Restorative Neurology and Neuroscience - Volume 26, issue 4-5

Authors: Werth, Reinhard

Article Type: Research Article

Abstract: This paper explores whether the child's visual system is more or less vulnerable than the adult's visual system, whether the capacity of the child's visual system to recover from cerebral blindness exceeds the capacity of the adult's, and which brain structures can mediate visual functions after damage to the geniculostriate visual system. Reports about the development of visual functions in normal and in visually-deprived children and about the recovery of visual functions after incomplete damage to …the occipital lobe, unilateral hemispherectomy, and in the absence of both cerebral hemispheres in early life, are reviewed. In addition, 2 new cases are reported. A child (patient 1) is described, who was blindfolded, but had normal visual experience for 2 hours daily between the 24 and the 30 months of age. Despite the daily visual experience, there was an elevation of the luminance difference threshold (LDT) in the periphery of the visual field. An adult patient (patient 2) showed a special mode of "blindsight" that may be present in brain damaged children but that cannot be tested in young children. This patient was always able to detect targets correctly only by "feeling" their presence without actually seeing them. After damage to the geniculostriate system, lost visual functions reappeared in more than half of the children during visual-field training. In many children, the enlargement of the visual field exceeded the enlargement that was reported in hemianopic adults during visual-field training. In rare cases, visual targets were reliably detected in both visual hemifields, even after hemispherectomy. Show more

Citation: Restorative Neurology and Neuroscience, vol. 26, no. 4-5, pp. 377-389, 2008

Authors: Schumacher, Eric H. | Jacko, Julie A. | Primo, Susan A. | Main, Keith L. | Moloney, Kevin P. | Kinzel, Erin N. | Ginn, Jimmy

Article Type: Research Article

Abstract: Purpose: Neural evidence exists for cortical reorganization in human visual cortex in response to retinal disease. Macular degeneration (MD) causes the progressive loss of central visual acuity. To cope with this, MD patients often adopt a preferred retinal location (PRL, i.e., a functional retinal area in their periphery used to fixate instead of the damaged fovea). The use of a PRL may foster cortical reorganization. Methods: We used fMRI to measure brain activity in calcarine …sulcus while visually stimulating peripheral visual regions in MD patients and age-matched control participants. Results: We found that visual stimulation of the PRL in MD patients increased brain activity in cortex normally representing central vision relative to visual stimulation of a peripheral region outside the patients' PRL and relative to stimulation in the periphery of age-matched control participants. Conclusions: These data directly link cortical reorganization in MD to behavioral adaptations adopted by MD patients. These results not only confirm that large-scale cortical reorganization of visual processing occurs in humans in response to retinal disease, but also relate this reorganization to functional changes in patient behavior. Show more

Keywords: Plasticity, cortical reorganization, functional neuroimaging, fMRI, calcarine sulcus, primary visual cortex, retinal disease

Citation: Restorative Neurology and Neuroscience, vol. 26, no. 4-5, pp. 391-402, 2008

Authors: Gudlin, Julia | Mueller, Iris | Thanos, Solon | Sabel, Bernhard A.

Article Type: Research Article

Abstract: Purpose: Several studies have shown that computer-based visual stimulation improves detection performance in brain damaged patients with post-chiasmatic lesions after stroke or trauma. Because it is not known whether visual field defects after retinal lesions can also be modified by visual stimulation we explored if visual field enlargements are possible in patients with glaucoma. Methods: Five patients with primary open angle glaucoma (POAG) performed Vision Restoration Training (VRT), a computer-based vision training …for a total of 6 months in two 3-months blocks with a 3-months training-free interval between the two training periods. Perimetric testing was performed with High Resolution Perimetry (HRP) as well as with 30° and 70° white/white (W/W) and 30° blue/yellow (B/Y) conventional automatic perimetry (Oculus Twinfield). Results: After the first 3 months of training the average detection performance significantly increased in HRP (Z = -2.023, p < 0.05) and in 30° W/W perimetry (Z = -2.023, p < 0.05), but not in B/Y perimetry (Z = -1.214, p = 0.225) or in the 70° W/W perimetry, which included more peripheral, non-trained areas (Z = -0.406, p = 0.684). Visual improvements remained stable after the training-free interval. Measured by HRP after the second VRT period 3 patients achieved an increase in the ability to detect visual stimuli, however, this improvement did not reach significance (Z = -1.826, p = 0.068). Conclusions: While a small patient sample does not permit general conclusions on visual field recovery after glaucoma, this pilot study suggests that visual field defects caused by retinal lesion may be improved by systematic vision stimulation. A larger sample, randomized clinical trial is now warranted. Show more

Keywords: Glaucoma, visual field, visual field stimulation, visual field recovery

Citation: Restorative Neurology and Neuroscience, vol. 26, no. 4-5, pp. 403-412, 2008

Authors: Polat, Uri

Article Type: Research Article

Abstract: Amblyopia is a reduction of visual functions that cannot be attributed directly to the effect of any structural abnormality of the eye or the posterior visual pathway. It is caused by abnormal binocular visual experience early in life, during the 'critical period' that prevents normal development of the visual system. It is widely accepted that therapy can only be effective during the critical period, and that it is not administered after the first decade of life. …Here we provide an overview describing a recent finding of visual abnormalities in amblyopia and propose a treatment that we developed based on this finding. Both previous and new results that are presented here clearly show the success of the structured method, targeted at the specific deficiencies in amblyopia, to improve vision in children and adults. Our results suggest that the training was successful in rejuvenating the visual system and in restoring lost development from the sensory obstacle period. It is possible that the perceptual learning method used here can be applied to other sensory and non-sensory brain modules suffering from developmental problems. Show more

Keywords: Amblyopia, plasticity, lateral interactions, treatment of amblyopia, contrast sensitivity, perceptual learning, neuroplasticity

Citation: Restorative Neurology and Neuroscience, vol. 26, no. 4-5, pp. 413-424, 2008

Authors: Mitchell, Donald E.

Article Type: Research Article

Abstract: Purpose: To review work on animal models of deprivation amblyopia that points to a special role for binocular visual input in the development of spatial vision and as a component of occlusion (patching) therapy for amblyopia. Methods: The studies reviewed employ behavioural methods to measure the effects of various early experiential manipulations on the development of the visual acuity of the two eyes. Results: Short periods of concordant binocular input, if continuous, …can offset much longer daily periods of monocular deprivation to allow the development of normal visual acuity in both eyes. It appears that the visual system does not weigh all visual input equally in terms of its ability to impact on the development of vision but instead places greater weight on concordant binocular exposure. Experimental models of patching therapy for amblyopia imposed on animals in which amblyopia had been induced by a prior period of early monocular deprivation, indicate that the benefits of patching therapy may be only temporary and decline rapidly after patching is discontinued. However, when combined with critical amounts of binocular visual input each day, the benefits of patching can be both heightened and made permanent. Conclusions: Taken together with demonstrations of retained binocular connections in the visual cortex of monocularly deprived animals, a strong argument is made for inclusion of specific training of stereoscopic vision for part of the daily periods of binocular exposure that should be incorporated as part of any patching protocol for amblyopia. Show more

Keywords: Amblyopia, visual deprivation, critical period, plasticity, visual acuity, stereopsis, binocular vision, patching

Citation: Restorative Neurology and Neuroscience, vol. 26, no. 4-5, pp. 425-434, 2008

Authors: Achtman, R.L. | Green, C.S. | Bavelier, D.

Article Type: Research Article

Abstract: Purpose: Adult brain plasticity, although possible, is often difficult to elicit. Training regimens in adults can produce specific improvements on the trained task without leading to general enhancements that would improve quality of life. This paper considers the case of playing action video games as a way to induce widespread enhancement in vision. Conclusions: We review the range of visual skills altered by action video game playing as well as the game components important in promoting …visual plasticity. Further, we discuss what these results might mean in terms of rehabilitation for different patient populations. Show more

Keywords: Video games, perceptual learning, plasticity, visual attention, rehabilitation

Citation: Restorative Neurology and Neuroscience, vol. 26, no. 4-5, pp. 435-446, 2008