The Experts below are selected from a list of 22008 Experts worldwide ranked by ideXlab platform
Aleksandra S. Dain - One of the best experts on this subject based on the ideXlab platform.
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patterns of individual variation in Visual Pathway structure and function in the sighted and blind
PLOS ONE, 2016Co-Authors: G.k. Aguirre, Omar H. Butt, Kate E Watkins, Holly Bridge, Ritobrato Datta, Noah C. Benson, Artur V Cideciyan, Sashank Prasad, Samuel G Jacobson, Aleksandra S. DainAbstract:Many structural and functional brain alterations accompany blindness, with substantial individual variation in these effects. In normally sighted people, there is correlated individual variation in some Visual Pathway structures. Here we examined if the changes in brain anatomy produced by blindness alter the patterns of anatomical variation found in the sighted. We derived eight measures of central Visual Pathway anatomy from a structural image of the brain from 59 sighted and 53 blind people. These measures showed highly significant differences in mean size between the sighted and blind cohorts. When we examined the measurements across individuals within each group we found three clusters of correlated variation, with V1 surface area and pericalcarine volume linked, and independent of the thickness of V1 cortex. These two clusters were in turn relatively independent of the volumes of the optic chiasm and lateral geniculate nucleus. This same pattern of variation in Visual Pathway anatomy was found in the sighted and the blind. Anatomical changes within these clusters were graded by the timing of onset of blindness, with those subjects with a post-natal onset of blindness having alterations in brain anatomy that were intermediate to those seen in the sighted and congenitally blind. Many of the blind and sighted subjects also contributed functional MRI measures of cross-modal responses within Visual cortex, and a diffusion tensor imaging measure of fractional anisotropy within the optic radiations and the splenium of the corpus callosum. We again found group differences between the blind and sighted in these measures. The previously identified clusters of anatomical variation were also found to be differentially related to these additional measures: across subjects, V1 cortical thickness was related to cross-modal activation, and the volume of the optic chiasm and lateral geniculate was related to fractional anisotropy in the Visual Pathway. Our findings show that several of the structural and functional effects of blindness may be reduced to a smaller set of dimensions. It also seems that the changes in the brain that accompany blindness are on a continuum with normal variation found in the sighted.
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patterns of individual variation in Visual Pathway structure and function in the sighted and blind
bioRxiv, 2016Co-Authors: G.k. Aguirre, Omar H. Butt, Kate E Watkins, Holly Bridge, Ritobrato Datta, Noah C. Benson, Artur V Cideciyan, Sashank Prasad, Samuel G Jacobson, Aleksandra S. DainAbstract:Many structural and functional brain alterations accompany blindness. In normally sighted people, there is correlated individual variation in some Visual Pathway structures. Here we examined if the changes in brain anatomy produced by blindness alter this pattern of variation. We derived eight measures of central Visual Pathway anatomy from an MPRAGE image of the brain from 59 sighted and 53 blind people. These measures showed highly significant differences in mean size between the sighted and blind cohorts. When we examined the measurements across individuals within each group, we found three clusters of correlated variation, with V1 surface area and pericalcarine volume linked, and independent of the thickness of V1 cortex. These two clusters were in turn relatively independent of the volumes of the optic chiasm and lateral geniculate nucleus. This same pattern of variation in Visual Pathway anatomy was found in the sighted and the blind. Anatomical changes within these clusters were graded by the duration of blindness, with those subjects with a post-natal onset of blindness having alterations in brain anatomy that were intermediate to those seen in the sighted and congenitally blind. Many of the blind and sighted subjects also contributed BOLD fMRI measures of cross-modal responses within Visual cortex, and a diffusion tensor imaging measure of fractional anisotropy within the optic radiations and the splenium of the corpus callosum. We again found group differences between the blind and sighted in these measures. The previously identified clusters of anatomical variation were also found to be differentially related to these additional measures: across subjects, V1 cortical thickness was related to cross-modal activation, and the volume of the optic chiasm and lateral geniculate was related to fractional anisotropy in the Visual Pathway. Our findings show that several of the structural and functional effects of blindness may be reduced to a smaller set of dimensions. It also seems that the changes in the brain that accompany blindness are on a continuum with normal variation found in the sighted.
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Patterns of individual variation in Visual Pathway structure and function in the sighted and blind
PLoS ONE, 2016Co-Authors: G.k. Aguirre, Omar H. Butt, Kate E Watkins, Holly Bridge, Ritobrato Datta, Noah C. Benson, Artur V Cideciyan, Sashank Prasad, Samuel G Jacobson, Aleksandra S. DainAbstract:Patterns of individual variation in Visual Pathway structure and function in the sighted and blind. , .
J.a. Baro - One of the best experts on this subject based on the ideXlab platform.
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A Defective Visual Pathway in Children with Reading Disability
The New England Journal of Medicine, 1993Co-Authors: S Lehmkuhle, Tom Hash, R P Garzia, L Turner, J.a. BaroAbstract:Background The possibility that reading disability in children is associated with Visual problems is in dispute. We sought to test the existence of this association by using electrophysiologic techniques to measure the processing of Visual information in the magnicellular and parvicellular Visual Pathways of the brain. Methods Visual evoked potentials were measured with scalp electrodes in children 8 to 11 years old who were normal readers and in those with reading disability. The potentials were measured for targets with low (0.5 cycle per degree of Visual angle) and high (4.5 cycles per degree) spatial frequency, surrounded by either a steady background or a uniform-field flickering 12 times per second. A flickering field normally reduces the amplitude and increases the latency of a transient potential evoked by a low-spatial-frequency target, which preferentially excites the magnicellular Visual Pathway, but has little effect on the response to a high-spatial-frequency target. Results With a steady bac...
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A defective Visual Pathway in children with reading disability [see comments]
N Engl J Med, 1993Co-Authors: S Lehmkuhle, Tom Hash, R P Garzia, L Turner, J.a. BaroAbstract:BACKGROUND. The possibility that reading disability in children is associated with Visual problems is in dispute. We sought to test the existence of this association by using electrophysiologic techniques to measure the processing of Visual information in the magnicellular and parvicellular Visual Pathways of the brain. METHODS. Visual evoked potentials were measured with scalp electrodes in children 8 to 11 years old who were normal readers and in those with reading disability. The potentials were measured for targets with low (0.5 cycle per degree of Visual angle) and high (4.5 cycles per degree) spatial frequency, surrounded by either a steady background or a uniform-field flickering 12 times per second. A flickering field normally reduces the amplitude and increases the latency of a transient potential evoked by a low- spatial-frequency target, which preferentially excites the magnicellular Visual Pathway, but has little effect on the response to a high-spatial-frequency target. RESULTS. With a steady background, the latencies of the early components (N1 and P1) of the Visual evoked potentials were longer in the reading-disabled children than in the normal readers when the low-spatial-frequency target was used, but not when the high-spatial-frequency target was used. In normal readers, the flickering background increased the latency and reduced the amplitude of the early components, whereas in the reading-disabled children only the amplitude was affected. No differences were observed in either group with the high-spatial-frequency target. CONCLUSIONS. The pattern of results suggests that the response of the magnicellular Visual Pathway is slowed in reading-disabled children, who do not, however, have a general slowing of the Visual response. The possibility that there is a cause-and-effect relation between these findings and reading disability will require further study.
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A defective Visual Pathway in children with reading disability.
The New England Journal of Medicine, 1993Co-Authors: S Lehmkuhle, Tom Hash, R P Garzia, L Turner, J.a. BaroAbstract:BACKGROUND: The possibility that reading disability in children is associated with Visual problems is in dispute. We sought to test the existence of this association by using electrophysiologic techniques to measure the processing of Visual information in the magnicellular and parvicellular Visual Pathways of the brain. METHODS: Visual evoked potentials were measured with scalp electrodes in children 8 to 11 years old who were normal readers and in those with reading disability. The potentials were measured for targets with low (0.5 cycle per degree of Visual angle) and high (4.5 cycles per degree) spatial frequency, surrounded by either a steady background or a uniform-field flickering 12 times per second. A flickering field normally reduces the amplitude and increases the latency of a transient potential evoked by a low-spatial-frequency target, which preferentially excites the magnicellular Visual Pathway, but has little effect on the response to a high-spatial-frequency target. RESULTS: With a steady background, the latencies of the early components (N1 and P1) of the Visual evoked potentials were longer in the reading-disabled children than in the normal readers when the low-spatial-frequency target was used, but not when the high-spatial-frequency target was used. In normal readers, the flickering background increased the latency and reduced the amplitude of the early components, whereas in the reading-disabled children only the amplitude was affected. No differences were observed in either group with the high-spatial-frequency target. CONCLUSIONS: The pattern of results suggests that the response of the magnicellular Visual Pathway is slowed in reading-disabled children, who do not, however, have a general slowing of the Visual response. The possibility that there is a cause-and-effect relation between these findings and reading disability will require further study.
G.k. Aguirre - One of the best experts on this subject based on the ideXlab platform.
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patterns of individual variation in Visual Pathway structure and function in the sighted and blind
PLOS ONE, 2016Co-Authors: G.k. Aguirre, Omar H. Butt, Kate E Watkins, Holly Bridge, Ritobrato Datta, Noah C. Benson, Artur V Cideciyan, Sashank Prasad, Samuel G Jacobson, Aleksandra S. DainAbstract:Many structural and functional brain alterations accompany blindness, with substantial individual variation in these effects. In normally sighted people, there is correlated individual variation in some Visual Pathway structures. Here we examined if the changes in brain anatomy produced by blindness alter the patterns of anatomical variation found in the sighted. We derived eight measures of central Visual Pathway anatomy from a structural image of the brain from 59 sighted and 53 blind people. These measures showed highly significant differences in mean size between the sighted and blind cohorts. When we examined the measurements across individuals within each group we found three clusters of correlated variation, with V1 surface area and pericalcarine volume linked, and independent of the thickness of V1 cortex. These two clusters were in turn relatively independent of the volumes of the optic chiasm and lateral geniculate nucleus. This same pattern of variation in Visual Pathway anatomy was found in the sighted and the blind. Anatomical changes within these clusters were graded by the timing of onset of blindness, with those subjects with a post-natal onset of blindness having alterations in brain anatomy that were intermediate to those seen in the sighted and congenitally blind. Many of the blind and sighted subjects also contributed functional MRI measures of cross-modal responses within Visual cortex, and a diffusion tensor imaging measure of fractional anisotropy within the optic radiations and the splenium of the corpus callosum. We again found group differences between the blind and sighted in these measures. The previously identified clusters of anatomical variation were also found to be differentially related to these additional measures: across subjects, V1 cortical thickness was related to cross-modal activation, and the volume of the optic chiasm and lateral geniculate was related to fractional anisotropy in the Visual Pathway. Our findings show that several of the structural and functional effects of blindness may be reduced to a smaller set of dimensions. It also seems that the changes in the brain that accompany blindness are on a continuum with normal variation found in the sighted.
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patterns of individual variation in Visual Pathway structure and function in the sighted and blind
bioRxiv, 2016Co-Authors: G.k. Aguirre, Omar H. Butt, Kate E Watkins, Holly Bridge, Ritobrato Datta, Noah C. Benson, Artur V Cideciyan, Sashank Prasad, Samuel G Jacobson, Aleksandra S. DainAbstract:Many structural and functional brain alterations accompany blindness. In normally sighted people, there is correlated individual variation in some Visual Pathway structures. Here we examined if the changes in brain anatomy produced by blindness alter this pattern of variation. We derived eight measures of central Visual Pathway anatomy from an MPRAGE image of the brain from 59 sighted and 53 blind people. These measures showed highly significant differences in mean size between the sighted and blind cohorts. When we examined the measurements across individuals within each group, we found three clusters of correlated variation, with V1 surface area and pericalcarine volume linked, and independent of the thickness of V1 cortex. These two clusters were in turn relatively independent of the volumes of the optic chiasm and lateral geniculate nucleus. This same pattern of variation in Visual Pathway anatomy was found in the sighted and the blind. Anatomical changes within these clusters were graded by the duration of blindness, with those subjects with a post-natal onset of blindness having alterations in brain anatomy that were intermediate to those seen in the sighted and congenitally blind. Many of the blind and sighted subjects also contributed BOLD fMRI measures of cross-modal responses within Visual cortex, and a diffusion tensor imaging measure of fractional anisotropy within the optic radiations and the splenium of the corpus callosum. We again found group differences between the blind and sighted in these measures. The previously identified clusters of anatomical variation were also found to be differentially related to these additional measures: across subjects, V1 cortical thickness was related to cross-modal activation, and the volume of the optic chiasm and lateral geniculate was related to fractional anisotropy in the Visual Pathway. Our findings show that several of the structural and functional effects of blindness may be reduced to a smaller set of dimensions. It also seems that the changes in the brain that accompany blindness are on a continuum with normal variation found in the sighted.
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Patterns of individual variation in Visual Pathway structure and function in the sighted and blind
PLoS ONE, 2016Co-Authors: G.k. Aguirre, Omar H. Butt, Kate E Watkins, Holly Bridge, Ritobrato Datta, Noah C. Benson, Artur V Cideciyan, Sashank Prasad, Samuel G Jacobson, Aleksandra S. DainAbstract:Patterns of individual variation in Visual Pathway structure and function in the sighted and blind. , .
Pablo Villoslada - One of the best experts on this subject based on the ideXlab platform.
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The Visual Pathway as a model to understand brain damage in multiple sclerosis
Multiple Sclerosis Journal, 2014Co-Authors: Elena H. Martinez-lapiscina, Bernardo Sanchez-dalmau, Elena Fraga-pumar, Santiago Ortiz-perez, Ana Tercero-uribe, Ruben Torres-torres, Pablo VillosladaAbstract:Patients with multiple sclerosis (MS) almost always experience effects in the Visual Pathway; and thus, Visual dysfunction is not only common but also highly relevant. The Visual Pathway represents a model of acute focal central nervous system (CNS) damage, through acute optic neuritis and retinal periphlebitis, as well as a model of chronic, diffuse CNS damage through chronic retinopathy and optic neuropathy. The optic Pathway can be accurately evaluated in detail, due to the availability of highly sensitive imaging techniques (e.g. magnetic resonance imaging or optical coherent tomography) or electrophysiological tests (multifocal Visual evoked potentials or electroretinography). These techniques allow the interactions between the different processes at play to be evaluated, such as inflammation, demyelination, axonal damage and neurodegeneration. Moreover, these features mean that the Visual Pathway can be used as a model to test new neuroprotective or regenerative therapies.
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lesions in the posterior Visual Pathway promote trans synaptic degeneration of retinal ganglion cells
PLOS ONE, 2014Co-Authors: Johannes Keller, Bernardo Sanchezdalmau, Pablo VillosladaAbstract:Objective Retrograde trans-synaptic degeneration of retinal ganglion cell layer (GCL) has been proposed as one of the mechanisms contributing to permanent disability after Visual Pathway damage. We set out to test this mechanism taking advantage of the new methods for imaging the macula with high resolution by optical coherence tomography (OCT) in patients with lesions in the posterior Visual Pathway. Additionally, we explored the association between thinning of GCL as an imaging marker of Visual impairment such as Visual field defects. Methods Retrospective case note review of patients with retrogeniculate lesions studied by spectral domain OCT of the macula and quadrant pattern deviation (PD) of the Visual fields. Results We analysed 8 patients with either hemianopia or quadrantanopia due to brain lesions (stroke = 5; surgery = 2; infection = 1). We found significant thinning of the GCL in the projecting sector of the retina mapping to the brain lesion. Second, we found strong correlation between the PD of the Visual field quadrant and the corresponding macular GCL sector for the right (R = 0.792, p<0.001) and left eyes (R = 0.674, p<0.001). Conclusions The mapping between lesions in the posterior Visual Pathway and their projection in the macula GCL sector corroborates retrograde trans-synaptic neuronal degeneration after brain injury as a mechanism of damage with functional consequences. This finding supports the use of GCL thickness as an imaging marker of trans-synaptic degeneration in the Visual Pathway after brain lesions.
Kyousuke Kamada - One of the best experts on this subject based on the ideXlab platform.
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intraoperative monitoring of cortically recorded Visual response for posterior Visual Pathway
Journal of Neurosurgery, 2010Co-Authors: Kensuke Kawai, Kyousuke Kamada, Nobuhito SaitoAbstract:Object Intraoperative monitoring of Visual evoked potentials (VEPs) has been regarded as having limited significance for the preservation of Visual function during neurosurgical procedures, mainly due to its poor spatial resolution and signal-to-noise ratio. The authors evaluated the usefulness of cortically recorded VEPs, instead of the usual scalp VEPs, as intraoperative monitoring focusing on the posterior Visual Pathway. Methods In 17 consecutive patients who underwent microsurgical procedures for lesions near the posterior Visual Pathway, cortical responses were recorded using 1-Hz flashing light-emitting diodes and subdural strip electrodes after induction of general anesthesia with sevoflurane or propofol. The detectability and waveform of the initial response, stability, and changes during microsurgical manipulations were analyzed in association with the position of electrodes and postoperative changes in Visual function. Results Initial VEPs were detected in 82% of all patients. The VEPs were det...
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functional monitoring for Visual Pathway using real time Visual evoked potentials and optic radiation tractography
Neurosurgery, 2005Co-Authors: Kyousuke Kamada, Tomoki Todo, Akio Morita, Yoshitaka Masutani, S Aoki, Kensuke Kawai, Takaaki KirinoAbstract:OBJECTIVE: It has been difficult to obtain anatomic and functional information about the Visual Pathway during neurosurgical operations. The aim of this study was to combine the information of the Visual evoked potentials (VEPs) and the anatomic navigation of the optic radiation by diffusion tensor imaging-based tractography for functional monitoring of the Visual Pathway. METHODS: The subjects were two patients with brain lesions adjacent to the Visual Pathway. Diffusion tensor imaging-based tractography of the optic radiation was performed by selecting appropriate regions of interest and by fractional anisotropy. During surgery, cortical VEPs were recorded continuously under general anesthesia with sevoflurane. In Patient 2, the results of optic radiation tractography were imported to a neuronavigation system to better understand the spatial relationships between the lesions and the Visual Pathway (functional neuronavigation). RESULTS: In Patient 1, the lesion did not seem to be attached to the optic radiation, and VEP profiles remained stable during resection. In Patient 2, who had a lesion adjacent to the posterior horn of the lateral ventricle, VEPs suddenly diminished when resection reached the optic radiation as illustrated on the neuronavigation system. As a result, complete left hemianopia developed after surgery in Patient 2. CONCLUSION: We confirmed functional correlations of the results of diffusion tensor imaging-based tractography by monitoring intraoperative VEPs. The combination of continuous VEP and optic-radiation tractography is reliable to monitor the Visual function and is helpful in performing neurosurgical planning near the Visual Pathway.
