, 15 portadores assintomáticos de NOHL com mutação mtDNA 11778G>A, pertencentes a duas gerações do mesmo pedigree; 2) modelo de neuropatia óptica adquirida, 52 participantes provindos da consulta de Glaucoma, divididos nos seguintes grupos: hipertensão ocular (n=18 olhos), suspeitos de glaucoma (n=15 olhos) e glaucoma primário de ângulo aberto (n=19 olhos). Os dados obtidos foram comparados com dois grupos de controlos ajustados à idade e ao género. Relativamente aos portadores assintomáticos de NOHL...

Independent patterns of damage within magno-, parvo- and koniocellular pathways in Parkinson's disease

Silva, M. F.; Faria, P.; Regateiro, F. S.; Forjaz, V.; Januário, C.; Freire, A.; Castelo-Branco, M.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
38.22%
Sensory deficits have been documented in Parkinson's disease, in particular within the visual domain. However, ageing factors related to the brain and to neural and non-neural ocular structures could explain some of the previously reported results, in particular the claimed impairment within the koniocellular pathway. This study addressed visual impairment attributable to the magno- (luminance), parvo- (red-green) and koniocellular (blue-yellow) pathways in a population of Parkinson's disease patients. To avoid potentially confounding factors, all subjects underwent a full neurophthalmological assessment which led to exclusion of subjects with increased intraocular pressure, diabetes even in the absence of retinopathy, and ocular abnormalities (from a total of 72 patients' eyes, 12 were excluded). Both parvo- and koniocellular pathways were studied by means of contrast sensitivity (CS) measurements along protan, tritan and deutan axes and also by fitting chromatic discrimination ellipses using eight measured contrast axes. Magnocellular function was assessed, using stimuli that induce a frequency doubling illusion, in 17 locations in the fovea and periphery. Achromatic (luminance modulation) thresholds were significantly higher in Parkinson's disease both in foveal and peripheral locations. A significant impairment was observed along protan and deutan axes...

Independent patterns of damage within magno-, parvo- and koniocellular pathways in Parkinson's disease

Silva, MF; Regateiro, FS; Forjaz, V; Januário, C; Freire-Gonçalves, A; Castelo-Branco, M
Fonte: Centro Hospitalar e Universitário de Coimbra Publicador: Centro Hospitalar e Universitário de Coimbra
Tipo: Artigo de Revista Científica
Publicado em //2005 ENG
Relevância na Pesquisa
28.12%
Sensory deficits have been documented in Parkinson's disease, in particular within the visual domain. However, ageing factors related to the brain and to neural and non-neural ocular structures could explain some of the previously reported results, in particular the claimed impairment within the koniocellular pathway. This study addressed visual impairment attributable to the magno- (luminance), parvo- (red-green) and koniocellular (blue-yellow) pathways in a population of Parkinson's disease patients. To avoid potentially confounding factors, all subjects underwent a full neurophthalmological assessment which led to exclusion of subjects with increased intraocular pressure, diabetes even in the absence of retinopathy, and ocular abnormalities (from a total of 72 patients' eyes, 12 were excluded). Both parvo- and koniocellular pathways were studied by means of contrast sensitivity (CS) measurements along protan, tritan and deutan axes and also by fitting chromatic discrimination ellipses using eight measured contrast axes. Magnocellular function was assessed, using stimuli that induce a frequency doubling illusion, in 17 locations in the fovea and periphery. Achromatic (luminance modulation) thresholds were significantly higher in Parkinson's disease both in foveal and peripheral locations. A significant impairment was observed along protan and deutan axes...

Retinotopic distribution of chromatic responses in human primary visual cortex

Vanni, S; Henriksson, L.; Viikari, M; James, Andrew
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.42%
In non-human primates at least three anatomically and functionally distinct channels convey signals from the retina to the primary visual cortex (V1). Two of these channels, the parvocellular and the koniocellular, are sensitive to chromatic contrasts and